Ld Output Formaatin Binary Optiot

GNU linkkeri ld on tarkoitettu kattamaan laajan valikoiman tilanteita ja olla mahdollisimman yhteensopiva muiden linkkerien kanssa. Tämän seurauksena sinulla on monia valintoja sen käyttäytymisen hallitsemiseksi. Tässä on yhteenveto vaihtoehdoista, joita voit käyttää ld: ssä komentoriviltä. Tämä lukuisia komentorivivalintoja saattaa tuntua uhkaavalta, mutta varsinaisessa käytännössä niitä harvoissa käytetään missä tahansa erityisessä yhteydessä. Esimerkiksi ld: n usein käytetty käyttö on yhdistää standardi Unix - objektitiedostoja tavalliseen, tuettuun Unix-järjestelmään On tällainen järjestelmä linkittää tiedoston hello o. Tämä kertoo ld tuottaa tiedoston nimeltään tuotos seurauksena linkittää tiedosto lib crt0 o hello o ja kirjaston libc a jotka tulevat standardi haku hakemistoja Katso keskustelua Alla oleva - l-vaihtoehto. Ld: n komentorivivaihtoehdot voidaan määrittää mistä tahansa järjestyksessä, ja ne voidaan toistaa toistuvasti. Useimpien vaihtoehtojen toistaminen usealla eri argumentilla joko ei ole enää vaikutusta tai ohittaa aiemmat esiintymät komento lin E). Poikkeukset - joita voidaan mielekkäästi käyttää useammin kuin kerran - ovat - A - b tai sen synonyymi - format, - defsym - L - l-R - u ja - tai sen synonyymi - start-ryhmä. Komponenttiyhteyteen liitettyjen objektitiedostojen luettelo, jota voidaan näyttää objfile-muodossa, voi seurata, edeltää tai sekoittaa komentorivivalintoihin, paitsi että vaihtoehtoa ja sen argumenttia ei saa sijoittaa objfile-argumenttiin. Yhteensä linkkeri kutsutaan Jossa on vähintään yksi objektitiedosto, mutta voit määrittää muita binaaritiedostojen muotoja - l - R ja komentosarjan komentokielen avulla. Jos binääritiedostoja ei ole lainkaan määritetty, linkkeri ei tuota mitään tuottoa ja antaa viestin No Syöttötiedostot. Jos linkkeri ei pysty tunnistamaan objektitiedoston muotoa, se olettaa, että se on linkkikoodi Tällä tavalla määritetty komentosarja lisää linkin käyttämää linkin pääasiallista linkkeri-komentosarjaa joko oletusarvoisen linkkikoodin tai käyttäen - T Tämä ominaisuus sallii linkittäjän linkittää tiedostoon, joka näyttää olevan obje ct tai arkisto, mutta itse asiassa vain määrittelee joitain symboliarvoja tai käyttää INPUT: tä tai GROUP: tä muiden kohteiden lataamiseen Katso osa Command Language. For optiot, joiden nimet ovat yksi kirjain, vaihtoehtoisten argumenttien on joko noudatettava option kirjainta puuttumatta välilyönniksi tai oltava Annetaan erillisinä argumentteina välittömästi sen edellyttämän vaihtoehdon jälkeen. Jos vaihtoehtoja, joiden nimet ovat useampia kirjaimia, joko yksi tai kaksi voi edeltää vaihtoehtoa, esimerkiksi --oformat ja - oformat ovat vastaavia. erotetaan vaihtoehdon nimestä yhtäläisellä merkillä tai annetaan erillisinä argumentteina välittömästi sen vaatiman vaihtoehdon jälkeen. Esimerkiksi --oformat srec ja --oformat srec ovat vastaavia. Monimerkkisten vaihtoehtojen nimet lyhenevät. - b - tulostusformaatti ld voidaan konfiguroida tukemaan useampaa kuin yhtä erilaista objektitiedostoa Jos ld on määritetty tällä tavalla, voit käyttää - b-asetusta binäärimuodossa Jotka käyttävät tätä vaihtoehtoa komentorivillä. Vaikka ld on määritetty tukemaan vaihtoehtoisia esitysmuotoja, sinun ei tarvitse yleensä määrittää tätä, koska ld: n pitäisi olla määritetty oletuksena oletusmuodoksi, joka on tavallisin formaatti kussakin koneen syöttöformaatti on tekstijono, BFD-kirjastojen tukema tietyn muotoinen nimi Voit luetella käytettävissä olevat binäärimuodot objdump - i - formaatin syöttöformaatilla on sama vaikutus kuin skriptikomento TARGET Katso luku BFD Voit halutessasi käyttää tätä vaihtoehtoa, jos yhdistät tiedostoja epätavallisella binäärimuodolla Voit myös käyttää - b vaihtaa tiedostomuotoja nimenomaisesti yhdistettäessä erilaisia ​​formaatteja sisältäviä objektitiedostoja sisällyttämällä - b - tulostusmuoto ennen jokaista objektitiedostojen ryhmää Erityinen muoto Oletusmuoto on otettu ympäristömuuttujasta GNUTARGET Voit myös määrittää tulomuodon komentosarjan avulla käyttämällä TARGET-komentoa, katso osaa Optio-komennot - Bstatic Älä linkitä jaettua kirjastot Tämä on vain merkityksellistä alustoille, joilla jaettuja kirjastoja tuetaan - Dynaaminen linkki dynaamisia kirjastoja varten Tämä on vain merkityksellistä alustoille, joilla jaettuja kirjastoja tuetaan Tämä vaihtoehto on yleensä oletus tällaisilla alustoilla - Symbolinen Luodaan jaettu kirjasto Globaaleihin symboleihin jaettuun kirjastoon määritelmään, jos sellainen on, Normaalisti on mahdollista, että yhteiseen kirjastoon yhdistetty ohjelma ohittaa määritelmän jaetun kirjaston sisällä Tämä vaihtoehto on vain merkityksellinen ELF-alustoilla, jotka tukevat jaettuja kirjastoja - c MRI - commandfile Yhteensopivuus MRI: n tuottamien linkkereiden kanssa ld hyväksyy komentotiedostot, jotka on kirjoitettu vaihtoehtoiseen, rajoitettuun komentokieliin, joka on kuvattu osassa MRI Compatible Script Files Esitä MRI-komentotiedostot, joissa on - c - vaihtoehto käyttämällä - T-vaihtoehtoa yleiskäyttöinen ld-skriptauskieli Jos MRI-cmdfilea ei ole olemassa, ld etsii sitä erityisissä hakemistoissa Kaikkien - L-vaihtoehtojen - d - dc - dp avulla Nämä kolme vaihtoehtoa ovat vastaavia useita lomakkeita, joita tuetaan yhteensopivuuden muiden linkkereiden kanssa. Ne jakavat tilaa tavallisille symboleille, vaikka uudelleensijoitettava ulostulostiedosto määritetään - r-komennolla FORCECOMMONALLOCATION on sama Vaikutus Katso kohta Optio Komennot - defsym-symboli-ilmentymä Luo maailmanlaajuinen symboli tuotos-tiedostossa, joka sisältää lausekkeen absoluuttisen osoitteen Voit käyttää tätä vaihtoehtoa niin monta kertaa kuin on tarpeen useiden symbolien määrittelemiseksi komentorivillä Rajoitettua aritmeettimuotoa tuetaan lausekkeen tässä yhteydessä voit antaa heksadesimaalivakion tai olemassa olevan symbolin nimen tai käyttää ja - lisätä tai vähentää heksadesimaalisia vakiot tai symbolit. Jos tarvitset tarkempia lausekkeita, harkitse linkkikomentokielen käyttämistä käsikirjoituksesta. katso osa Tehtävä Symbolien määrittäminen Huomaa ei saa olla välilyöntiä yhtäläisen merkin välissä olevan symbolin ja ilmaisun "embedded-relocs" kanssa Tämä vaihtoehto on käytössä merkityksellistä yhdistettäessä MIPS-upotettua PIC-koodia, jonka - membedded-pic - vaihtoehto tuottaa GNU-kääntäjälle ja asentajalle. Se saa linkkeriä luomaan taulukon, jota voidaan käyttää ajon aikana siirtää kaikki tiedot, jotka on staattisesti alustettu osoittimien arvoihin. Koodia testsuite ld-empic - tietokohdassa - e entry Käytä merkintää nimenomaisena symbolina ohjelman alkuun suorittamisen sijaan oletusarvon syöttökohdaksi Katso kohta Entry Point keskustelusta oletusarvoista ja muista syöttökohdan määrittämisen tavoista - F - F-muotoa ei ole otettu huomioon Jotkut vanhat linkit käyttävät tätä vaihtoehtoa kokoelma-työkaluketjussa objektitiedostomuodon määrittämiseksi sekä panos - että lähtöobjekti-tiedostoille. Mekanismit ld käyttävät tätä tarkoitusta varten - b tai - format - asetukset syöttötiedostoille, - formaation vaihtoehdoksi tai TARGET-komento tuotos-tiedostojen linkkikoodeissa GNUTARGET-ympäristömuuttuja on joustavampi, mutta ld hyväksyy F-vaihtoehdon yhteensopivuuden kanssa skriptit, jotka on kirjoitettu soittamaan vanha linkki - muotoinen input-formaatti Synonyymi - b - tulostusformaatti - g Ohitettu Yhteensopivuus muiden työkalujen kanssa - G-arvo - G-arvo Määritä optimoidut objektit maksimissa GP-rekisterin avulla kokoon MIPS ECOFF: n mukaan Muista objektitiedostomuodoista - help Tulosta yhteenveto komentorivin vaihtoehdoista vakiotulosteesta ja poistumisesta - i Suorita inkrementaalinen linkki samalla tavalla kuin option - r - l ar Lisää arkistotiedosto arkistoon linkitetyille tiedostoille Tämä vaihtoehto voidaan käyttää mitä tahansa numeroa kertaa ld etsii sen polku-listan, joka esiintyy lib ar a: lla jokaiselle määritetylle arkistolle - L searchdir - L searchdir Lisää polku searchdir luetteloon poluista, jotka ld etsii arkistokirjastoja ja ld-ohjauskäsikirjoituksia. Voit käyttää tätä vaihtoehtoa minkä tahansa numeron Aikaisia ​​hakemistoja Hakemistot etsitään siinä järjestyksessä, jossa ne on määritetty komentorivillä Hakutekstejä, jotka on määritetty komentorivillä, etsitään ennen oletus hakemistoja Kaikki - L-asetukset koskevat kaikkia - l-vaihtoehtoja riippumatta siitä, missä järjestyksessä E-vaihtoehdot näkyvät. Polut voidaan myös määrittää linkkikoodissa SEARCHDIR-komennolla. Tällä tavalla määritetyt hakemistot etsitään kohdassa, jossa linkkeri-komentosarja ilmestyy komentoriville - M Tulosta standardituotokselle linkkikartta - diagnostiikkatiedot siitä, missä symboleja kartoitetaan ld: llä ja tietoa maailmanlaajuisesta yhteisestä tallennusvarauksesta - Karttahakemisto Tulosta tiedoston karttakansioon linkkikartta - diagnostiikkatiedot siitä, missä symboleja kartoitetaan ld: llä ja tietoa maailmanlaajuisesta yleisestä varastointiallokemuksesta - m emulointi - m emulaatio Emuloida Emulointilinkkeri Voit luetella käytettävissä olevat emulaatiot --verbose - tai - V-vaihtoehdoilla Oletusarvo riippuu siitä, miten ld on määritetty - N Määritä teksti - ja dataosat lukettaviksi ja kirjoitettaviksi Myös älä lajittele sivuosuutta Jos lähdemuoto tukee Unix-tyyppisiä taikuusnumeroita, merkitse ulostulo OMAGIC-n Aseta tekstisegmentti vain luettavaksi ja merkitse ulostulo NMAGIC: ksi, jos se on mahdollista - noinhibit-exec Pidä execu taulukon ulostulotiedosto, kun se on vielä käytettävissä. Normaalisti linkkeri ei tuota tulostustiedostoa, jos se havaitsee virheitä linkkiprosessin aikana, kun se poistuu kirjoittamasta tulostustiedostoa, kun se aiheuttaa virheen. - no-keep-memory ld yleensä optimoi nopeuden Yli muistin käyttö tallentamalla muistitiedostojen symbolitietueita Tämä vaihtoehto kertoo ld: lle sen sijaan, että se optimoi muistin käytön, merkitsemällä symbolit taulukoihin tarpeen mukaan Tämä voi olla tarpeen, jos ld loppuu muistitilasta yhdistettäessä suurta suoritettavaa - o-lähtöä Käytä lähtöä ld: n tuottaman ohjelman nimenä, jos tätä vaihtoehtoa ei ole määritetty, nimiä käytetään oletusarvoisesti. Komentosarjassa OUTPUT voi myös määrittää tulostustiedoston nimen - oformat - ulostemuoto-ld voidaan konfiguroida tukemaan useampaa kuin yhtä tyyppiä Objekti-tiedostosta Jos ld on määritetty tällä tavalla, voit käyttää - oformat-asetusta määrittääksesi binäärimuodon tulostusobjektitiedostoon. Jopa kun ld on määritetty tukemaan vaihtoehtoisia objektimuotoja, y Ou don t yleensä määritellä tämän, koska ld olisi määritettävä tuottamaan oletusmuodon muodossa tavallisin formaatti jokaisen koneen ulostulomuodossa on tekstijono, tietyn muodon nimi, jota BFD-kirjastot tukevat Voit luetella saatavilla olevat binäärimuodot, joissa on objdump - i Script-komento OUTPUTFORMAT voi myös määrittää tulostusmuodon, mutta tämä vaihtoehto ohittaa sen Katso kohta BFD - R tiedostonimi Lue symbolin nimiä ja niiden osoitteita tiedostonimestä, mutta älä siirrä sitä uudelleen tai lisää se lähtöön Tämä mahdollistaa tulostustiedoston viittaavan symbolisesti absoluuttisiin muistiin tallennettuihin muistiin tallennettuihin paikkoihin - relax Yksi vaihtoehto koneeseen vaikuttavilta vaikutuksilta Joillakin alustoilla - relax-vaihtoehto suorittaa globaaleja optimointeja, jotka ovat mahdollisia, kun linkki ratkaisee ohjelman osoittamisen, kuten rentouttava osoite-tilat ja uusien ohjeiden syntetisointi tuotosobjektin tiedostossa - retain-symbolit-tiedoston tiedostonimi Vain tiedostonimen tiedostonimen hylkäämät symbolit Kaikki muut tiedostonimi on yksinkertaisesti litteä tiedosto, jossa on yksi symboli per rivi Tämä vaihtoehto on erityisen käyttökelpoinen ympäristöissä, joissa suuri globaali symbolitietokanta kertyy vähitellen, jotta voidaan säästää aika-aikaista muistia - retain-symbolit-tiedosto ei hylkää määrittelemättömiä symboleja , Tai siirtämiseen tarvittavat symbolit Voit vain määrittää - retain-symbolit-tiedoston kerran komentorivissä Ohittaa ohjesivut - s ja - S - r Luo siirrettävä lähdekoodi - eli tuottaa tulostustiedoston, joka puolestaan ​​voi toimia tulona ld: lle Tämä Jota kutsutaan usein osittaiseksi linkittämiseksi. Sivuvaikutuksena Unix-taika-arvoja tukevissa ympäristöissä tämä vaihtoehto asettaa myös lähtötiedoston s taikuusnumeron OMAGIC: lle. Jos tätä vaihtoehtoa ei ole määritetty, tuotetaan absoluuttinen tiedosto Kun C-ohjelmat yhdistetään, tämä vaihtoehto Ei ratkaise viittauksia konstruktoreihin, käytä - Ur Tämä vaihtoehto toimii samalla tavalla kuin - i - S Ominaa virheenkorjaussymbolin tiedot, mutta ei kaikkia symbolia lähtötiedostosta - Viive kaikki symbolitiedot lähtötiedostosta - shared Luo jaettu kirjasto Tällä hetkellä tuetaan vain ELF - ja SunOS-alustoilla SunOS-linkillä luodaan automaattisesti jaettu kirjasto, jos - e-vaihtoehtoa ei käytetä ja linkissä on määrittelemätön symboli - sort-common Normaalisti, kun ld Sijoittaa maailmanlaajuiset yhteiset symbolit sopiviin ulostuloosiin, lajittelee ne koon mukaan Ensimmäiseksi tulevat kaikki yhden tavun symbolit, sitten kaikki kaksi tavua, sitten kaikki neljä tavua ja sitten kaikki muu Tämä on estää kaavojen välisten aukkojen väliset aukot rajoitukset Tämä asetus poistaa käytöstä, että lajittelu - split-by-reloc-laskenta yrittää luoda ylimääräisiä osioita tulostustiedostoon niin, että tiedostossa ei ole yhtään yksittäistä lähdekoodia enemmän kuin laskea uudelleensijoituksia Tämä on hyödyllistä, kun tuotetaan valtavaa siirrettävää ladattavaksi tiettyihin reaaliaikaisiin ytimiin COFF-objektitiedostomuodolla, koska COFF ei voi edustaa yli 65535 siirtoa yhdessä osassa Huomaa, että tämä ei toimi objektitiedostomuodoilla, jotka eivät tue mielivaltaiset osat Linkkeri ei jakaa yksittäisiä tuloryhmiä uudelleenjakoon, joten jos yksittäinen syöteosuus sisältää enemmän kuin laskusiirrot, yksi lähtöosa sisältää sen, että monet siirrot - split-by-file Samanlainen kuin - split-by-reloc, mutta luo Uusi lähtöosa kustakin tulotiedostosta - tilastot Lasketaan ja näytetään linkkimen toiminnan tilastot, kuten suoritusaika ja muistin käyttö - Tbss org - Tdata org - Teksti-org Käytä org-tietokannan lähtöosoitteen - vastaavasti - bss tiedoston tai tekstisegmentin on oltava yksi heksadesimaalinen kokonaisluku yhteensopivuuteen muiden linkkereiden kanssa, voit jättää johtavan 0x: n, joka yleensä liittyy heksadesimaalisiin arvoihin - T komento-tiedosto komennolla Command Command-komentotiedosto Komentoja korvaavat ld S komentotiedostoa sen sijaan, että se lisätään siihen, joten komentorivillä on määritettävä kaikki, mikä on tarpeellista kuvata kohdemuotoa. Katso osa Command Language Jos komentorivejä ei ole, ld Etsii sitä edellisissä - L-asetuksissa määritetyissä hakemistoissa Kerättävät useampia - T-vaihtoehtoja - t Tulostaa tulosatiedostojen nimet, koska ne käsittelevät niitä perinteisen muodon Joidenkin kohteiden osalta ld: n tulos eroaa tietyllä tavalla Esim. SunOS, ld yhdistää päällekkäiset merkinnät symbolin merkkijono - taulukkoon Tämä voi vähentää tulostustiedoston kokoa täydellä virheenkorjaustiedoilla yli 30 prosentilla Valitettavasti, jos tiedostossa on useita linkkejä, SunOS dbx - ohjelma ei voi lukea tuloksena olevaa ohjelmaa gdb ei ole pulmia - Traditional-format-kytkin kertoo ld: n, ettei yhdistää päällekkäisiä merkintöjä - u symboli Vahvistussymboli kirjoitetaan tulostustiedostoon määrittelemättömänä symbolina Tämä voi esimerkiksi käynnistää Ylimääräisten moduulien liittäminen vakiokirjastoista - u voidaan toistaa useilla eri argumentteilla lisäämään määrittelemättömiä symboleja - Ur Muiden kuin C-ohjelmien osalta tämä vaihtoehto on vastaava Alentuu - r: lle tuottaa siirrettävän lähdön eli tulostiedoston, joka puolestaan ​​voi toimia tulona ld: ksi yhdistettäessä C-ohjelmia, - Ur ratkaisee viittauksia konstruktoreihin, toisin kuin - r Se ei toimi käyttää - Ur tiedostoissa, Itse linkitettiin - Ur, kun konstruktion taulukko on rakennettu, sitä ei voi lisätä Käytä - Ur vain viimeiseen osittaiseen linkkiin ja - r muille --verbose Näytä versionumero ld: lle ja luetella linkitetyt emulaatiot, joita tuetaan Näyttää, mitä syöttötiedostoja voi ja ei voida avata - v - V Näytä ld: n versionumero - V - vaihtoehto myös luetellaan tuetut emulaatiot - versio Näytä versio ld: lle ja exit - warn-common Varoitus, kun yhteinen symboli yhdistetään Toinen yhteinen symboli tai symbolien määritelmä Unix-linkit sallivat tämän hieman hämärän käytännön, mutta linkkereita joissakin muissa käyttöjärjestelmissä ei Tämä vaihtoehto mahdollistaa ongelmien löytämisen maailmanlaajuisten symbolien yhdistämisestä Valitettavasti jotkut C-kirjastot käyttävät tätä käytäntöä, joten saatat saada joitakin varoituksia kirjastojen ja ohjelmien symboleista. Tässä on kolme erilaista maailmanlaajuista symbolia, joita tässä havainnollistaa C esimerkkejä int i 1 Määritelmä, joka menee tulostustiedoston alustettuun tietoosiin extern int i Määrittelemätön viittaus, joka ei anna tilaa. Jokaiselle muuttujalle on määritelmän tai yhteinen symboli. Yhteinen symboli Jos muuttujalle on vain yksi tai useampi tavallinen symboli, se siirtyy muuttujalle jonon int lähtötiedosto Linkkeri yhdistää saman muuttujan useat yhteiset symbolit yhdeksi symboliksi. Jos ne ovat erikokoisia, se valitsee suurimman koon. Linkki muodostaa yhteisen sanoman ilmoitukseksi, jos sama muuttuja on määritelty. - warn - yleinen vaihtoehto voi tuottaa viisi erilaista varoitusta. Kukin varoitus koostuu viivaparista, joista ensimmäinen kuvastaa juuri havaittua symbolia, ja toinen kuvaa edellistä symbolia, jolla on sama nimi O ne tai molemmat näistä symboleista ovat yhteinen symboli. Verkkosymbolin lisääminen referenssiin, koska symboliin on jo määritelmä. Verkkosymbolin lisääminen referenssiin, koska symbolin myöhempi määritelmä on havaittu Tämä on Sama kuin edellinen tapaus, paitsi että symboleja esiintyy eri järjestyksessä. Muodosta yhteinen symboli edellisellä samankokoisella yhteisellä symbolilla. Muodosta yhteinen symboli edellisellä ylemmällä yhteisellä symbolilla. Muodosta yhteinen symboli edellisellä pienemmällä yhteinen symboli Tämä on sama kuin edellinen tapaus, paitsi että symboleja esiintyy eri järjestyksessä.-varoittajat-konstruktorit Varoita, jos käytetään kaikkia globaaleja konstruktoreja Tämä on hyödyllinen vain muutamille objektiedostomuotoille Muodot, kuten COFF tai ELF, linkki ei pysty havaitsemaan maailmanlaajuisten konstruktoreiden käyttöä - warn-once Vain varoittaa kerran jokaiselle määrittelemättömälle symbolle, eikä kerran per moduuli, joka viittaa siihen Jokaiseen komentoriville mainittuun arkistoon, T tiedosto arkiston tiedostossa sen sijaan, että haettaisiin vaadittujen objektitiedostojen arkistoa. Tätä käytetään yleensä arkistointitiedoston vaihtamiseen jaettuun kirjastoon, joka pakottaa jokaisen objektin sisällytettäväksi tuloksena olevaan jaettuun kirjastoon - X Poista kaikki väliaikaiset paikalliset tiedostot symbolit Useimmat kohteet ovat kaikki paikalliset symbolit, joiden nimet alkavat L-x: llä Poista kaikki paikalliset symbolit - y-symboli Tulosta jokaisen linkitetyn tiedoston nimi, johon symboli ilmestyy Tämä vaihtoehto voidaan antaa moneen kertaan Useissa järjestelmissä on välttämätöntä Kopioi aliverkkotunnus Tämä vaihtoehto on hyödyllinen, kun sinulla on määrittelemätön symboli linkissä, mutta et tiedä, mistä viittaus on peräisin - arkistoista - - aloittavien ryhmien arkistoista --end-ryhmästä Arkistojen pitäisi olla luettelo arkistoista Ne voivat olla joko nimenomaisia ​​tiedostonimiä tai - l-vaihtoehtoja. Määritettyjä arkistoja etsitään toistuvasti, kunnes uusia, määrittelemättömiä viitteitä ei luoda. Normaalisti arkisto etsitään vain kerran siinä järjestyksessä kuin se on määritetty komentorivillä Jos arkistossa oleva symboli tarvitaan ratkaisemaan määrittelemätön symboli, jonka kohde viittaa arkistossa, joka ilmestyy myöhemmin komentoriville, linkki ei pysty ratkaisemaan kyseistä viittausta. Ryhmittämällä arkistot etsitään niitä toistuvasti, kunnes kaikki mahdolliset viitteet on ratkaistu Tämän vaihtoehdon käytöllä on merkittävät suorituskykykustannukset. Paras käyttää sitä vain, jos kahden tai useamman arkiston välillä on väistämättömiä pyöreitä viittauksia. Siirry ensimmäiseen edelliseen seuraavaan viimeiseen osioon, sisällysluetteloon. Onko komento - line-asetukset, jotka vakuuttavat gcc: n tuottamaan litteän binääritiedoston itsenäiseltä lähdetiedostolta Esimerkiksi oletetaan, että sisällön sisältö on. Ei ulkoisia viitteitä, mitään viemistä linkkeriin Haluan saada pienen tiedoston vain koneen ohjeet tätä toimintoa varten, ilman muita koristeluja Erilaisia ​​DOS-tiedostoja lukuun ottamatta 32-bittistä suojattua tilaa. asked Lokakuun 30 09 klo 0 26. Muut vastaukset ovat ehdottomasti tapa mennä Kuitenkin minulla oli Määritellä komentorivin argumentteja objcopy jotta minun tuotos on odotettua Huomaa, että olen kehittänyt 32-bittinen koodi 64-bittinen kone, joten - m32 argumentti Pidän myös intel kokoonpano syntaksia paremmin, joten sinun Katso, että myös argumenteissa. Oh, täällä s, jossa minun oli määriteltävä, että nimenomaan halusin vain osion. Minulla oli noin 2 tuntia lukemista ja kokeilemalla erilaisia ​​vaihtoehtoja ennen kuin tajusin tämän. Toivottavasti tämä säästää jonkun toisen tuolloin. Voit siirtää vaihtoehdoista linkkeriin suoraan - Wl-linkkiohjelman kanssa. Asianomaiset dokumentit kopioidaan alla gcc.