После двух лет разработки состоялся релиз Debian GNU/Linux 11.0 (Bullseye), доступный для девяти официально поддерживаемых архитектур: Intel IA-32/x86 (i686), AMD64 / x86-64, ARM EABI (armel), 64-bit ARM (arm64), ARMv7 (armhf), mipsel, mips64el, PowerPC 64 (ppc64el) и IBM System z (s390x). Обновления для Debian 11 будут выпускаться в течение 5 лет.
В репозитории представлено 59551 бинарных пакетов (42821 исходных пакетов), что примерно на 1848 пакетов больше, чем было предложено в Debian 10. По сравнению с Debian 10 добавлено 11294 новых бинарных пакетов, удалено 9519 (16%) устаревших или заброшенных пакетов, обновлено 42821 (72%) пакетов. Общий суммарных размер всех предложенных в дистрибутиве исходных текстов составляет 1 152 960 944 строк кода. В подготовке релиза приняло участие 6208 разработчиков.
Системные требования
Полезные ссылки
Подробное описание
Debian — операционная система является одной из старейших и популярных систем Linux
Debian GNU/Linux — операционная система на базе Linux с открытым исходным кодом, разработанная командой талантливых разработчиков и хакеров, которые стремились создать альтернативу существующим на тот момент дистрибутивам Linux, в частности Slackware.
Названный универсальной ОС (“The Universal Operating System”), Debian GNU Linux используется в качестве базовой платформы для сотен или даже тысяч дистрибутивов Linux, включая самую популярную бесплатную операционную систему — Ubuntu Linux.
Обзор Debian
Распространяется в виде ISO-образов для установки
Система распространяется с помощью образов для сетевой установки или ISO-образов на CD и DVD, предназначенных только для установки и поддерживающих 64-битную (amd64, kfreebsd-amd64, ia64), 32-битную (i386, kfreebsd-i386), Armel, Armhf, MIPS, PowerPC, SPARC, s390, s390x, и MIPSel архитектуры.
ISO образы также доступны для загрузки, но они поддерживают только сетевую установку. Последние версии ОС распространяются со средами рабочего стола KDE, Xfce и LXDE.
Live CD и Rescue CD доступны отдельно
Проект также поддерживает образы Live CD, которые предназначены только для машин с 32-битной и 64-битной архитектурой и могут применяться для использования или тестирования Debian с окружениями рабочего стола KDE, GNOME, Xfce или LXDE. Стандартные диски и диски восстановления (Rescue CD) также доступны для загрузки для пользователей, который желают использовать платформу Debian для выполнения административных и сервисных задач.
Включает богатый набор программ с открытым исходным кодом
Помимо приложений, которые являются частью сред рабочего стола GNOME, Xfce, KDE или LXDE, Debian GNU/Linux также включает большое количество сторонних приложений для редактирования файлов, просмотра потокового видео, прослушивания музыкальных файлов, а также многочисленные библиотеки ядра и пакеты разработки.
Не самый современный
К сожалению, для многих пользователей Debian GNU/Linux не является актуальным дистрибутивом Linux. Вместо этого, проект представляет собой стабильную операционную систему, которая включает более 37500 тестовых пакетов и прекомпилированное ПО для простой установки. Debian GNU/Linux — идеальный вариант для развертывания стабильной, надежной и мощной системы на машинах клиентов и знакомых.
Источник
Пакет: gcc-x86-64-linux-gnu (4:8.3.0-1)
Ссылки для gcc-x86-64-linux-gnu
Ресурсы Debian:
Исходный код gcc-defaults:
Сопровождающие:
Подобные пакеты:
GNU C compiler for the amd64 architecture
This is the GNU C compiler, a fairly portable optimizing compiler for C.
This is a dependency package providing the default GNU C cross-compiler for the amd64 architecture.
Другие пакеты, относящиеся к gcc-x86-64-linux-gnu
зависимости
рекомендации
предложения
enhances
dep: cpp-x86-64-linux-gnu (= 4:8.3.0-1) GNU C preprocessor (cpp) for the amd64 architecture
dep: gcc-8-x86-64-linux-gnu (>= 8.3.0-1
) GNU C compiler
rec: libc6-dev-amd64-cross GNU C Library: Development Libraries and Header Files (for cross-compiling) или libc-dev-amd64-cross виртуальный пакет, предоставляемый libc6-dev-amd64-cross
sug: autoconf automatic configure script builder
sug: automake Tool for generating GNU Standards-compliant Makefiles
sug: bison YACC-compatible parser generator
sug: flex fast lexical analyzer generator
sug: gcc-doc Пакет недоступен
sug: gdb-x86-64-linux-gnu Пакет недоступен
sug: libtool Сценарий сопровождения общих библиотек
sug: make утилита управления компиляцией
sug: manpages-dev Manual pages about using GNU/Linux for development
Загрузка gcc-x86-64-linux-gnu
Загрузить для всех доступных архитектур
Архитектура
Размер пакета
В установленном виде
Файлы
arm64
1,4 Кб
24,0 Кб
[список файлов]
i386
1,4 Кб
24,0 Кб
[список файлов]
ppc64el
1,4 Кб
24,0 Кб
[список файлов]
Эта страница также доступна на следующих языках (Как установить язык по умолчанию):
Чтобы сообщить о проблеме, связанной с веб-сайтом, отправьте сообщение (на английском) в список рассылки debian-www@lists.debian.org. Прочую контактную информацию см. на странице Debian Как с нами связаться.