-Wl: stä, lisävaihtoehto vaihtoehtona linkkeriin. Jos vaihtoehto sisältää pilkuja, se jaetaan useisiin vaihtoehtoihin osoitteessa Pilkkuja Voit käyttää tätä syntaksia argumentin siirtämiseen vaihtoehdolle Esimerkiksi kulkee - Kartta linkkeriin Kun käytät GNU-linkkiä, voit saada myös saman vaikutuksen. Kun kopioit gcc: n kanssa, jos siirrät - Wl: n, - oformat binääri luo binääritiedoston t: n sijaan hän elf - muoto Jos --formati binääri kertoo ld: n generoivan binääritiedoston. Tämä poistaa tarpeen objcopy erikseen. Huomaa, että --oformat binääri voidaan ilmaista OUTPUTFORMAT binaariksi linkkikoodista Jos haluat käsitellä tasomaisia ​​binäärejä, on suuri mahdollisuus, että hyötyisit siitä, että linkkeri-komentosarjat tarjoavat korkean tason. vastannut 6. toukokuuta 14 klo 18 40. Komentokieli antaa selkeän ohjauksen linkkiprosessille, joka mahdollistaa täydellisen määrityksen kartoituksen linkkeri tulotiedostojen ja Sen tuotos ohjaa sisääntulotiedostoja. Tiedostomuodot. tulostustiedoston asettelut. osastojen jakaminen. Yhteisten blokkien jakaminen. Voit toimittaa komentotiedostoa, joka tunnetaan myös linkkikoodina linkkeriin joko nimenomaisesti - T-vaihtoehdon kautta tai implisiittisesti tavallinen tiedosto Jos linkkeri avaa tiedoston, jota se ei tunnista tuettuksi esineeksi tai arkistomuodoksi, se ilmoittaa virheen. ld-komentokieli on lausekkeen kokoelma, jotkut ovat yksinkertaisia ​​avainsanoja, Jotkut valitaan ja ryhmitellään syöttötiedostot tai nimetulostustiedostot ja kahdella lauseketyypillä on perustavanlaatuinen ja kattava vaikutus linkitysprosessiin. Ld-komentokielen perustavanlaatuinen käsky on SECTIONS-komento, ks. Luku Lähtöosuuksien määrittäminen Jokainen Merkityksellisellä komentokirjoitusohjelmalla on oltava SEITSIONI-komento, jossa määritetään kuvan tulostustiedoston s - asettelusta eriasteisissa yksityiskohtiin. Kaikissa tapauksissa ei tarvita muuta komentoa. MEMORY-komento täydentää SECTIAIA kuvaamalla kohdearkkitehtuurin käytettävissä olevaa muistia Tämä komento on Valinnainen, jos et käytä MEMORY-komentoa, ld olettaa, että koko solmussa on riittävästi muistia, katso kohta Muistin ulkoasu. Voit sisällyttää kommentteja linkkeri-komentosarjoihin samalla tavoin kuin C: ssä rajatut ja kuten kohdassa C, kommentit ovat syntaktisesti vastaavia Monia hyödyllisiä komentoja ovat aritmeettiset lausekkeet. Komennon kielen ilmaisujen syntaksi on identtinen C-lausekkeita, joilla on seuraavat ominaisuudet. Kaikki ilmaisut on arvioitu kokonaislukuina ja ovat pitkiä tai ei-allekirjoittamattomia pitkätyyppisiä. Kaikki vakiot ovat kokonaislukuja. Kaikki C-aritmeettiset operaattorit ovat käytettävissä. Voit viitata, määritellä ja luoda globaaleja muuttujia. Voit soittaa erikoistarkoituksiin sisäänrakennetut toiminnot. Integers Integers. Symbols Symboli Names. Location Counter Sijainti Counter. Operators Operators. Evaluation Evaluation. Assignment Assignment Määritä Symbols. Arithmetic Functions Built-in Functions. An oktaali kokonaisluku on 0, jota seuraa nolla tai enemmän oktaaliarvot 01234567.A desimaaliertävä kokonaisluku alkaa nolla-numerolla ja sen jälkeen nollalla tai useammalla numerolla 0123456789.Heksadesimaalinen kokonaisluku on 0x tai 0X, jota seuraa yksi tai useampi heksadesimaaliluku, joka on valittu 0123456789abcdefABCDEF. To kirjoittaa negatiivinen kokonaisluku, käytä etuliitteen operaattoria - katso luku Operators. Additionally, suffiksit K ja M voidaan käyttää skaalaamaan vakio vastaavasti. Esimerkiksi seuraavat kaikki viittaavat samaan määrään. Jollei qu Merkinnät alkavat kirjaimella, alaviivalla tai pisteellä, ja ne voivat sisältää kirjaimia, alaviivoja, numeroita, pisteitä ja väliviivoja. Tarpeeton symbolin nimi ei saa olla ristiriidassa minkä tahansa avainsanan kanssa. Voit määrittää symbolin, joka sisältää parittomia merkkejä tai on sama nimi kuten avainsana, ympäröivällä symbolinimellä kaksoisvetoina. Koska symbolit voivat sisältää monia muita kuin aakkosia, se on turvallisin rajata symboleja välilyönnillä Esimerkiksi AB on yksi symboli, kun taas A - B on ekspressiota, johon liittyy vähennys. erityinen linkkeri muuttuva piste sisältää aina nykyisen ulostulon sijainnin laskurin Koska aina viittaa paikkaan ulostulo-osassa, se on aina näkyvä lausekkeessa SECTIONS-komennossa. Symboli voi näkyä missä tahansa, että tavallinen symboli sallitaan lausekkeessa, mutta sen tehtävät aiheuttavat haittavaikutuksen Symbolin arvon määrittäminen aiheuttaa paikannuslaskurin siirtämisen Tätä voidaan käyttää luomaan reikiä lähtöosiossa Paikkalaskuri ma Y: tä ei voi siirtää taaksepäin. Edellisessä esimerkissä tiedosto1 on sijoitettu aloitusosion alkuun, sitten on 1000-tavuinen aukko. Sitten file2 ilmestyy, myös 1000-tavuisen välin jälkeen, ennen kuin tiedosto3 on ladattu. Merkintä 0x1234 määrittää, mitä tietoja Kirjoittamaan aukkoihin, ks. Osa Valinnainen osiomallit. Liitäntä käyttää lausekkeiden laimeaa arviointia vain laskee lausekkeen, kun se on ehdottoman välttämätöntä. Linkki tarvitsee aloitusosoitteen arvon ja muistipaikkojen pituudet, jotta linkit Kaikki nämä arvot lasketaan mahdollisimman pian, kun linkkeri lukee komentotiedostossa. Muita arvoja, kuten symboliarvoja, ei kuitenkaan ole tiedossa tai tarvittavissa ennen tallennusvarauksen jälkeen. Tällaisia ​​arvoja arvioidaan myöhemmin, kun muita tietoja, kuten lähtöosien koot on käytettävissä symbolien osoituksen ilmaisussa. Voit luoda globaaleja symboleja ja määrittää arvoja osoitteita globaaleihin symboleihin käyttäen mitä tahansa C-osoittamistoimintaa. s Ymbol ilmaisun symboli ilmaisu symboli ilmaisu symboli - ilmaisu symboli ilmaisu symboli ilme. Kaksi tehtävää erottaa osoituksen muilta operaattoreilta ld-ilmaisuina. Osoitetta voidaan käyttää vain lausekkeen juuressa, ab 3 on sallittu, mutta ab 3 on virhe. Sijoittaa jäljellä oleva puolipiste kohdistuslausekkeen lopussa. Lähetyslausekkeet voivat näkyä. Ne käsittävät omat oikeutensa ld-käsikirjoituksessa tai. Ovat erillisiä lausuntoja SECTIONS-komennossa tai osassa osan määrittelyn sisältöä osioissa Kaksi ensimmäistä tapausta ovat samanarvoisia - molemmat määrittävät symbolin, jossa on absoluuttinen osoite. Viimeinen tapaus määrittää symbolin, jonka osoite on suhteessa tiettyyn osaan, ks. Luku Lähtöosuuksien määrittäminen. Kun linkkeri-ilmentymä arvioidaan ja määritetään muuttuja, se annetaan joko absoluuttiseksi tai uudelleensijoittavaksi tyypiksi Absoluuttinen ekspressiotyyppi on sellainen, jossa symboli sisältää arvon, joka sillä on ulos Laita tiedosto uudelleen siirrettäväksi ilmentymistyypiksi on sellainen, jossa arvo ilmaistaan ​​kiinteänä siirtymänä jakson alustasta. Ilmentymän tyyppiä ohjaa sen asema komentosarjatiedostossa. Otsikon määritelmässä määritetty symboli luodaan suhteessa jakson pohja luodaan absoluuttisena symbolina, jolle on määritetty symboli. Koska jaksossa määritetty symboli on suhteessa jakson alustaan, se säilyy siirrettävissä, jos uudelleen siirrettävää lähdettä pyydetään. absoluuttinen arvo, vaikka se määritettäisiin osion määritelmässä käyttämällä absoluuttista osoitustoimintoa ABSOLUTE. Esimerkiksi, luodaan absoluuttinen symboli, jonka osoite on otsikkolohkoryhmän viimeinen tavu. Linkki yrittää siirtää tehtävän arvioinnin kunnes kaikki lähde-ilmaisun termit tunnetaan, ks. luku Evaluation Esimerkiksi kappaleiden kokoja ei voida tunnistaa vasta jakamisen jälkeen, joten tehtävät riippuvat t niitä ei suoriteta, ennen kuin ne on jaettu Jotkut lausekkeet, kuten ne, jotka riippuvat sijainnin laskurin pisteestä, on arvioitava allokoinnin aikana Jos lausekkeen tulos on tarpeen, mutta arvoa ei ole käytettävissä, Script kuten seuraavaksi. Aiheuttaa virheilmoituksen Ei-vakio-lauseketta aloitusosoitetta varten. Joissakin tapauksissa on toivottavaa, että linkkikooderi määrittää symbolin vain, jos se on viitattu, ja vain, jos sitä ei ole määritetty mihinkään Linkki Esimerkiksi perinteiset linkerit määrittelivät symbolin etext ANSI C vaatii kuitenkin, että käyttäjä voi käyttää etextä funktion nimeä virheettömästi PROVIDE-avainsanaa voidaan käyttää määrittelemään symboli, kuten etext vain, jos se on viitattu, mutta ei määritelty Syntaksi on PROVIDE-symboli. Komennon kieli sisältää useita sisäänrakennettuja funktioita, joita käytetään linkkipohjaisissa lausekkeissa. ABSOLUTE exp Return absoluuttinen ei-relocatable, op Lausekkeen lausekkeen ei-negatiiviseen arvoon. Pääsääntöisesti käyttökelpoinen absoluuttisen arvon osoittamiseksi osiin määritelmässä olevaan symboliin, jossa symboliarvot ovat normaalisti osa-suhteinen ADDR-osa. Palauta nimettyjen osien absoluuttinen osoite. Sen kohdan sijainti Seuraavassa esimerkissä symboli1 ja symboli2 ovat identtiset arvot ALIGN exp Palaa nykyisen sijainnin laskurin tuloksiin, joka on kohdistettu seuraavaan exp rajaan exp, on oltava ilmentymä, jonka arvo on kahden teho Tämä vastaa ALIGN-arvoa T muuttaa sijainnin laskurin arvoa - se vain aritmeettisesti sitä Esimerkiksi, kohdistetaan ulostulo-osa seuraavaan 0x2000 tavun rajaan edellisen osan jälkeen ja asetetaan muuttuja osiossa seuraavaan 0x8000-rajaan sen jälkeen, kun syöttöosat Tässä esimerkissä ALIGN-sovelluksen ensimmäinen käyttö määrittää osan sijainnin, koska sitä käytetään osion määritelmän valinnaisena aloitusmääritteenä Ee-osa Valinnaiset osiomääritykset Toinen käyttö määrittelee muuttujan arvon. Sisäänrakennettu NEXT liittyy läheisesti ALIGN DEFINED-symboliin Paluu 1, jos symboli on linkkerin maailmanlaajuisessa symbolitaulukossa ja määritelty, muuten palaa 0 Tätä toimintoa voi käyttää oletusarvot symboleille Esimerkiksi seuraava komentotiedostofragmentti osoittaa, kuinka asettaa maailmanlaajuinen symboli alkamaan ensimmäiselle sijainnille osiossa - mutta jos symboli nimeltä alkava jo on olemassa, sen arvo säilyy NEXT exp Return next Jakamaton osoite, joka on exp monikerta Tämä toiminto liittyy läheisesti ALIGN exp - ohjelmaan, ellet käytä MEMORY-komentoa määrittääksesi epäjatkuvan muistin tulostustiedostoon, kaksi toimintoa ovat vastaava SIZEOF-osa Palauta koko mainitussa osassa tavua has been allocated In the following example, symbol1 and symbol2 are assigned identical values SIZEOFHEADERS sizeofheaders Return the size in bytes of the output file s headers You c an use this number as the start address of the first section, if you choose, to facilitate paging. The linker s default configuration permits allocation of all available memory You can override this configuration by using the MEMORY command The MEMORY command describes the location and size of blocks of memory in the target By using it carefully, you can describe which memory regions may be used by the linker, and which memory regions it must avoid The linker does not shuffle sections to fit into the available regions, but does move the requested sections into the correct regions and issue errors when the regions become too full. A command file may contain at most one use of the MEMORY command however, you can define as many blocks of memory within it as you wish The syntax is name is a name used internally by the linker to refer to the region Any symbol name may be used The region names are stored in a separate name space, and will not conflict with symbols, file names or section names Use distinct names to specify multiple regions attr is an optional list of attributes, permitted for compatibility with the AT T linker but not used by ld beyond checking that the attribute list is valid Valid attribute lists must be made up of the characters LIRWX If you omit the attribute list, you may omit the parentheses around it as well origin is the start address of the region in physical memory It is an expression that must evaluate to a constant before memory allocation is performed The keyword ORIGIN may be abbreviated to org or o but not, for example, ORG len is the size in bytes of the region an expression The keyword LENGTH may be abbreviated to len or l. For example, to specify that memory has two regions available for allocation--one starting at 0 for 256 kilobytes, and the other starting at 0x40000000 for four megabytes. Once you have defined a region of memory named mem you can direct specific output sections there by using a command ending in mem within the SECTIONS com mand see section Optional Section Attributes If the combined output sections directed to a region are too big for the region, the linker will issue an error message. The SECTIONS command controls exactly where input sections are placed into output sections, their order in the output file, and to which output sections they are allocated. You may use at most one SECTIONS command in a script file, but you can have as many statements within it as you wish Statements within the SECTIONS command can do one of three things. define the entry point. assign a value to a symbol. describe the placement of a named output section, and which input sections go into it. You can also use the first two operations--defining the entry point and defining symbols--outside the SECTIONS command see section The Entry Point and see section Assignment Defining Symbols They are permitted here as well for your convenience in reading the script, so that symbols and the entry point can be defined at meaningful points in yo ur output-file layout. If you do not use a SECTIONS command, the linker places each input section into an identically named output section in the order that the sections are first encountered in the input files If all input sections are present in the first file, for example, the order of sections in the output file will match the order in the first input file. The most frequently used statement in the SECTIONS command is the section definition which specifies the properties of an output section its location, alignment, contents, fill pattern, and target memory region Most of these specifications are optional the simplest form of a section definition is. secname is the name of the output section, and contents a specification of what goes there--for example, a list of input files or sections of input files see section Section Placement As you might assume, the whitespace shown is optional You do need the colon and the braces however. secname must meet the constraints of your output format I n formats which only support a limited number of sections, such as the name must be one of the names supported by the format for example, allows only data or If the output format supports any number of sections, but with numbers and not names as is the case for Oasys , the name should be supplied as a quoted numeric string A section name may consist of any sequence of characters, but any name which does not conform to the standard ld symbol name syntax must be quoted See section Symbol Names. The linker will not create output sections which do not have any contents This is for convenience when referring to input sections that may or may not exist For example. will only create a section in the output file if there is a section in at least one input file. In a section definition, you can specify the contents of an output section by listing particular input files, by listing particular input-file sections, or by a combination of the two You can also place arbitrary data in the section, and d efine symbols relative to the beginning of the section. The contents of a section definition may include any of the following kinds of statement You can include as many of these as you like in a single section definition, separated from one another by whitespace. filename You may simply name a particular input file to be placed in the current output section all sections from that file are placed in the current section definition If the file name has already been mentioned in another section definition, with an explicit section name list, then only those sections which have not yet been allocated are used To specify a list of particular files by name The example also illustrates that multiple statements can be included in the contents of a section definition, since each file name is a separate statement filename section filename section section filename section section You can name one or more sections from your input files, for insertion in the current output section If you wish to speci fy a list of input-file sections inside the parentheses, you may separate the section names by either commas or whitespace section section section section section Instead of explicitly naming particular input files in a link control script, you can refer to all files from the ld command line use instead of a particular file name before the parenthesized input-file section list If you have already explicitly included some files by name, refers to all remaining files--those whose places in the output file have not yet been defined For example, to copy sections 1 through 4 from an Oasys file into the section of an file, and sections 13 and 14 into the section section used to be accepted as an alternate way to specify named sections from all unallocated input files Because some operating systems VMS allow brackets in file names, that notation is no longer supported filename COMMON COMMON Specify where in your output file to place uninitialized data with this notation COMMON by itself refer s to all uninitialized data from all input files so far as it is not yet allocated filename COMMON refers to uninitialized data from a particular file Both are special cases of the general mechanisms for specifying where to place input-file sections ld permits you to refer to uninitialized data as if it were in an input-file section named COMMON regardless of the input file s format. For example, the following command script arranges the output file into three consecutive sections, named data and taking the input for each from the correspondingly named sections of all the input files. The following example reads all of the sections from file all o and places them at the start of output section outputa which starts at location 0x10000 All of section from file foo o follows immediately, in the same output section All of section from foo o goes into output section outputb followed by section from foo1 o All of the remaining and sections from any files are written to output section outputc. The foregoing statements arrange, in your output file, data originating from your input files You can also place data directly in an output section from the link command script Most of these additional statements involve expressions see section Expressions Although these statements are shown separately here for ease of presentation, no such segregation is needed within a section definition in the SECTIONS command you can intermix them freely with any of the statements we ve just described. CREATEOBJECTSYMBOLS Create a symbol for each input file in the current section, set to the address of the first byte of data written from that input file For instance, with files it is conventional to have a symbol for each input file You can accomplish this by defining the output section as follows If is a file containing this script, and a o b o c o and d o are four input files with contents like the following--- ld - M - T a o b o c o d o would create a map like this, containing symbols matching the object file names symbol expression symbol f expression symbol is any symbol name see section Symbol Names f refers to any of the operators - which combine arithmetic and assignment When you assign a value to a symbol within a particular section definition, the value is relative to the beginning of the section see section Assignment Defining Symbols If you write abs and rel do not have the same value rel has the same value as abs2 BYTE expression SHORT expression LONG expression QUAD expression By including one of these four statements in a section definition, you can explicitly place one, two, four, or eight bytes respectively at the current address of that section QUAD is only supported when using a 64 bit host or target Multiple-byte quantities are represented in whatever byte order is appropriate for the output file format see section BFD FILL expression Specify the fill pattern for the current section Any otherwise unspecified regions of memory within the section for example, re gions you skip over by assigning a new value to the location counter are filled with the two least significant bytes from the expression argument A FILL statement covers memory locations after the point it occurs in the section definition by including more than one FILL statement, you can have different fill patterns in different parts of an output section. Here is the full syntax of a section definition, including all the optional portions. secname and contents are required See section Section Definitions and see section Section Placement for details on contents The remaining elements--- start BLOCK align NOLOAD AT ldadr region and fill ---are all optional. start You can force the output section to be loaded at a specified address by specifying start immediately following the section name start can be represented as any expression The following example generates section output at location 0x40000000 BLOCK align You can include BLOCK specification to advance the location counter prior to the beginning of the section, so that the section will begin at the specified alignment align is an expression NOLOAD Use NOLOAD to prevent a section from being loaded into memory each time it is accessed For example, in the script sample below, the ROM segment is addressed at memory location 0 and does not need to be loaded into each object file AT ldadr The expression ldadr that follows the AT keyword specifies the load address of the section The default if you do not use the AT keyword is to make the load address the same as the relocation address This feature is designed to make it easy to build a ROM image For example, this SECTIONS definition creates two output sections one called which starts at 0x1000 and one called which is loaded at the end of the section even though its relocation address is 0x2000 The symbol data is defined with the value 0x2000 The run-time initialization code for C programs, usually crt0 for use with a ROM generated this way has to include something like the following, to copy the initialized data from the ROM image to its runtime address region Assign this section to a previously defined region of memory See section Memory Layout fill Including fill in a section definition specifies the initial fill value for that section You may use any expression to specify fill Any unallocated holes in the current output section when written to the output file will be filled with the two least significant bytes of the value, repeated as necessary You can also change the fill value with a FILL statement in the contents of a section definition. The linker command language includes a command specifically for defining the first executable instruction in an output file its entry point Its argument is a symbol name. Like symbol assignments, the ENTRY command may be placed either as an independent command in the command file, or among the section definitions within the SECTIONS command--whatever makes the most sense for your layout. ENTRY is only one of seve ral ways of choosing the entry point You may indicate it in any of the following ways shown in descending order of priority methods higher in the list override methods lower down. the - e entry command-line option. the ENTRY symbol command in a linker control script. the value of the symbol start if present. the address of the first byte of the section, if present. The address 0.For example, you can use these rules to generate an entry point with an assignment statement if no symbol start is defined within your input files, you can simply define it, assigning it an appropriate value. The example shows an absolute address, but you can use any expression For example, if your input object files use some other symbol-name convention for the entry point, you can just assign the value of whatever symbol contains the start address to start. The command language includes a number of other commands that you can use for specialized purposes They are similar in purpose to command-line options. CONSTRUCTOR S This command ties up C style constructor and destructor records The details of the constructor representation vary from one object format to another, but usually lists of constructors and destructors appear as special sections The CONSTRUCTORS command specifies where the linker is to place the data from these sections, relative to the rest of the linked output Constructor data is marked by the symbol CTORLIST at the start, and CTORLISTEND at the end destructor data is bracketed similarly, between DTORLIST and DTORLISTEND The compiler must arrange to actually run this code GNU C calls constructors from a subroutine main which it inserts automatically into the startup code for main and destructors from exit FLOAT NOFLOAT These keywords were used in some older linkers to request a particular math subroutine library ld doesn t use the keywords, assuming instead that any necessary subroutines are in libraries specified using the general mechanisms for linking to archives but to permit the use of scripts that were written for the older linkers, the keywords FLOAT and NOFLOAT are accepted and ignored FORCECOMMONALLOCATION This command has the same effect as the - d command-line option to make ld assign space to common symbols even if a relocatable output file is specified - r INPUT file file INPUT file file Use this command to include binary input files in the link, without including them in a particular section definition Specify the full name for each file including a if required ld searches for each file through the archive-library search path, just as for files you specify on the command line See the description of - L in xref If you use - l file ld will transform the name to lib file a as with the command line argument - l GROUP file file GROUP file file This command is like INPUT except that the named files should all be archives, and they are searched repeatedly until no new undefined references are created See the description of - in xref OUTPUT filename Use this comm and to name the link output file filename The effect of OUTPUT filename is identical to the effect of - o filename which overrides it You can use this command to supply a default output-file name other than OUTPUTARCH bfdname Specify a particular output machine architecture, with one of the names used by the BFD back-end routines see section BFD This command is often unnecessary the architecture is most often set implicitly by either the system BFD configuration or as a side effect of the OUTPUTFORMAT command OUTPUTFORMAT bfdname When ld is configured to support multiple object code formats, you can use this command to specify a particular output format bfdname is one of the names used by the BFD back-end routines see section BFD The effect is identical to the effect of the - oformat command-line option This selection affects only the output file the related command TARGET affects primarily input files SEARCHDIR path Add path to the list of paths where ld looks for archive libraries SEAR CHDIR path has the same effect as - L path on the command line STARTUP filename Ensure that filename is the first input file used in the link process TARGET format When ld is configured to support multiple object code formats, you can use this command to change the input-file object code format like the command-line option - b or its synonym - format The argument format is one of the strings used by BFD to name binary formats If TARGET is specified but OUTPUTFORMAT is not, the last TARGET argument is also used as the default format for the ld output file See section BFD If you don t use the TARGET command, ld uses the value of the environment variable GNUTARGET if available, to select the output file format If that variable is also absent, ld uses the default format configured for your machine in the BFD libraries Go to the first previous next last section, table of contents. Table of Contents. Copyright C 1991, 92, 93, 94, 95, 96, 97, 1998 Free Software Foundation, Inc. Permission is grante d to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions. ld combines a number of object and archive files, relocates their data and ties up symbol references Usually the last step in compiling a program is to run ld. ld accepts Linker Command Language files written in a superset of AT T s Link Editor Command Language syntax, to provide explicit and total control over the linking process. This version of ld uses the general purpose BFD libraries to operate on object files This allows ld to read, combine, and write obje ct files in many different formats--for example, COFF or Different formats may be linked together to produce any available kind of object file See section BFD for more information. Aside from its flexibility, the GNU linker is more helpful than other linkers in providing diagnostic information Many linkers abandon execution immediately upon encountering an error whenever possible, ld continues executing, allowing you to identify other errors or, in some cases, to get an output file in spite of the error. The GNU linker ld is meant to cover a broad range of situations, and to be as compatible as possible with other linkers As a result, you have many choices to control its behavior. The linker supports a plethora of command-line options, but in actual practice few of them are used in any particular context For instance, a frequent use of ld is to link standard Unix object files on a standard, supported Unix system On such a system, to link a file hello o. This tells ld to produce a file call ed output as the result of linking the file lib crt0 o with hello o and the library libc a which will come from the standard search directories See the discussion of the - l option below. The command-line options to ld may be specified in any order, and may be repeated at will Repeating most options with a different argument will either have no further effect, or override prior occurrences those further to the left on the command line of that option Options which may be meaningfully specified more than once are noted in the descriptions below. Non-option arguments are objects files which are to be linked together They may follow, precede, or be mixed in with command-line options, except that an object file argument may not be placed between an option and its argument. Usually the linker is invoked with at least one object file, but you can specify other forms of binary input files using - l - R and the script command language If no binary input files at all are specified, the linker does not produce any output, and issues the message No input files. If the linker can not recognize the format of an object file, it will assume that it is a linker script A script specified in this way augments the main linker script used for the link either the default linker script or the one specified by using - T This feature permits the linker to link against a file which appears to be an object or an archive, but actually merely defines some symbol values, or uses INPUT or GROUP to load other objects Note that specifying a script in this way should only be used to augment the main linker script if you want to use some command that logically can only appear once, such as the SECTIONS or MEMORY command, you must replace the default linker script using the - T option See section Command Language. For options whose names are a single letter, option arguments must either follow the option letter without intervening whitespace, or be given as separate arguments immediately following the option th at requires them. For options whose names are multiple letters, either one dash or two can precede the option name for example, --oformat and --oformat are equivalent Arguments to multiple-letter options must either be separated from the option name by an equals sign, or be given as separate arguments immediately following the option that requires them For example, --oformat srec and --oformat srec are equivalent Unique abbreviations of the names of multiple-letter options are accepted.-a keyword This option is supported for HP UX compatibility The keyword argument must be one of the strings archive shared or default - aarchive is functionally equivalent to - Bstatic and the other two keywords are functionally equivalent to - Bdynamic This option may be used any number of times - A architecture --architecture architecture In the current release of ld this option is useful only for the Intel 960 family of architectures In that ld configuration, the architecture argument identifies the partic ular architecture in the 960 family, enabling some safeguards and modifying the archive-library search path See section ld and the Intel 960 family for details Future releases of ld may support similar functionality for other architecture families - b input-format --format input-format ld may be configured to support more than one kind of object file If your ld is configured this way, you can use the - b option to specify the binary format for input object files that follow this option on the command line Even when ld is configured to support alternative object formats, you don t usually need to specify this, as ld should be configured to expect as a default input format the most usual format on each machine input-format is a text string, the name of a particular format supported by the BFD libraries You can list the available binary formats with objdump - i See section BFD You may want to use this option if you are linking files with an unusual binary format You can also use - b to switch formats explicitly when linking object files of different formats , by including - b input-format before each group of object files in a particular format The default format is taken from the environment variable GNUTARGET See section Environment Variables You can also define the input format from a script, using the command TARGET see section Option Commands - c MRI-commandfile --mri-script MRI-commandfile For compatibility with linkers produced by MRI, ld accepts script files written in an alternate, restricted command language, described in section MRI Compatible Script Files Introduce MRI script files with the option - c use the - T option to run linker scripts written in the general-purpose ld scripting language If MRI-cmdfile does not exist, ld looks for it in the directories specified by any - L options - d - dc - dp These three options are equivalent multiple forms are supported for compatibility with other linkers They assign space to common symbols even if a relocatable output fil e is specified with - r The script command FORCECOMMONALLOCATION has the same effect See section Option Commands - e entry --entry entry Use entry as the explicit symbol for beginning execution of your program, rather than the default entry point See section The Entry Point for a discussion of defaults and other ways of specifying the entry point - E --export-dynamic When creating a dynamically linked executable, add all symbols to the dynamic symbol table The dynamic symbol table is the set of symbols which are visible from dynamic objects at run time If you do not use this option, the dynamic symbol table will normally contain only those symbols which are referenced by some dynamic object mentioned in the link If you use dlopen to load a dynamic object which needs to refer back to the symbols defined by the program, rather than some other dynamic object, then you will probably need to use this option when linking the program itself - f --auxiliary name When creating an ELF shared object, set the internal DTAUXILIARY field to the specified name This tells the dynamic linker that the symbol table of the shared object should be used as an auxiliary filter on the symbol table of the shared object name If you later link a program against this filter object, then, when you run the program, the dynamic linker will see the DTAUXILIARY field If the dynamic linker resolves any symbols from the filter object, it will first check whether there is a definition in the shared object name If there is one, it will be used instead of the definition in the filter object The shared object name need not exist Thus the shared object name may be used to provide an alternative implementation of certain functions, perhaps for debugging or for machine specific performance This option may be specified more than once The DTAUXILIARY entries will be created in the order in which they appear on the command line - F name --filter name When creating an ELF shared object, set the internal DTFILTER fie ld to the specified name This tells the dynamic linker that the symbol table of the shared object which is being created should be used as a filter on the symbol table of the shared object name If you later link a program against this filter object, then, when you run the program, the dynamic linker will see the DTFILTER field The dynamic linker will resolve symbols according to the symbol table of the filter object as usual, but it will actually link to the definitions found in the shared object name Thus the filter object can be used to select a subset of the symbols provided by the object name Some older linkers used the - F option throughout a compilation toolchain for specifying object-file format for both input and output object files The GNU linker uses other mechanisms for this purpose the - b --format --oformat options, the TARGET command in linker scripts, and the GNUTARGET environment variable The GNU linker will ignore the - F option when not creating an ELF shared object --fo rce-exe-suffix Make sure that an output file has a suffix If a successfully built fully linked output file does not have a or suffix, this option forces the linker to copy the output file to one of the same name with a suffix This option is useful when using unmodified Unix makefiles on a Microsoft Windows host, since some versions of Windows won t run an image unless it ends in a suffix - g Ignored Provided for compatibility with other tools - G value --gpsize value Set the maximum size of objects to be optimized using the GP register to size This is only meaningful for object file formats such as MIPS ECOFF which supports putting large and small objects into different sections This is ignored for other object file formats - h name - soname name When creating an ELF shared object, set the internal DTSONAME field to the specified name When an executable is linked with a shared object which has a DTSONAME field, then when the executable is run the dynamic linker will attempt to load the sha red object specified by the DTSONAME field rather than the using the file name given to the linker - i Perform an incremental link same as option - r - l archive --library archive Add archive file archive to the list of files to link This option may be used any number of times ld will search its path-list for occurrences of lib archive a for every archive specified On systems which support shared libraries, ld may also search for libraries with extensions other than a Specifically, on ELF and SunOS systems, ld will search a directory for a library with an extension of before searching for one with an extension of a By convention, a extension indicates a shared library The linker will search an archive only once, at the location where it is specified on the command line If the archive defines a symbol which was undefined in some object which appeared before the archive on the command line, the linker will include the appropriate file s from the archive However, an undefined symbol in an ob ject appearing later on the command line will not cause the linker to search the archive again See the - option for a way to force the linker to search archives multiple times You may list the same archive multiple times on the command line This type of archive searching is standard for Unix linkers However, if you are using ld on AIX, note that it is different from the behaviour of the AIX linker - L searchdir --library-path searchdir Add path searchdir to the list of paths that ld will search for archive libraries and ld control scripts You may use this option any number of times The directories are searched in the order in which they are specified on the command line Directories specified on the command line are searched before the default directories All - L options apply to all - l options, regardless of the order in which the options appear The default set of paths searched without being specified with - L depends on which emulation mode ld is using, and in some cases also on how it was configured See section Environment Variables The paths can also be specified in a link script with the SEARCHDIR command Directories specified this way are searched at the point in which the linker script appears in the command line - m emulation Emulate the emulation linker You can list the available emulations with the --verbose or - V options If the - m option is not used, the emulation is taken from the LDEMULATION environment variable, if that is defined Otherwise, the default emulation depends upon how the linker was configured - M --print-map Print a link map to the standard output A link map provides information about the link, including the following. Where object files and symbols are mapped into memory. How common symbols are allocated. All archive members included in the link, with a mention of the symbol which caused the archive member to be brought in.-n --nmagic Set the text segment to be read only, and mark the output as NMAGIC if possible - N --omagic Set the text and data sections to be readable and writable Also, do not page-align the data segment If the output format supports Unix style magic numbers, mark the output as OMAGIC - o output --output output Use output as the name for the program produced by ld if this option is not specified, the name is used by default The script command OUTPUT can also specify the output file name - r --relocateable Generate relocatable output--i e generate an output file that can in turn serve as input to ld This is often called partial linking As a side effect, in environments that support standard Unix magic numbers, this option also sets the output file s magic number to OMAGIC If this option is not specified, an absolute file is produced When linking C programs, this option will not resolve references to constructors to do that, use - Ur This option does the same thing as - i - R filename --just-symbols filename Read symbol names and their addresses from filename but do not relocate it or include it in the output This allows your output file to refer symbolically to absolute locations of memory defined in other programs You may use this option more than once For compatibility with other ELF linkers, if the - R option is followed by a directory name, rather than a file name, it is treated as the - rpath option - s --strip-all Omit all symbol information from the output file - S --strip-debug Omit debugger symbol information but not all symbols from the output file - t --trace Print the names of the input files as ld processes them - T commandfile --script commandfile Read link commands from the file commandfile These commands replace ld s default link script rather than adding to it , so commandfile must specify everything necessary to describe the target format You must use this option if you want to use a command which can only appear once in a linker script, such as the SECTIONS or MEMORY command See section Command Language If commandfile does not exist, ld looks for it in the directories specified by any preceding - L options Multiple - T options accumulate - u symbol --undefined symbol Force symbol to be entered in the output file as an undefined symbol Doing this may, for example, trigger linking of additional modules from standard libraries - u may be repeated with different option arguments to enter additional undefined symbols - v --version - V Display the version number for ld The - V option also lists the supported emulations - x --discard-all Delete all local symbols - X --discard-locals Delete all temporary local symbols For most targets, this is all local symbols whose names begin with L - y symbol --trace-symbol symbol Print the name of each linked file in which symbol appears This option may be given any number of times On many systems it is necessary to prepend an underscore This option is useful when you have an undefined symbol in your link but don t know where the reference is coming from - Y path Add path to the default library search path This option exists for Solaris comp atibility - z keyword This option is ignored for Solaris compatibility - archives - --start-group archives --end-group The archives should be a list of archive files They may be either explicit file names, or - l options The specified archives are searched repeatedly until no new undefined references are created Normally, an archive is searched only once in the order that it is specified on the command line If a symbol in that archive is needed to resolve an undefined symbol referred to by an object in an archive that appears later on the command line, the linker would not be able to resolve that reference By grouping the archives, they all be searched repeatedly until all possible references are resolved Using this option has a significant performance cost It is best to use it only when there are unavoidable circular references between two or more archives - assert keyword This option is ignored for SunOS compatibility - Bdynamic - dy - callshared Link against dynamic libraries This is only meaningful on platforms for which shared libraries are supported This option is normally the default on such platforms The different variants of this option are for compatibility with various systems You may use this option multiple times on the command line it affects library searching for - l options which follow it - Bstatic - dn - nonshared - static Do not link against shared libraries This is only meaningful on platforms for which shared libraries are supported The different variants of this option are for compatibility with various systems You may use this option multiple times on the command line it affects library searching for - l options which follow it - Bsymbolic When creating a shared library, bind references to global symbols to the definition within the shared library, if any Normally, it is possible for a program linked against a shared library to override the definition within the shared library This option is only meaningful on ELF platforms which support shared libraries - - cref Output a cross reference table If a linker map file is being generated, the cross reference table is printed to the map file Otherwise, it is printed on the standard output The format of the table is intentionally simple, so that it may be easily processed by a script if necessary The symbols are printed out, sorted by name For each symbol, a list of file names is given If the symbol is defined, the first file listed is the location of the definition The remaining files contain references to the symbol --defsym symbol expression Create a global symbol in the output file, containing the absolute address given by expression You may use this option as many times as necessary to define multiple symbols in the command line A limited form of arithmetic is supported for the expression in this context you may give a hexadecimal constant or the name of an existing symbol, or use and - to add or subtract hexadecimal constants or symbols If you need more elaborate expressions, consider usin g the linker command language from a script see section Assignment Defining Symbols Note there should be no white space between symbol the equals sign , and expression --dynamic-linker file Set the name of the dynamic linker This is only meaningful when generating dynamically linked ELF executables The default dynamic linker is normally correct don t use this unless you know what you are doing - EB Link big-endian objects This affects the default output format - EL Link little-endian objects This affects the default output format --embedded-relocs This option is only meaningful when linking MIPS embedded PIC code, generated by the - membedded-pic option to the GNU compiler and assembler It causes the linker to create a table which may be used at runtime to relocate any data which was statically initialized to pointer values See the code in testsuite ld-empic for details --help Print a summary of the command-line options on the standard output and exit - Map mapfile Print a link map to the file mapfile See the description of the - M option, above --no-keep-memory ld normally optimizes for speed over memory usage by caching the symbol tables of input files in memory This option tells ld to instead optimize for memory usage, by rereading the symbol tables as necessary This may be required if ld runs out of memory space while linking a large executable --no-warn-mismatch Normally ld will give an error if you try to link together input files that are mismatched for some reason, perhaps because they have been compiled for different processors or for different endiannesses This option tells ld that it should silently permit such possible errors This option should only be used with care, in cases when you have taken some special action that ensures that the linker errors are inappropriate --no-whole-archive Turn off the effect of the --whole-archive option for subsequent archive files --noinhibit-exec Retain the executable output file whenever it is still usable Normally, the li nker will not produce an output file if it encounters errors during the link process it exits without writing an output file when it issues any error whatsoever --oformat output-format ld may be configured to support more than one kind of object file If your ld is configured this way, you can use the --oformat option to specify the binary format for the output object file Even when ld is configured to support alternative object formats, you don t usually need to specify this, as ld should be configured to produce as a default output format the most usual format on each machine output-format is a text string, the name of a particular format supported by the BFD libraries You can list the available binary formats with objdump - i The script command OUTPUTFORMAT can also specify the output format, but this option overrides it See section BFD - qmagic This option is ignored for Linux compatibility - Qy This option is ignored for SVR4 compatibility --relax An option with machine dependent effe cts This option is only supported on a few targets See section ld and the H8 300 See section ld and the Intel 960 family On some platforms, the --relax option performs global optimizations that become possible when the linker resolves addressing in the program, such as relaxing address modes and synthesizing new instructions in the output object file On platforms where this is not supported, --relax is accepted, but ignored --retain-symbols-file filename Retain only the symbols listed in the file filename discarding all others filename is simply a flat file, with one symbol name per line This option is especially useful in environments such as VxWorks where a large global symbol table is accumulated gradually, to conserve run-time memory --retain-symbols-file does not discard undefined symbols, or symbols needed for relocations You may only specify --retain-symbols-file once in the command line It overrides - s and - S - rpath dir Add a directory to the runtime library search path This is used when linking an ELF executable with shared objects All - rpath arguments are concatenated and passed to the runtime linker, which uses them to locate shared objects at runtime The - rpath option is also used when locating shared objects which are needed by shared objects explicitly included in the link see the description of the - rpath-link option If - rpath is not used when linking an ELF executable, the contents of the environment variable LDRUNPATH will be used if it is defined The - rpath option may also be used on SunOS By default, on SunOS, the linker will form a runtime search patch out of all the - L options it is given If a - rpath option is used, the runtime search path will be formed exclusively using the - rpath options, ignoring the - L options This can be useful when using gcc, which adds many - L options which may be on NFS mounted filesystems For compatibility with other ELF linkers, if the - R option is followed by a directory name, rather than a file name, it is treated a s the - rpath option - rpath-link DIR When using ELF or SunOS, one shared library may require another This happens when an ld - shared link includes a shared library as one of the input files When the linker encounters such a dependency when doing a non-shared, non-relocateable link, it will automatically try to locate the required shared library and include it in the link, if it is not included explicitly In such a case, the - rpath-link option specifies the first set of directories to search The - rpath-link option may specify a sequence of directory names either by specifying a list of names separated by colons, or by appearing multiple times The linker uses the following search paths to locate required shared libraries. Any directories specified by - rpath-link options. Any directories specified by - rpath options The difference between - rpath and - rpath-link is that directories specified by - rpath options are included in the executable and used at runtime, whereas the - rpath-link option is only effective at link time. On an ELF system, if the - rpath and rpath-link options were not used, search the contents of the environment variable LDRUNPATH. On SunOS, if the - rpath option was not used, search any directories specified using - L options. For a native linker, the contents of the environment variable LDLIBRARYPATH. The default directories, normally lib and usr lib. If the required shared library is not found, the linker will issue a warning and continue with the link - shared - Bshareable Create a shared library This is currently only supported on ELF, XCOFF and SunOS platforms On SunOS, the linker will automatically create a shared library if the - e option is not used and there are undefined symbols in the link --sort-common This option tells ld to sort the common symbols by size when it places them in the appropriate output sections First come all the one byte symbols, then all the two bytes, then all the four bytes, and then everything else This is to prevent gaps between sy mbols due to alignment constraints --split-by-file Similar to --split-by-reloc but creates a new output section for each input file --split-by-reloc count Trys to creates extra sections in the output file so that no single output section in the file contains more than count relocations This is useful when generating huge relocatable for downloading into certain real time kernels with the COFF object file format since COFF cannot represent more than 65535 relocations in a single section Note that this will fail to work with object file formats which do not support arbitrary sections The linker will not split up individual input sections for redistribution, so if a single input section contains more than count relocations one output section will contain that many relocations --stats Compute and display statistics about the operation of the linker, such as execution time and memory usage --traditional-format For some targets, the output of ld is different in some ways from the output of s ome existing linker This switch requests ld to use the traditional format instead For example, on SunOS, ld combines duplicate entries in the symbol string table This can reduce the size of an output file with full debugging information by over 30 percent Unfortunately, the SunOS dbx program can not read the resulting program gdb has no trouble The --traditional-format switch tells ld to not combine duplicate entries - Tbss org - Tdata org - Ttext org Use org as the starting address for--respectively--the bss data or the text segment of the output file org must be a single hexadecimal integer for compatibility with other linkers, you may omit the leading 0x usually associated with hexadecimal values - Ur For anything other than C programs, this option is equivalent to - r it generates relocatable output--i e an output file that can in turn serve as input to ld When linking C programs, - Ur does resolve references to constructors, unlike - r It does not work to use - Ur on files that were thems elves linked with - Ur once the constructor table has been built, it cannot be added to Use - Ur only for the last partial link, and - r for the others --verbose Display the version number for ld and list the linker emulations supported Display which input files can and cannot be opened Display the linker script if using a default builtin script --version-script version-scriptfile Specify the name of a version script to the linker This is typically used when creating shared libraries to specify additional information about the version heirarchy for the library being created This option is only meaningful on ELF platforms which support shared libraries See section Version Script --warn-common Warn when a common symbol is combined with another common symbol or with a symbol definition Unix linkers allow this somewhat sloppy practice, but linkers on some other operating systems do not This option allows you to find potential problems from combining global symbols Unfortunately, some C libra ries use this practice, so you may get some warnings about symbols in the libraries as well as in your programs There are three kinds of global symbols, illustrated here by C examples int i 1 A definition, which goes in the initialized data section of the output file extern int i An undefined reference, which does not allocate space There must be either a definition or a common symbol for the variable somewhere int i A common symbol If there are only one or more common symbols for a variable, it goes in the uninitialized data area of the output file The linker merges multiple common symbols for the same variable into a single symbol If they are of different sizes, it picks the largest size The linker turns a common symbol into a declaration, if there is a definition of the same variable The --warn-common option can produce five kinds of warnings Each warning consists of a pair of lines the first describes the symbol just encountered, and the second describes the previous symbol encount ered with the same name One or both of the two symbols will be a common symbol. Turning a common symbol into a reference, because there is already a definition for the symbol. Turning a common symbol into a reference, because a later definition for the symbol is encountered This is the same as the previous case, except that the symbols are encountered in a different order. Merging a common symbol with a previous same-sized common symbol. Merging a common symbol with a previous larger common symbol. Merging a common symbol with a previous smaller common symbol This is the same as the previous case, except that the symbols are encountered in a different order.--warn-constructors Warn if any global constructors are used This is only useful for a few object file formats For formats like COFF or ELF, the linker can not detect the use of global constructors --warn-multiple-gp Warn if multiple global pointer values are required in the output file This is only meaningful for certain processors, suc h as the Alpha Specifically, some processors put large-valued constants in a special section A special register the global pointer points into the middle of this section, so that constants can be loaded efficiently via a base-register relative addressing mode Since the offset in base-register relative mode is fixed and relatively small e g 16 bits , this limits the maximum size of the constant pool Thus, in large programs, it is often necessary to use multiple global pointer values in order to be able to address all possible constants This option causes a warning to be issued whenever this case occurs --warn-once Only warn once for each undefined symbol, rather than once per module which refers to it --warn-section-align Warn if the address of an output section is changed because of alignment Typically, the alignment will be set by an input section The address will only be changed if it not explicitly specified that is, if the SECTIONS command does not specify a start address for the s ection see section Specifying Output Sections --whole-archive For each archive mentioned on the command line after the --whole-archive option, include every object file in the archive in the link, rather than searching the archive for the required object files This is normally used to turn an archive file into a shared library, forcing every object to be included in the resulting shared library This option may be used more than once --wrap symbol Use a wrapper function for symbol Any undefined reference to symbol will be resolved to wrap symbol Any undefined reference to real symbol will be resolved to symbol This can be used to provide a wrapper for a system function The wrapper function should be called wrap symbol If it wishes to call the system function, it should call real symbol Here is a trivial example If you link other code with this file using --wrap malloc then all calls to malloc will call the function wrapmalloc instead The call to realmalloc in wrapmalloc will call the re al malloc function You may wish to provide a realmalloc function as well, so that links without the --wrap option will succeed If you do this, you should not put the definition of realmalloc in the same file as wrapmalloc if you do, the assembler may resolve the call before the linker has a chance to wrap it to malloc. You can change the behavior of ld with the environment variables GNUTARGET and LDEMULATION. GNUTARGET determines the input-file object format if you don t use - b or its synonym --format Its value should be one of the BFD names for an input format see section BFD If there is no GNUTARGET in the environment, ld uses the natural format of the target If GNUTARGET is set to default then BFD attempts to discover the input format by examining binary input files this method often succeeds, but there are potential ambiguities, since there is no method of ensuring that the magic number used to specify object-file formats is unique However, the configuration procedure for BFD on eac h system places the conventional format for that system first in the search-list, so ambiguities are resolved in favor of convention. LDEMULATION determines the default emulation if you don t use the - m option The emulation can affect various aspects of linker behaviour, particularly the default linker script You can list the available emulations with the --verbose or - V options If the - m option is not used, and the LDEMULATION environment variable is not defined, the default emulation depends upon how the linker was configured. The command language provides explicit control over the link process, allowing complete specification of the mapping between the linker s input files and its output It controls. input files. file formats. output file layout. addresses of sections. placement of common blocks. You may supply a command file also known as a linker script to the linker either explicitly through the - T option, or implicitly as an ordinary file Normally you should use the - T option An implici t linker script should only be used when you want to augment, rather than replace, the default linker script typically an implicit linker script would consist only of INPUT or GROUP commands. If the linker opens a file which it cannot recognize as a supported object or archive format, nor as a linker script, it reports an error.2 1 Command Line Options. The linker supports a plethora of command-line options, but in actual practice few of them are used in any particular context For instance, a frequent use of ld is to link standard Unix object files on a standard, supported Unix system On such a system, to link a file hello o. This tells ld to produce a file called output as the result of linking the file lib crt0 o with hello o and the library libc a which will come from the standard search directories See the discussion of the - l option below. Some of the command-line options to ld may be specified at any point in the command line However, options which refer to files, such as - l or - T , cause the file to be read at the point at which the option appears in the command line, relative to the object files and other file options Repeating non-file options with a different argument will either have no further effect, or override prior occurrences those further to the left on the command line of that option Options which may be meaningfully specified more than once are noted in the descriptions below. Non-option arguments are object files or archives which are to be linked together They may follow, precede, or be mixed in with command-line options, except that an object file argument may not be placed between an option and its argument. Usually the linker is invoked with at least one object file, but you can specify other forms of binary input files using - l , - R , and the script command language If no binary input files at all are specified, the linker does not produce any output, and issues the message No input files. If the linker cannot recognize the format of an object fil e, it will assume that it is a linker script A script specified in this way augments the main linker script used for the link either the default linker script or the one specified by using - T This feature permits the linker to link against a file which appears to be an object or an archive, but actually merely defines some symbol values, or uses INPUT or GROUP to load other objects Specifying a script in this way merely augments the main linker script, with the extra commands placed after the main script use the - T option to replace the default linker script entirely, but note the effect of the INSERT command See Scripts. For options whose names are a single letter, option arguments must either follow the option letter without intervening whitespace, or be given as separate arguments immediately following the option that requires them. For options whose names are multiple letters, either one dash or two can precede the option name for example, - trace-symbol and --trace-symbol are equival ent Note there is one exception to this rule Multiple letter options that start with a lower case o can only be preceded by two dashes This is to reduce confusion with the - o option So for example - omagic sets the output file name to magic whereas --omagic sets the NMAGIC flag on the output. Arguments to multiple-letter options must either be separated from the option name by an equals sign, or be given as separate arguments immediately following the option that requires them For example, --trace-symbol foo and --trace-symbol foo are equivalent Unique abbreviations of the names of multiple-letter options are accepted. Note if the linker is being invoked indirectly, via a compiler driver e g gcc then all the linker command line options should be prefixed by - Wl, or whatever is appropriate for the particular compiler driver like this. This is important, because otherwise the compiler driver program may silently drop the linker options, resulting in a bad link Confusion may also arise when p assing options that require values through a driver, as the use of a space between option and argument acts as a separator, and causes the driver to pass only the option to the linker and the argument to the compiler In this case, it is simplest to use the joined forms of both single - and multiple-letter options, such as. Here is a table of the generic command line switches accepted by the GNU linker file Read command-line options from file The options read are inserted in place of the original file option If file does not exist, or cannot be read, then the option will be treated literally, and not removed. Options in file are separated by whitespace A whitespace character may be included in an option by surrounding the entire option in either single or double quotes Any character including a backslash may be included by prefixing the character to be included with a backslash The file may itself contain additional file options any such options will be processed recursively.-a keyword Thi s option is supported for HP UX compatibility The keyword argument must be one of the strings archive , shared , or default - aarchive is functionally equivalent to - Bstatic , and the other two keywords are functionally equivalent to - Bdynamic This option may be used any number of times.--audit AUDITLIB Adds AUDITLIB to the DTAUDIT entry of the dynamic section AUDITLIB is not checked for existence, nor will it use the DTSONAME specified in the library If specified multiple times DTAUDIT will contain a colon separated list of audit interfaces to use If the linker finds an object with an audit entry while searching for shared libraries, it will add a corresponding DTDEPAUDIT entry in the output file This option is only meaningful on ELF platforms supporting the rtld-audit interface.-A architecture --architecture architecture In the current release of ld this option is useful only for the Intel 960 family of architectures In that ld configuration, the architecture argument identifies the p articular architecture in the 960 family, enabling some safeguards and modifying the archive-library search path See ld and the Intel 960 family for details. Future releases of ld may support similar functionality for other architecture families.-b input-format --format input-format ld may be configured to support more than one kind of object file If your ld is configured this way, you can use the - b option to specify the binary format for input object files that follow this option on the command line Even when ld is configured to support alternative object formats, you don t usually need to specify this, as ld should be configured to expect as a default input format the most usual format on each machine input-format is a text string, the name of a particular format supported by the BFD libraries You can list the available binary formats with objdump - i See BFD. You may want to use this option if you are linking files with an unusual binary format You can also use - b to switch formats ex plicitly when linking object files of different formats , by including - b input-format before each group of object files in a particular format. The default format is taken from the environment variable GNUTARGET See Environment You can also define the input format from a script, using the command TARGET see Format Commands.-c MRI-commandfile --mri-script MRI-commandfile For compatibility with linkers produced by MRI, ld accepts script files written in an alternate, restricted command language, described in MRI Compatible Script Files Introduce MRI script files with the option - c use the - T option to run linker scripts written in the general-purpose ld scripting language If MRI-cmdfile does not exist, ld looks for it in the directories specified by any - L options.-d - dc - dp These three options are equivalent multiple forms are supported for compatibility with other linkers They assign space to common symbols even if a relocatable output file is specified with - r The script command FOR CECOMMONALLOCATION has the same effect See Miscellaneous Commands.--depaudit AUDITLIB - P AUDITLIB Adds AUDITLIB to the DTDEPAUDIT entry of the dynamic section AUDITLIB is not checked for existence, nor will it use the DTSONAME specified in the library If specified multiple times DTDEPAUDIT will contain a colon separated list of audit interfaces to use This option is only meaningful on ELF platforms supporting the rtld-audit interface The - P option is provided for Solaris compatibility.-e entry --entry entry Use entry as the explicit symbol for beginning execution of your program, rather than the default entry point If there is no symbol named entry the linker will try to parse entry as a number, and use that as the entry address the number will be interpreted in base 10 you may use a leading 0x for base 16, or a leading 0 for base 8 See Entry Point for a discussion of defaults and other ways of specifying the entry point.--exclude-libs lib lib Specifies a list of archive libraries from which symbols should not be automatically exported The library names may be delimited by commas or colons Specifying --exclude-libs ALL excludes symbols in all archive libraries from automatic export This option is available only for the i386 PE targeted port of the linker and for ELF targeted ports For i386 PE, symbols explicitly listed in a file are still exported, regardless of this option For ELF targeted ports, symbols affected by this option will be treated as hidden.--exclude-modules-for-implib module module Specifies a list of object files or archive members, from which symbols should not be automatically exported, but which should be copied wholesale into the import library being generated during the link The module names may be delimited by commas or colons, and must match exactly the filenames used by ld to open the files for archive members, this is simply the member name, but for object files the name listed must include and match precisely any path used to specify the in put file on the linker s command-line This option is available only for the i386 PE targeted port of the linker Symbols explicitly listed in a file are still exported, regardless of this option.-E --export-dynamic --no-export-dynamic When creating a dynamically linked executable, using the - E option or the --export-dynamic option causes the linker to add all symbols to the dynamic symbol table The dynamic symbol table is the set of symbols which are visible from dynamic objects at run time. If you do not use either of these options or use the --no-export-dynamic option to restore the default behavior , the dynamic symbol table will normally contain only those symbols which are referenced by some dynamic object mentioned in the link. If you use dlopen to load a dynamic object which needs to refer back to the symbols defined by the program, rather than some other dynamic object, then you will probably need to use this option when linking the program itself. You can also use the dynamic list to control what symbols should be added to the dynamic symbol table if the output format supports it See the description of --dynamic-list. Note that this option is specific to ELF targeted ports PE targets support a similar function to export all symbols from a DLL or EXE see the description of --export-all-symbols below.-EB Link big-endian objects This affects the default output format.-EL Link little-endian objects This affects the default output format.-f name --auxiliary name When creating an ELF shared object, set the internal DTAUXILIARY field to the specified name This tells the dynamic linker that the symbol table of the shared object should be used as an auxiliary filter on the symbol table of the shared object name. If you later link a program against this filter object, then, when you run the program, the dynamic linker will see the DTAUXILIARY field If the dynamic linker resolves any symbols from the filter object, it will first check whether there is a definition in the sh ared object name If there is one, it will be used instead of the definition in the filter object The shared object name need not exist Thus the shared object name may be used to provide an alternative implementation of certain functions, perhaps for debugging or for machine specific performance. This option may be specified more than once The DTAUXILIARY entries will be created in the order in which they appear on the command line.-F name --filter name When creating an ELF shared object, set the internal DTFILTER field to the specified name This tells the dynamic linker that the symbol table of the shared object which is being created should be used as a filter on the symbol table of the shared object name. If you later link a program against this filter object, then, when you run the program, the dynamic linker will see the DTFILTER field The dynamic linker will resolve symbols according to the symbol table of the filter object as usual, but it will actually link to the definitions foun d in the shared object name Thus the filter object can be used to select a subset of the symbols provided by the object name. Some older linkers used the - F option throughout a compilation toolchain for specifying object-file format for both input and output object files The gnu linker uses other mechanisms for this purpose the - b --format --oformat options, the TARGET command in linker scripts, and the GNUTARGET environment variable The gnu linker will ignore the - F option when not creating an ELF shared object.-fini name When creating an ELF executable or shared object, call NAME when the executable or shared object is unloaded, by setting DTFINI to the address of the function By default, the linker uses fini as the function to call.-g Ignored Provided for compatibility with other tools.-G value --gpsize value Set the maximum size of objects to be optimized using the GP register to size This is only meaningful for object file formats such as MIPS ELF that support putting large and sma ll objects into different sections This is ignored for other object file formats.-h name - soname name When creating an ELF shared object, set the internal DTSONAME field to the specified name When an executable is linked with a shared object which has a DTSONAME field, then when the executable is run the dynamic linker will attempt to load the shared object specified by the DTSONAME field rather than the using the file name given to the linker.-i Perform an incremental link same as option - r.-init name When creating an ELF executable or shared object, call NAME when the executable or shared object is loaded, by setting DTINIT to the address of the function By default, the linker uses init as the function to call.-l namespec --library namespec Add the archive or object file specified by namespec to the list of files to link This option may be used any number of times If namespec is of the form filename ld will search the library path for a file called filename otherwise it will search t he library path for a file called lib namespec a. On systems which support shared libraries, ld may also search for files other than lib namespec a Specifically, on ELF and SunOS systems, ld will search a directory for a library called lib namespec before searching for one called lib namespec a By convention, a extension indicates a shared library Note that this behavior does not apply to filename which always specifies a file called filename. The linker will search an archive only once, at the location where it is specified on the command line If the archive defines a symbol which was undefined in some object which appeared before the archive on the command line, the linker will include the appropriate file s from the archive However, an undefined symbol in an object appearing later on the command line will not cause the linker to search the archive again. See the - option for a way to force the linker to search archives multiple times. You may list the same archive multiple times on the command line. This type of archive searching is standard for Unix linkers However, if you are using ld on AIX, note that it is different from the behaviour of the AIX linker.-L searchdir --library-path searchdir Add path searchdir to the list of paths that ld will search for archive libraries and ld control scripts You may use this option any number of times The directories are searched in the order in which they are specified on the command line Directories specified on the command line are searched before the default directories All - L options apply to all - l options, regardless of the order in which the options appear - L options do not affect how ld searches for a linker script unless - T option is specified. If searchdir begins with then the will be replaced by the sysroot prefix controlled by the --sysroot option, or specified when the linker is configured. The default set of paths searched without being specified with - L depends on which emulation mode ld is using, and in some cases also on how it was configured See Environment. The paths can also be specified in a link script with the SEARCHDIR command Directories specified this way are searched at the point in which the linker script appears in the command line.-m emulation Emulate the emulation linker You can list the available emulations with the --verbose or - V options. If the - m option is not used, the emulation is taken from the LDEMULATION environment variable, if that is defined. Otherwise, the default emulation depends upon how the linker was configured.-M --print-map Print a link map to the standard output A link map provides information about the link, including the following. Where object files are mapped into memory. How common symbols are allocated. All archive members included in the link, with a mention of the symbol which caused the archive member to be brought in. The values assigned to symbols. Note - symbols whose values are computed by an expression which involves a reference to a previous value of t he same symbol may not have correct result displayed in the link map This is because the linker discards intermediate results and only retains the final value of an expression Under such circumstances the linker will display the final value enclosed by square brackets Thus for example a linker script containing. will produce the following output in the link map if the - M option is used. See Expressions for more information about expressions in linker scripts.-n --nmagic Turn off page alignment of sections, and disable linking against shared libraries If the output format supports Unix style magic numbers, mark the output as NMAGIC.-N --omagic Set the text and data sections to be readable and writable Also, do not page-align the data segment, and disable linking against shared libraries If the output format supports Unix style magic numbers, mark the output as OMAGIC Note Although a writable text section is allowed for PE-COFF targets, it does not conform to the format specification publi shed by Microsoft.--no-omagic This option negates most of the effects of the - N option It sets the text section to be read-only, and forces the data segment to be page-aligned Note - this option does not enable linking against shared libraries Use - Bdynamic for this.-o output --output output Use output as the name for the program produced by ld if this option is not specified, the name is used by default The script command OUTPUT can also specify the output file name.-O level If level is a numeric values greater than zero ld optimizes the output This might take significantly longer and therefore probably should only be enabled for the final binary At the moment this option only affects ELF shared library generation Future releases of the linker may make more use of this option Also currently there is no difference in the linker s behaviour for different non-zero values of this option Again this may change with future releases.--push-state The --push-state allows to preserve the curren t state of the flags which govern the input file handling so that they can all be restored with one corresponding --pop-state option. The option which are covered are - Bdynamic - Bstatic - dn - dy - callshared - nonshared - static - N - n --whole-archive --no-whole-archive - r - Ur --copy-dt-needed-entries --no-copy-dt-needed-entries --as-needed --no-as-needed and - a. One target for this option are specifications for pkg-config When used with the --libs option all possibly needed libraries are listed and then possibly linked with all the time It is better to return something as follows. Undoes the effect of push-state, restores the previous values of the flags governing input file handling.-q --emit-relocs Leave relocation sections and contents in fully linked executables Post link analysis and optimization tools may need this information in order to perform correct modifications of executables This results in larger executables. This option is currently only supported on ELF platforms.--force-dynam ic Force the output file to have dynamic sections This option is specific to VxWorks targets.-r --relocatable Generate relocatable output i e generate an output file that can in turn serve as input to ld This is often called partial linking As a side effect, in environments that support standard Unix magic numbers, this option also sets the output file s magic number to OMAGIC If this option is not specified, an absolute file is produced When linking C programs, this option will not resolve references to constructors to do that, use - Ur. When an input file does not have the same format as the output file, partial linking is only supported if that input file does not contain any relocations Different output formats can have further restrictions for example some - based formats do not support partial linking with input files in other formats at all. This option does the same thing as - i.-R filename --just-symbols filename Read symbol names and their addresses from filename but do not reloca te it or include it in the output This allows your output file to refer symbolically to absolute locations of memory defined in other programs You may use this option more than once. For compatibility with other ELF linkers, if the - R option is followed by a directory name, rather than a file name, it is treated as the - rpath option.-s --strip-all Omit all symbol information from the output file.-S --strip-debug Omit debugger symbol information but not all symbols from the output file.-t --trace Print the names of the input files as ld processes them.-T scriptfile --script scriptfile Use scriptfile as the linker script This script replaces ld s default linker script rather than adding to it , so commandfile must specify everything necessary to describe the output file See Scripts If scriptfile does not exist in the current directory, ld looks for it in the directories specified by any preceding - L options Multiple - T options accumulate.-dT scriptfile --default-script scriptfile Use scri ptfile as the default linker script See Scripts. This option is similar to the --script option except that processing of the script is delayed until after the rest of the command line has been processed This allows options placed after the --default-script option on the command line to affect the behaviour of the linker script, which can be important when the linker command line cannot be directly controlled by the user eg because the command line is being constructed by another tool, such as gcc.-u symbol --undefined symbol Force symbol to be entered in the output file as an undefined symbol Doing this may, for example, trigger linking of additional modules from standard libraries - u may be repeated with different option arguments to enter additional undefined symbols This option is equivalent to the EXTERN linker script command. If this option is being used to force additional modules to be pulled into the link, and if it is an error for the symbol to remain undefined, then the option --require-defined should be used instead.--require-defined symbol Require that symbol is defined in the output file This option is the same as option --undefined except that if symbol is not defined in the output file then the linker will issue an error and exit The same effect can be achieved in a linker script by using EXTERN ASSERT and DEFINED together This option can be used multiple times to require additional symbols.-Ur For anything other than C programs, this option is equivalent to - r it generates relocatable output i e an output file that can in turn serve as input to ld When linking C programs, - Ur does resolve references to constructors, unlike - r It does not work to use - Ur on files that were themselves linked with - Ur once the constructor table has been built, it cannot be added to Use - Ur only for the last partial link, and - r for the others.--orphan-handling MODE Control how orphan sections are handled An orphan section is one not specifically mentioned in a linker scr ipt See Orphan Sections. MODE can have any of the following values place Orphan sections are placed into a suitable output section following the strategy described in Orphan Sections The option --unique also effects how sections are placed discard All orphan sections are discarded, by placing them in the DISCARD section see Output Section Discarding warn The linker will place the orphan section as for place and also issue a warning error The linker will exit with an error if any orphan section is found. The default if --orphan-handling is not given is place.--unique SECTION Creates a separate output section for every input section matching SECTION or if the optional wildcard SECTION argument is missing, for every orphan input section An orphan section is one not specifically mentioned in a linker script You may use this option multiple times on the command line It prevents the normal merging of input sections with the same name, overriding output section assignments in a linker script.-v --version - V Display the version number for ld The - V option also lists the supported emulations.-x --discard-all Delete all local symbols.-X --discard-locals Delete all temporary local symbols These symbols start with system-specific local label prefixes, typically L for ELF systems or L for traditional systems.-y symbol --trace-symbol symbol Print the name of each linked file in which symbol appears This option may be given any number of times On many systems it is necessary to prepend an underscore. This option is useful when you have an undefined symbol in your link but don t know where the reference is coming from.-Y path Add path to the default library search path This option exists for Solaris compatibility.-z keyword The recognized keywords are combreloc Combines multiple reloc sections and sorts them to make dynamic symbol lookup caching possible common Generate common symbols with the STTCOMMON type druing a relocatable link defs Disallows undefined symbols in object files Un defined symbols in shared libraries are still allowed execstack Marks the object as requiring executable stack global This option is only meaningful when building a shared object It makes the symbols defined by this shared object available for symbol resolution of subsequently loaded libraries initfirst This option is only meaningful when building a shared object It marks the object so that its runtime initialization will occur before the runtime initialization of any other objects brought into the process at the same time Similarly the runtime finalization of the object will occur after the runtime finalization of any other objects interpose Marks the object that its symbol table interposes before all symbols but the primary executable lazy When generating an executable or shared library, mark it to tell the dynamic linker to defer function call resolution to the point when the function is called lazy binding , rather than at load time Lazy binding is the default loadfltr Marks the ob ject that its filters be processed immediately at runtime muldefs Allows multiple definitions nocombreloc Disables multiple reloc sections combining nocommon Generate common symbols with the STTOBJECT type druing a relocatable link nocopyreloc Disable linker generated variables used in place of variables defined in shared libraries May result in dynamic text relocations nodefaultlib Marks the object that the search for dependencies of this object will ignore any default library search paths nodelete Marks the object shouldn t be unloaded at runtime nodlopen Marks the object not available to dlopen nodump Marks the object can not be dumped by dldump noexecstack Marks the object as not requiring executable stack text Treat DTTEXTREL in shared object as error notext Don t treat DTTEXTREL in shared object as error textoff Don t treat DTTEXTREL in shared object as error norelro Don t create an ELF PTGNURELRO segment header in the object now When generating an executable or shared library, m ark it to tell the dynamic linker to resolve all symbols when the program is started, or when the shared library is linked to using dlopen, instead of deferring function call resolution to the point when the function is first called origin Marks the object may contain ORIGIN relro Create an ELF PTGNURELRO segment header in the object max-page-size value Set the emulation maximum page size to value common-page-size value Set the emulation common page size to value stack-size value Specify a stack size for in an ELF PTGNUSTACK segment Specifying zero will override any default non-zero sized PTGNUSTACK segment creation bndplt Always generate BND prefix in PLT entries Supported for Linux x8664 noextern-protected-data Don t treat protected data symbol as external when building shared library This option overrides linker backend default It can be used to workaround incorrect relocations against protected data symbols generated by compiler Updates on protected data symbols by another module a ren t visible to the resulting shared library Supported for i386 and x86-64 nodynamic-undefined-weak Don t treat undefined weak symbols as dynamic when building executable This option overrides linker backend default It can be used to avoid dynamic relocations against undefined weak symbols in executable Supported for i386 and x86-64 noreloc-overflow Disable relocation overflow check This can be used to disable relocation overflow check if there will be no dynamic relocation overflow at run-time Supported for x8664 call-nop prefix-addr call-nop prefix-nop call-nop suffix-nop call-nop prefix - byte call-nop suffix - byte Specify the 1-byte NOP padding when transforming indirect call to a locally defined function, foo, via its GOT slot call-nop prefix-addr generates 0x67 call foo call-nop prefix-nop generates 0x90 call foo call-nop suffix-nop generates call foo 0x90 call-nop prefix - byte generates byte call foo call-nop suffix - byte generates call foo byte Supported for i386 and x8664.Othe r keywords are ignored for Solaris compatibility.- archives - --start-group archives --end-group The archives should be a list of archive files They may be either explicit file names, or - l options. The specified archives are searched repeatedly until no new undefined references are created Normally, an archive is searched only once in the order that it is specified on the command line If a symbol in that archive is needed to resolve an undefined symbol referred to by an object in an archive that appears later on the command line, the linker would not be able to resolve that reference By grouping the archives, they all be searched repeatedly until all possible references are resolved. Using this option has a significant performance cost It is best to use it only when there are unavoidable circular references between two or more archives.--accept-unknown-input-arch --no-accept-unknown-input-arch Tells the linker to accept input files whose architecture cannot be recognised The assumption is that the user knows what they are doing and deliberately wants to link in these unknown input files This was the default behaviour of the linker, before release 2 14 The default behaviour from release 2 14 onwards is to reject such input files, and so the --accept-unknown-input-arch option has been added to restore the old behaviour.--as-needed --no-as-needed This option affects ELF DTNEEDED tags for dynamic libraries mentioned on the command line after the --as-needed option Normally the linker will add a DTNEEDED tag for each dynamic library mentioned on the command line, regardless of whether the library is actually needed or not --as-needed causes a DTNEEDED tag to only be emitted for a library that at that point in the link satisfies a non-weak undefined symbol reference from a regular object file or, if the library is not found in the DTNEEDED lists of other needed libraries, a non-weak undefined symbol reference from another needed dynamic library Object files or libraries ap pearing on the command line after the library in question do not affect whether the library is seen as needed This is similar to the rules for extraction of object files from archives --no-as-needed restores the default behaviour.--add-needed --no-add-needed These two options have been deprecated because of the similarity of their names to the --as-needed and --no-as-needed options They have been replaced by --copy-dt-needed-entries and --no-copy-dt-needed-entries.-assert keyword This option is ignored for SunOS compatibility.-Bdynamic - dy - callshared Link against dynamic libraries This is only meaningful on platforms for which shared libraries are supported This option is normally the default on such platforms The different variants of this option are for compatibility with various systems You may use this option multiple times on the command line it affects library searching for - l options which follow it.-Bgroup Set the DF1GROUP flag in the DTFLAGS1 entry in the dynamic section This causes the runtime linker to handle lookups in this object and its dependencies to be performed only inside the group --unresolved-symbols report-all is implied This option is only meaningful on ELF platforms which support shared libraries.-Bstatic - dn - nonshared - static Do not link against shared libraries This is only meaningful on platforms for which shared libraries are supported The different variants of this option are for compatibility with various systems You may use this option multiple times on the command line it affects library searching for - l options which follow it This option also implies --unresolved-symbols report-all This option can be used with - shared Doing so means that a shared library is being created but that all of the library s external references must be resolved by pulling in entries from static libraries.-Bsymbolic When creating a shared library, bind references to global symbols to the definition within the shared library, if any Normally, it is possible for a program linked against a shared library to override the definition within the shared library This option can also be used with the --export-dynamic option, when creating a position independent executable, to bind references to global symbols to the definition within the executable This option is only meaningful on ELF platforms which support shared libraries and position independent executables.-Bsymbolic-functions When creating a shared library, bind references to global function symbols to the definition within the shared library, if any This option can also be used with the --export-dynamic option, when creating a position independent executable, to bind references to global function symbols to the definition within the executable This option is only meaningful on ELF platforms which support shared libraries and position independent executables.--dynamic-list dynamic-list-file Specify the name of a dynamic list file to the linker This is typically used when creating shared li braries to specify a list of global symbols whose references shouldn t be bound to the definition within the shared library, or creating dynamically linked executables to specify a list of symbols which should be added to the symbol table in the executable This option is only meaningful on ELF platforms which support shared libraries. The format of the dynamic list is the same as the version node without scope and node name See VERSION for more information.--dynamic-list-data Include all global data symbols to the dynamic list.--dynamic-list-cpp-new Provide the builtin dynamic list for C operator new and delete It is mainly useful for building shared libstdc.--dynamic-list-cpp-typeinfo Provide the builtin dynamic list for C runtime type identification.--check-sections --no-check-sections Asks the linker not to check section addresses after they have been assigned to see if there are any overlaps Normally the linker will perform this check, and if it finds any overlaps it will produce su itable error messages The linker does know about, and does make allowances for sections in overlays The default behaviour can be restored by using the command line switch --check-sections Section overlap is not usually checked for relocatable links You can force checking in that case by using the --check-sections option.--copy-dt-needed-entries --no-copy-dt-needed-entries This option affects the treatment of dynamic libraries referred to by DTNEEDED tags inside ELF dynamic libraries mentioned on the command line Normally the linker won t add a DTNEEDED tag to the output binary for each library mentioned in a DTNEEDED tag in an input dynamic library With --copy-dt-needed-entries specified on the command line however any dynamic libraries that follow it will have their DTNEEDED entries added The default behaviour can be restored with --no-copy-dt-needed-entries. This option also has an effect on the resolution of symbols in dynamic libraries With --copy-dt-needed-entries dynamic libraries mentioned on the command line will be recursively searched, following their DTNEEDED tags to other libraries, in order to resolve symbols required by the output binary With the default setting however the searching of dynamic libraries that follow it will stop with the dynamic library itself No DTNEEDED links will be traversed to resolve symbols.--cref Output a cross reference table If a linker map file is being generated, the cross reference table is printed to the map file Otherwise, it is printed on the standard output. The format of the table is intentionally simple, so that it may be easily processed by a script if necessary The symbols are printed out, sorted by name For each symbol, a list of file names is given If the symbol is defined, the first file listed is the location of the definition If the symbol is defined as a common value then any files where this happens appear next Finally any files that reference the symbol are listed.--no-define-common This option inhibits the a ssignment of addresses to common symbols The script command INHIBITCOMMONALLOCATION has the same effect See Miscellaneous Commands. The --no-define-common option allows decoupling the decision to assign addresses to Common symbols from the choice of the output file type otherwise a non-Relocatable output type forces assigning addresses to Common symbols Using --no-define-common allows Common symbols that are referenced from a shared library to be assigned addresses only in the main program This eliminates the unused duplicate space in the shared library, and also prevents any possible confusion over resolving to the wrong duplicate when there are many dynamic modules with specialized search paths for runtime symbol resolution.--defsym symbol expression Create a global symbol in the output file, containing the absolute address given by expression You may use this option as many times as necessary to define multiple symbols in the command line A limited form of arithmetic is supported for the expression in this context you may give a hexadecimal constant or the name of an existing symbol, or use and - to add or subtract hexadecimal constants or symbols If you need more elaborate expressions, consider using the linker command language from a script see Assignments Note there should be no white space between symbol the equals sign , and expression.--demangle style --no-demangle These options control whether to demangle symbol names in error messages and other output When the linker is told to demangle, it tries to present symbol names in a readable fashion it strips leading underscores if they are used by the object file format, and converts C mangled symbol names into user readable names Different compilers have different mangling styles The optional demangling style argument can be used to choose an appropriate demangling style for your compiler The linker will demangle by default unless the environment variable COLLECTNODEMANGLE is set These options may be used to ove rride the default.-I file --dynamic-linker file Set the name of the dynamic linker This is only meaningful when generating dynamically linked ELF executables The default dynamic linker is normally correct don t use this unless you know what you are doing.--no-dynamic-linker When producing an executable file, omit the request for a dynamic linker to be used at load-time This is only meaningful for ELF executables that contain dynamic relocations, and usually requires entry point code that is capable of processing these relocations.--fatal-warnings --no-fatal-warnings Treat all warnings as errors The default behaviour can be restored with the option --no-fatal-warnings.--force-exe-suffix Make sure that an output file has a suffix. If a successfully built fully linked output file does not have a or suffix, this option forces the linker to copy the output file to one of the same name with a suffix This option is useful when using unmodified Unix makefiles on a Microsoft Windows host, since some versions of Windows won t run an image unless it ends in a suffix.--gc-sections --no-gc-sections Enable garbage collection of unused input sections It is ignored on targets that do not support this option The default behaviour of not performing this garbage collection can be restored by specifying --no-gc-sections on the command line Note that garbage collection for COFF and PE format targets is supported, but the implementation is currently considered to be experimental. --gc-sections decides which input sections are used by examining symbols and relocations The section containing the entry symbol and all sections containing symbols undefined on the command-line will be kept, as will sections containing symbols referenced by dynamic objects Note that when building shared libraries, the linker must assume that any visible symbol is referenced Once this initial set of sections has been determined, the linker recursively marks as used any section referenced by their relocations See --entry and --undefined. This option can be set when doing a partial link enabled with option - r In this case the root of symbols kept must be explicitly specified either by an --entry or --undefined option or by a ENTRY command in the linker script.--print-gc-sections --no-print-gc-sections List all sections removed by garbage collection The listing is printed on stderr This option is only effective if garbage collection has been enabled via the --gc-sections option The default behaviour of not listing the sections that are removed can be restored by specifying --no-print-gc-sections on the command line.--gc-keep-exported When --gc-sections is enabled, this option prevents garbage collection of unused input sections that contain global symbols having default or protected visibility This option is intended to be used for executables where unreferenced sections would otherwise be garbage collected regardless of the external visibility of contained symbols Note that this option has no effect when linking shared objects since it is already the default behaviour This option is only supported for ELF format targets.--print-output-format Print the name of the default output format perhaps influenced by other command-line options This is the string that would appear in an OUTPUTFORMAT linker script command see File Commands.--print-memory-usage Print used size, total size and used size of memory regions created with the MEMORY command This is useful on embedded targ ets to have a quick view of amount of free memory The format of the output has one headline and one line per region It is both human readable and easily parsable by tools Here is an example of an output.--help Print a summary of the command-line options on the standard output and exit.--target-help Print a summary of all target specific options on the standard output and exit.-Map mapfile Print a link map to the file mapfile See the description of the - M option, above.--no-keep-memory ld normally optimizes for speed over memory usage by caching the symbol tables of input files in memory This option tells ld to instead optimize for memory usage, by rereading the symbol tables as necessary This may be required if ld runs out of memory space while linking a large executable.--no-undefined - z defs Report unresolved symbol references from regular object files This is done even if the linker is creating a non-symbolic shared library The switch -- no - allow-shlib-undefined controls the behavi our for reporting unresolved references found in shared libraries being linked in.--allow-multiple-definition - z muldefs Normally when a symbol is defined multiple times, the linker will report a fatal error These options allow multiple definitions and the first definition will be used.--allow-shlib-undefined --no-allow-shlib-undefined Allows or disallows undefined symbols in shared libraries This switch is similar to --no-undefined except that it determines the behaviour when the undefined symbols are in a shared library rather than a regular object file It does not affect how undefined symbols in regular object files are handled. The default behaviour is to report errors for any undefined symbols referenced in shared libraries if the linker is being used to create an executable, but to allow them if the linker is being used to create a shared library. The reasons for allowing undefined symbol references in shared libraries specified at link time are that. A shared library specified at l ink time may not be the same as the one that is available at load time, so the symbol might actually be resolvable at load time. There are some operating systems, eg BeOS and HPPA, where undefined symbols in shared libraries are normal. The BeOS kernel for example patches shared libraries at load time to select whichever function is most appropriate for the current architecture This is used, for example, to dynamically select an appropriate memset function.--no-undefined-version Normally when a symbol has an undefined version, the linker will ignore it This option disallows symbols with undefined version and a fatal error will be issued instead.--default-symver Create and use a default symbol version the soname for unversioned exported symbols.--default-imported-symver Create and use a default symbol version the soname for unversioned imported symbols.--no-warn-mismatch Normally ld will give an error if you try to link together input files that are mismatched for some reason, perhaps bec ause they have been compiled for different processors or for different endiannesses This option tells ld that it should silently permit such possible errors This option should only be used with care, in cases when you have taken some special action that ensures that the linker errors are inappropriate.--no-warn-search-mismatch Normally ld will give a warning if it finds an incompatible library during a library search This option silences the warning.--no-whole-archive Turn off the effect of the --whole-archive option for subsequent archive files.--noinhibit-exec Retain the executable output file whenever it is still usable Normally, the linker will not produce an output file if it encounters errors during the link process it exits without writing an output file when it issues any error whatsoever.-nostdlib Only search library directories explicitly specified on the command line Library directories specified in linker scripts including linker scripts specified on the command line are ig nored.--oformat output-format ld may be configured to support more than one kind of object file If your ld is configured this way, you can use the --oformat option to specify the binary format for the output object file Even when ld is configured to support alternative object formats, you don t usually need to specify this, as ld should be configured to produce as a default output format the most usual format on each machine output-format is a text string, the name of a particular format supported by the BFD libraries You can list the available binary formats with objdump - i The script command OUTPUTFORMAT can also specify the output format, but this option overrides it See BFD.--out-implib file Create an import library in file corresponding to the executable the linker is generating eg a DLL or ELF program This import library which should be called or a for DLLs may be used to link clients against the generated executable this behaviour makes it possible to skip a separate import libr ary creation step eg dlltool for DLLs This option is only available for the i386 PE and ELF targetted ports of the linker.-pie --pic-executable Create a position independent executable This is currently only supported on ELF platforms Position independent executables are similar to shared libraries in that they are relocated by the dynamic linker to the virtual address the OS chooses for them which can vary between invocations Like normal dynamically linked executables they can be executed and symbols defined in the executable cannot be overridden by shared libraries.-qmagic This option is ignored for Linux compatibility.-Qy This option is ignored for SVR4 compatibility. On some platforms the --relax option performs target specific, global optimizations that become possible when the linker resolves addressing in the program, such as relaxing address modes, synthesizing new instructions, selecting shorter version of current instructions, and combining constant values. On some platforms th ese link time global optimizations may make symbolic debugging of the resulting executable impossible This is known to be the case for the Matsushita MN10200 and MN10300 family of processors. On platforms where this is not supported, --relax is accepted, but ignored. On platforms where --relax is accepted the option --no-relax can be used to disable the feature.--retain-symbols-file filename Retain only the symbols listed in the file filename discarding all others filename is simply a flat file, with one symbol name per line This option is especially useful in environments such as VxWorks where a large global symbol table is accumulated gradually, to conserve run-time memory. --retain-symbols-file does not discard undefined symbols, or symbols needed for relocations. You may only specify --retain-symbols-file once in the command line It overrides - s and - S - rpath dir Add a directory to the runtime library search path This is used when linking an ELF executable with shared objects All - rpath arguments are concatenated and passed to the runtime linker, which uses them to locate shared objects at runtime The - rpath option is also used when locating shared objects which are needed by shared objects explicitly included in the link see the description of the - rpath-link option If - rpath is not used when linking an ELF executable, the contents of the environment variable LDRUNPATH will be used if it is defined. The - rpath option may also be used on SunOS By default, on SunOS, the linker will form a runtime search path out of all the - L options it is given If a - rpath option is used, the runtime search path will be formed exclusively using the - rpath options, ignorin g the - L options This can be useful when using gcc, which adds many - L options which may be on NFS mounted file systems. For compatibility with other ELF linkers, if the - R option is followed by a directory name, rather than a file name, it is treated as the - rpath option.-rpath-link dir When using ELF or SunOS, one shared library may require another This happens when an ld - shared link includes a shared library as one of the input files. When the linker encounters such a dependency when doing a non-shared, non-relocatable link, it will automatically try to locate the required shared library and include it in the link, if it is not included explicitly In such a case, the - rpath-link option specifies the first set of directories to search The - rpath-link option may specify a sequence of directory names either by specifying a list of names separated by colons, or by appearing multiple times. The tokens ORIGIN and LIB can appear in these search directories They will be replaced by the full p ath to the directory containing the program or shared object in the case of ORIGIN and either lib - for 32-bit binaries - or lib64 - for 64-bit binaries - in the case of LIB. The alternative form of these tokens - and can also be used The token PLATFORM is not supported. This option should be used with caution as it overrides the search path that may have been hard compiled into a shared library In such a case it is possible to use unintentionally a different search path than the runtime linker would do. The linker uses the following search paths to locate required shared libraries. Any directories specified by - rpath-link options. Any directories specified by - rpath options The difference between - rpath and - rpath-link is that directories specified by - rpath options are included in the executable and used at runtime, whereas the - rpath-link option is only effective at link time Searching - rpath in this way is only supported by native linkers and cross linkers which have been configured wit h the --with-sysroot option. On an ELF system, for native linkers, if the - rpath and - rpath-link options were not used, search the contents of the environment variable LDRUNPATH. On SunOS, if the - rpath option was not used, search any directories specified using - L options. For a native linker, search the contents of the environment variable LDLIBRARYPATH. For a native ELF linker, the directories in DTRUNPATH or DTRPATH of a shared library are searched for shared libraries needed by it The DTRPATH entries are ignored if DTRUNPATH entries exist. The default directories, normally lib and usr lib. For a native linker on an ELF system, if the file exists, the list of directories found in that file. If the required shared library is not found, the linker will issue a warning and continue with the link.-shared - Bshareable Create a shared library This is currently only supported on ELF, XCOFF and SunOS platforms On SunOS, the linker will automatically create a shared library if the - e option is not used and there are undefined symbols in the link.--sort-common --sort-common ascending --sort-common descending This option tells ld to sort the common symbols by alignment in ascending or descending order when it places them in the appropriate output sections The symbol alignments considered are sixteen-byte or larger, eight-byte, four-byte, two-byte, and one-byte This is to prevent gaps between symbols due to alignment constraints If no sorting order is specified, then descending order is assumed.--sort-section name This option will apply SORTBYNAME to all wildcard section patterns in the linker script.--sort-section alignment This option will apply SORTBYALIGNMENT to all wildcard section patterns in the linker script.--split-by-file size Similar to --split-by-reloc but creates a new output section for each input file when size is reached size defaults to a size of 1 if not given.--split-by-reloc count Tries to creates extra sections in the output file so that no single output sectio n in the file contains more than count relocations This is useful when generating huge relocatable files for downloading into certain real time kernels with the COFF object file format since COFF cannot represent more than 65535 relocations in a single section Note that this will fail to work with object file formats which do not support arbitrary sections The linker will not split up individual input sections for redistribution, so if a single input section contains more than count relocations one output section will contain that many relocations count defaults to a value of 32768.--stats Compute and display statistics about the operation of the linker, such as execution time and memory usage.--sysroot directory Use directory as the location of the sysroot, overriding the configure-time default This option is only supported by linkers that were configured using --with-sysroot.--traditional-format For some targets, the output of ld is different in some ways from the output of some exis ting linker This switch requests ld to use the traditional format instead. For example, on SunOS, ld combines duplicate entries in the symbol string table This can reduce the size of an output file with full debugging information by over 30 percent Unfortunately, the SunOS dbx program can not read the resulting program gdb has no trouble The --traditional-format switch tells ld to not combine duplicate entries.--section-start sectionname org Locate a section in the output file at the absolute address given by org You may use this option as many times as necessary to locate multiple sections in the command line org must be a single hexadecimal integer for compatibility with other linkers, you may omit the leading 0x usually associated with hexadecimal values Note there should be no white space between sectionname the equals sign , and org.-Tbss org - Tdata org - Ttext org Same as --section-start with data or as the sectionname.-Ttext-segment org When creating an ELF executable, it will set the address of the first byte of the text segment.-Trodata-segment org When creating an ELF executable or shared object for a target where the read-only data is in its own segment separate from the executable text, it will set the address of the first byte of the read-only data segment.-Tldata-segment org When creating an ELF executable or shared object for x86-64 medium memory model, it will set the address of the first byte of the ldata segment.--unresolved-symbols method Determine how to handle unresolved symbols There are four possible values for method ignore-all Do not report any unresolved symbols report-all Report all unresolved symbols This is the default ignore-in-object-files Report unresolved symbols that are contained in shared libraries, but ignore them if they come from regular object files ignore-in-shared-libs Report unresolved symbols that come from regular object files, but ignore them if they come from shared libraries This can be useful when creating a dynamic bin ary and it is known that all the shared libraries that it should be referencing are included on the linker s command line. The behaviour for shared libraries on their own can also be controlled by the -- no - allow-shlib-undefined option. Normally the linker will generate an error message for each reported unresolved symbol but the option --warn-unresolved-symbols can change this to a warning.--dll-verbose --verbose NUMBER Display the version number for ld and list the linker emulations supported Display which input files can and cannot be opened Display the linker script being used by the linker If the optional NUMBER argument 1, plugin symbol status will also be displayed.--version-script version-scriptfile Specify the name of a version script to the linker This is typically used when creating shared libraries to specify additional information about the version hierarchy for the library being created This option is only fully supported on ELF platforms which support shared libraries see VERSION It is partially supported on PE platforms, which can use version scripts to filter symbol visibility in auto-export mode any symbols marked local in the version script will not be exported See WIN32.--warn-common Warn when a common symbol is combined with another common symbol or with a symbol definition Unix linkers allow this somewhat sloppy practice, but linkers on some other operating systems do not This option allows you to find potential problems from combining global symbols Unfortunately, some C libraries use this practice, so you may get some warnings about symbols in the libraries as well as in your programs. There are three kinds of global symbols, illustrated here by C examples int i 1 A definition, which goes in the initialized data section of the output file extern int i An undefined reference, which does not allocate space There must be either a definition or a common symbol for the variable somewhere int i A common symbol If there are only one or more common sym bols for a variable, it goes in the uninitialized data area of the output file The linker merges multiple common symbols for the same variable into a single symbol If they are of different sizes, it picks the largest size The linker turns a common symbol into a declaration, if there is a definition of the same variable. The --warn-common option can produce five kinds of warnings Each warning consists of a pair of lines the first describes the symbol just encountered, and the second describes the previous symbol encountered with the same name One or both of the two symbols will be a common symbol. Turning a common symbol into a reference, because there is already a definition for the symbol. Turning a common symbol into a reference, because a later definition for the symbol is encountered This is the same as the previous case, except that the symbols are encountered in a different order. Merging a common symbol with a previous same-sized common symbol. Merging a common symbol with a previous larger common symbol. Merging a common symbol with a previous smaller common symbol This is the same as the previous case, except that the symbols are encountered in a different order.--warn-constructors Warn if any global constructors are used This is only useful for a few object file formats For formats like COFF or ELF, the linker can not detect the use of global constructors.--warn-multiple-gp Warn if multiple global pointer values are required in the output file This is only meaningful for certain processors, such as the Alpha Specifically, some processors put large-valued constants in a special section A special register the global pointer points into the middle of this section, so that constants can be loaded efficiently via a base-register relative addressing mode Since the offset in base-register relative mode is fixed and relatively small e g 16 bits , this limits the maximum size of the constant pool Thus, in large programs, it is often necessary to use multiple global point er values in order to be able to address all possible constants This option causes a warning to be issued whenever this case occurs.--warn-once Only warn once for each undefined symbol, rather than once per module which refers to it.--warn-section-align Warn if the address of an output section is changed because of alignment Typically, the alignment will be set by an input section The address will only be changed if it not explicitly specified that is, if the SECTIONS command does not specify a start address for the section see SECTIONS.--warn-shared-textrel Warn if the linker adds a DTTEXTREL to a shared object.--warn-alternate-em Warn if an object has alternate ELF machine code.--warn-unresolved-symbols If the linker is going to report an unresolved symbol see the option --unresolved-symbols it will normally generate an error This option makes it generate a warning instead.--error-unresolved-symbols This restores the linker s default behaviour of generating errors when it is reportin g unresolved symbols.--whole-archive For each archive mentioned on the command line after the --whole-archive option, include every object file in the archive in the link, rather than searching the archive for the required object files This is normally used to turn an archive file into a shared library, forcing every object to be included in the resulting shared library This option may be used more than once. Two notes when using this option from gcc First, gcc doesn t know about this option, so you have to use - Wl,-whole-archive Second, don t forget to use - Wl,-no-whole-archive after your list of archives, because gcc will add its own list of archives to your link and you may not want this flag to affect those as well.--wrap symbol Use a wrapper function for symbol Any undefined reference to symbol will be resolved to wrap symbol Any undefined reference to real symbol will be resolved to symbol. This can be used to provide a wrapper for a system function The wrapper function should be c alled wrap symbol If it wishes to call the system function, it should call real symbol. Here is a trivial example. If you link other code with this file using --wrap malloc then all calls to malloc will call the function wrapmalloc instead The call to realmalloc in wrapmalloc will call the real malloc function. You may wish to provide a realmalloc function as well, so that links without the --wrap option will succeed If you do this, you should not put the definition of realmalloc in the same file as wrapmalloc if you do, the assembler may resolve the call before the linker has a chance to wrap it to malloc.--eh-frame-hdr --no-eh-frame-hdr Request --eh-frame-hdr or suppress --no-eh-frame-hdr the creation of section and ELF PTGNUEHFRAME segment header.--no-ld-generated-unwind-info Request creation of unwind info for linker generated code sections like PLT This option is on by default if linker generated unwind info is supported.--enable-new-dtags --disable-new-dtags This linker can create the new dynamic tags in ELF But the older ELF systems may not understand them If you specify --enable-new-dtags the new dynamic tags will be created as needed and older dynamic tags will be omitted If you specify --disable-new-dtags no new dynamic tags will be created By default, the new dynamic tags are not created Note that those options are only available for ELF systems.--hash-size number Set the default size of the linker s hash tables to a prime number close to number Increasing this value can reduce the length of time it takes the linker to perform its tasks, at the expense of increasing the linker s memory requirements Similarly reducing this value can reduce the memory requirements at the expense of speed.--hash-style style Set the type of linker s hash table s style can be either sysv for classic ELF section, gnu for new style GNU section or both for both the classic ELF and new style GNU hash tables The default is sysv.--compress-debug-sections none --compress-debug-sections zlib --compress-debug-sections zlib-gnu --compress-debug-sections zlib-gabi On ELF platforms, these options control how DWARF debug sections are compressed using zlib.--compress-debug-sections none doesn t compress DWARF debug sections --compress-debug-sections zlib-gnu compresses DWARF debug sections and renames them to begin with instead of --compress-debug-sections zlib-gabi also compresses DWARF debug sections, but rather than renaming them it sets the SHFCOMPRESSED flag in the sections headers. The --compress-debug-sections zlib option is an alias for --compress-debug-sections zlib-gabi. Note that this option overrides any compression in input debug sections, so if a binary is linked with --compress-debug-sections none for example, then any compressed debug sections in input files will be uncompressed before they are copied into the output binary. The default compression behaviour varies depending upon the target involved and the configure options used to build the toolchain The def ault can be determined by examining the output from the linker s --help option.--reduce-memory-overheads This option reduces memory requirements at ld runtime, at the expense of linking speed This was introduced to select the old O n 2 algorithm for link map file generation, rather than the new O n algorithm which uses about 40 more memory for symbol storage. Another effect of the switch is to set the default hash table size to 1021, which again saves memory at the cost of lengthening the linker s run time This is not done however if the --hash-size switch has been used. The --reduce-memory-overheads switch may be also be used to enable other tradeoffs in future versions of the linker.--build-id --build-id style Request the creation of a ELF note section or a COFF section The contents of the note are unique bits identifying this linked file style can be uuid to use 128 random bits, sha1 to use a 160-bit SHA1 hash on the normative parts of the output contents, md5 to use a 128-bit MD5 has h on the normative parts of the output contents, or 0x hexstring to use a chosen bit string specified as an even number of hexadecimal digits - and characters between digit pairs are ignored If style is omitted, sha1 is used. The md5 and sha1 styles produces an identifier that is always the same in an identical output file, but will be unique among all nonidentical output files It is not intended to be compared as a checksum for the file s contents A linked file may be changed later by other tools, but the build ID bit string identifying the original linked file does not change. Passing none for style disables the setting from any --build-id options earlier on the command line.2 1 1 Options Specific to i386 PE Targets. The i386 PE linker supports the - shared option, which causes the output to be a dynamically linked library DLL instead of a normal executable You should name the output when you use this option In addition, the linker fully supports the standard files, which may be specifie d on the linker command line like an object file in fact, it should precede archives it exports symbols from, to ensure that they get linked in, just like a normal object file. In addition to the options common to all targets, the i386 PE linker support additional command line options that are specific to the i386 PE target Options that take values may be separated from their values by either a space or an equals sign --add-stdcall-alias If given, symbols with a stdcall suffix nn will be exported as-is and also with the suffix stripped This option is specific to the i386 PE targeted port of the linker.--base-file file Use file as the name of a file in which to save the base addresses of all the relocations needed for generating DLLs with dlltool This is an i386 PE specific option.--dll Create a DLL instead of a regular executable You may also use - shared or specify a LIBRARY in a given file This option is specific to the i386 PE targeted port of the linker.--enable-long-section-names -- disable-long-section-names The PE variants of the COFF object format add an extension that permits the use of section names longer than eight characters, the normal limit for COFF By default, these names are only allowed in object files, as fully-linked executable images do not carry the COFF string table required to support the longer names As a GNU extension, it is possible to allow their use in executable images as well, or to probably pointlessly disallow it in object files, by using these two options Executable images generated with these long section names are slightly non-standard, carrying as they do a string table, and may generate confusing output when examined with non-GNU PE-aware tools, such as file viewers and dumpers However, GDB relies on the use of PE long section names to find Dwarf-2 debug information sections in an executable image at runtime, and so if neither option is specified on the command-line, ld will enable long section names, overriding the default and tec hnically correct behaviour, when it finds the presence of debug information while linking an executable image and not stripping symbols This option is valid for all PE targeted ports of the linker.--enable-stdcall-fixup --disable-stdcall-fixup If the link finds a symbol that it cannot resolve, it will attempt to do fuzzy linking by looking for another defined symbol that differs only in the format of the symbol name cdecl vs stdcall and will resolve that symbol by linking to the match For example, the undefined symbol foo might be linked to the function foo 12 or the undefined symbol bar 16 might be linked to the function bar When the linker does this, it prints a warning, since it normally should have failed to link, but sometimes import libraries generated from third-party dlls may need this feature to be usable If you specify --enable-stdcall-fixup this feature is fully enabled and warnings are not printed If you specify --disable-stdcall-fixup this feature is disabled and such mism atches are considered to be errors This option is specific to the i386 PE targeted port of the linker.--leading-underscore --no-leading-underscore For most targets default symbol-prefix is an underscore and is defined in target s description By this option it is possible to disable enable the default underscore symbol-prefix.--export-all-symbols If given, all global symbols in the objects used to build a DLL will be exported by the DLL Note that this is the default if there otherwise wouldn t be any exported symbols When symbols are explicitly exported via DEF files or implicitly exported via function attributes, the default is to not export anything else unless this option is given Note that the symbols DllMain 12 DllEntryPoint 0 DllMainCRTStartup 12 and impureptr will not be automatically exported Also, symbols imported from other DLLs will not be re-exported, nor will symbols specifying the DLL s internal layout such as those beginning with head or ending with iname In addition, no symbols from libgcc libstd libmingw32 or crtX o will be exported Symbols whose names begin with rtti or builtin will not be exported, to help with C DLLs Finally, there is an extensive list of cygwin-private symbols that are not exported obviously, this applies on when building DLLs for cygwin targets These cygwin-excludes are cygwindllentry 12 cygwincrt0common 8 cygwinnoncygwindllentry 12 fmode impureptr cygwinattachdll cygwinpremain0 cygwinpremain1 cygwinpremain2 cygwinpremain3 and environ This option is specific to the i386 PE targeted port of the linker.--exclude-symbols symbol symbol Specifies a list of symbols which should not be automatically exported The symbol names may be delimited by commas or colons This option is specific to the i386 PE targeted port of the linker.--exclude-all-symbols Specifies no symbols should be automatically exported This option is specific to the i386 PE targeted port of the linker.--file-alignment Specify the file alignment Sections in the file will always begin at file offsets which are multiples of this number This defaults to 512 This option is specific to the i386 PE targeted port of the linker.--heap reserve --heap reserve commit Specify the number of bytes of memory to reserve and optionally commit to be used as heap for this program The default is 1MB reserved, 4K committed This option is specific to the i386 PE targeted port of the linker.--image-base value Use value as the base address of your program or dll This is the lowest memory location that will be used when your program or dll is loaded To reduce the need to relocate and improve performance of your dlls, each should have a unique base address and not overlap any other dlls The default is 0x400000 for executables, and 0x10000000 for dlls This option is specific to the i386 PE targeted port of the linker.--kill-at If given, the stdcall suffixes nn will be stripped from symbols before they are exported This option is specific to the i386 PE targeted port of the link er.--large-address-aware If given, the appropriate bit in the Characteristics field of the COFF header is set to indicate that this executable supports virtual addresses greater than 2 gigabytes This should be used in conjunction with the 3GB or USERVA value megabytes switch in the operating systems section of the Otherwise, this bit has no effect This option is specific to PE targeted ports of the linker.--disable-large-address-aware Reverts the effect of a previous --large-address-aware option This is useful if --large-address-aware is always set by the compiler driver e g Cygwin gcc and the executable does not support virtual addresses greater than 2 gigabytes This option is specific to PE targeted ports of the linker.--major-image-version value Sets the major number of the image version Defaults to 1 This option is specific to the i386 PE targeted port of the linker.--major-os-version value Sets the major number of the os version Defaults to 4 This option is specific to the i386 PE targeted port of the linker.--major-subsystem-version value Sets the major number of the subsystem version Defaults to 4 This option is specific to the i386 PE targeted port of the linker.--minor-image-version value Sets the minor number of the image version Defaults to 0 This option is specific to the i386 PE targeted port of the linker.--minor-os-version value Sets the minor number of the os version Defaults to 0 This option is specific to the i386 PE targeted port of the linker.--minor-subsystem-version value Sets the minor number of the subsystem version Defaults to 0 This option is specific to the i386 PE targeted port of the linker.--output-def file The linker will create the file file which will contain a DEF file corresponding to the DLL the linker is generating This DEF file which should be called may be used to create an import library with dlltool or may be used as a reference to automatically or implicitly exported symbols This option is specific to the i386 PE targeted po rt of the linker.--enable-auto-image-base --enable-auto-image-base value Automatically choose the image base for DLLs, optionally starting with base value unless one is specified using the --image-base argument By using a hash generated from the dllname to create unique image bases for each DLL, in-memory collisions and relocations which can delay program execution are avoided This option is specific to the i386 PE targeted port of the linker.--disable-auto-image-base Do not automatically generate a unique image base If there is no user-specified image base --image-base then use the platform default This option is specific to the i386 PE targeted port of the linker.--dll-search-prefix string When linking dynamically to a dll without an import library, search for string basename in preference to lib basename This behaviour allows easy distinction between DLLs built for the various subplatforms native, cygwin, uwin, pw, etc For instance, cygwin DLLs typically use --dll-search-prefix cyg This option is specific to the i386 PE targeted port of the linker.--enable-auto-import Do sophisticated linking of symbol to impsymbol for DATA imports from DLLs, and create the necessary thunking symbols when building the import libraries with those DATA exports Note Use of the auto-import extension will cause the text section of the image file to be made writable This does not conform to the PE-COFF format specification published by Microsoft. Note - use of the auto-import extension will also cause read only data which would normally be placed into the section to be placed into the section instead This is in order to work around a problem with consts that is described here. Using auto-import generally will just work but sometimes you may see this message. variable var can t be auto-imported Please read the documentation for ld s --enable-auto-import for details. This message occurs when some sub expression accesses an address ultimately given by the sum of two constants Win32 import tables only allow one Instances where this may occur include accesses to member fields of struct variables imported from a DLL, as well as using a constant index into an array variable imported from a DLL Any multiword variable arrays, structs, long long, etc may trigger this error condition However, regardless of the exact data type of the offending exported variable, ld will always detect it, issue the warning, and exit. There are several ways to address this difficulty, regardless of the data type of the exported variable. One way is to use enable-runtime-pseudo-reloc switch This leaves the task of adjusting references in your client code for runtime environment, so this method works only when runtime environment supports this feature. A second solution is to force one of the constants to be a variable that is, unknown and un-optimizable at compile time For arrays, there are two possibilities a make the indexee the array s address a variable, or b make the constant index a variable Thus. For structs and most other multiword data types the only option is to make the struct itself or the long long, or the variable. A third method of dealing with this difficulty is to abandon auto-import for the offending symbol and mark it with declspec dllimport However, in practice that requires using compile-time defines to indicate whether you are building a DLL, building client code that will link to the DLL, or merely building linking to a static library In making the choice between the various methods of resolving the direct address with constant offset problem, you should consider typical real-world usage. A fourth way to avoid this problem is to re-code your library to use a functional interface rather than a data interface for the offending variables e g setfoo and getfoo accessor functions This option is specific to the i386 PE targeted port of the linker.--disable-auto-import Do not attempt to do sophisticated linking of symbol to impsymbol for DATA imports from DLLs This option is specific to the i386 PE targeted port of the linker.--enable-runtime-pseudo-reloc If your code contains expressions described in enable-auto-import section, that is, DATA imports from DLL with non-zero offset, this switch will create a vector of runtime pseudo relocations which can be used by runtime environment to adjust references to such data in your client code This option is specific to the i386 PE targeted port of the linker.--disable-runtime-pseudo-reloc Do not create pseudo relocations for non-zero offset DATA imports from DLLs This option is specific to the i386 PE targeted port of the linker.--enable-extra-pe-debug Show additional debug info related to auto-import symbol thunking This option is specific to the i386 PE targeted port of the lin ker.--section-alignment Sets the section alignment Sections in memory will always begin at addresses which are a multiple of this number Defaults to 0x1000 This option is specific to the i386 PE targeted port of the linker.--stack reserve --stack reserve commit Specify the number of bytes of memory to reserve and optionally commit to be used as stack for this program The default is 2MB reserved, 4K committed This option is specific to the i386 PE targeted port of the linker.--subsystem which --subsystem which major --subsystem which major minor Specifies the subsystem under which your program will execute The legal values for which are native windows console posix and xbox You may optionally set the subsystem version also Numeric values are also accepted for which This option is specific to the i386 PE targeted port of the linker. The following options set flags in the DllCharacteristics field of the PE file header These options are specific to PE targeted ports of the linker.--high-ent ropy-va Image is compatible with 64-bit address space layout randomization ASLR.--dynamicbase The image base address may be relocated using address space layout randomization ASLR This feature was introduced with MS Windows Vista for i386 PE targets.--forceinteg Code integrity checks are enforced.--nxcompat The image is compatible with the Data Execution Prevention This feature was introduced with MS Windows XP SP2 for i386 PE targets.--no-isolation Although the image understands isolation, do not isolate the image.--no-seh The image does not use SEH No SE handler may be called from this image.--no-bind Do not bind this image.--wdmdriver The driver uses the MS Windows Driver Model.--tsaware The image is Terminal Server aware.--insert-timestamp --no-insert-timestamp Insert a real timestamp into the image This is the default behaviour as it matches legacy code and it means that the image will work with other, proprietary tools The problem with this default is that it will result in sligh tly different images being produced each time the same sources are linked The option --no-insert-timestamp can be used to insert a zero value for the timestamp, this ensuring that binaries produced from identical sources will compare identically.2 1 2 Options specific to C6X uClinux targets. The C6X uClinux target uses a binary format called DSBT to support shared libraries Each shared library in the system needs to have a unique index all executables use an index of 0 --dsbt-size size This option sets the number of entries in the DSBT of the current executable or shared library to size The default is to create a table with 64 entries.--dsbt-index index This option sets the DSBT index of the current executable or shared library to index The default is 0, which is appropriate for generating executables If a shared library is generated with a DSBT index of 0, the RC6000DSBTINDEX relocs are copied into the output file. The --no-merge-exidx-entries switch disables the merging of adjacent exi dx entries in frame unwind info.2 1 3 Options specific to Motorola 68HC11 and 68HC12 targets. The 68HC11 and 68HC12 linkers support specific options to control the memory bank switching mapping and trampoline code generation --no-trampoline This option disables the generation of trampoline By default a trampoline is generated for each far function which is called using a jsr instruction this happens when a pointer to a far function is taken.--bank-window name This option indicates to the linker the name of the memory region in the MEMORY specification that describes the memory bank window The definition of such region is then used by the linker to compute paging and addresses within the memory window.2 1 4 Options specific to Motorola 68K target. The following options are supported to control handling of GOT generation when linking for 68K targets --got type This option tells the linker which GOT generation scheme to use type should be one of single , negative , multigot or target For mo re information refer to the Info entry for ld.2 1 5 Options specific to MIPS targets. The following options are supported to control microMIPS instruction generation and branch relocation checks for ISA mode transitions when linking for MIPS targets --insn32 --no-insn32 These options control the choice of microMIPS instructions used in code generated by the linker, such as that in the PLT or lazy binding stubs, or in relaxation If --insn32 is used, then the linker only uses 32-bit instruction encodings By default or if --no-insn32 is used, all instruction encodings are used, including 16-bit ones where possible.--ignore-branch-isa --no-ignore-branch-isa These options control branch relocation checks for invalid ISA mode transitions If --ignore-branch-isa is used, then the linker accepts any branch relocations and any ISA mode transition required is lost in relocation calculation, except for some cases of BAL instructions which meet relaxation conditions and are converted to equivalent J ALX instructions as the associated relocation is calculated By default or if --no-ignore-branch-isa is used a check is made causing the loss of an ISA mode transition to produce an error.