) GNU C Library: Development Libraries and Header Files (for cross-compiling)
sug: gcc-10-doc (>= 10) documentation for the GNU compilers (gcc, gobjc, g++)
sug: gcc-10-locales (>= 10) GCC, the GNU compiler collection (native language support files)
sug: gcc-10-multilib-x86-64-linux-gnu GNU C compiler (multilib support) (cross compiler for amd64 architecture)
Загрузка gcc-10-x86-64-linux-gnu
Загрузить для всех доступных архитектур
Архитектура
Версия
Размер пакета
В установленном виде
Файлы
arm64
10.3.0-8cross1
51 058,5 Кб
233 312,0 Кб
[список файлов]
i386
10.3.0-8cross1
50 720,3 Кб
190 745,0 Кб
[список файлов]
ppc64el
10.3.0-8cross1
53 664,4 Кб
254 036,0 Кб
[список файлов]
x32 (неофициальный перенос)
10.3.0-9cross1
51 417,5 Кб
189 028,0 Кб
[список файлов]
Эта страница также доступна на следующих языках (Как установить язык по умолчанию):
Чтобы сообщить о проблеме, связанной с веб-сайтом, отправьте сообщение (на английском) в список рассылки debian-www@lists.debian.org. Прочую контактную информацию см. на странице Debian Как с нами связаться.
Это руководство является свободным программным обеспечением; вы можете его распространять и/или модифицировать на условиях Стандартной Общественной Лицензии GNU. С текстом соглашения можно ознакомиться здесь: Приложение F, GNU General Public License.
Данный документ содержит инструкции по установке системы Debian GNU/Linux 9 ( « stretch » ) для архитектуры 64-bit PC ( « amd64 » ). Кроме того, в нём указаны источники более подробной информации и описаны методы наиболее эффективного применения системы Debian.
Примечание
Несмотря на то, что данное руководство по установке на amd64 полностью соответствует текущей программе установки, планируется внести некоторые изменения и провести реорганизацию документа после официального выпуска stretch. Свежую версию этого руководства можно найти в Интернете на домашней странице debian-installer . Там же находятся дополнительные переводы руководства.
Предупреждение
This translation of the installation guide is not up-to-date and currently there is noone actively working on updating it. Keep this in mind when reading it; it may contain outdated or wrong information. Read or double-check the English variant, if in doubt. If you can help us with updating the translation, please contact or the debian-l10n-xxx mailinglist for this language. Many thanks
Источник
SYNOPSIS¶
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 man page does not describe the command language; see the ld entry in «info» for full details on the command language and on other aspects of the GNU linker.
This version of ld uses the general purpose BFD libraries to operate on object files. This allows ld to read, combine, and write object files in many different formats—for example, COFF or «a.out» . Different formats may be linked together to produce any available kind of object file.
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.
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 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. 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.
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 equivalent. 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 passing 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.
-akeyword 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. —auditAUDITLIB Adds AUDITLIB to the «DT_AUDIT» entry of the dynamic section. AUDITLIB is not checked for existence, nor will it use the DT_SONAME specified in the library. If specified multiple times «DT_AUDIT» 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 «DT_DEPAUDIT» entry in the output file. This option is only meaningful on ELF platforms supporting the rtld-audit interface. -Aarchitecture—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 particular architecture in the 960 family, enabling some safeguards and modifying the archive-library search path.
Future releases of ld may support similar functionality for other architecture families.
-binput-format—format=input-formatld 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.)
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 -binput-format before each group of object files in a particular format.
The default format is taken from the environment variable «GNUTARGET» .
You can also define the input format from a script, using the command «TARGET» ;
-cMRI-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 the MRI Compatible Script Files section of GNU ld documentation. 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 «FORCE_COMMON_ALLOCATION» has the same effect. —depauditAUDITLIB-PAUDITLIB Adds AUDITLIB to the «DT_DEPAUDIT» entry of the dynamic section. AUDITLIB is not checked for existence, nor will it use the DT_SONAME specified in the library. If specified multiple times «DT_DEPAUDIT» 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. -eentry—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). —exclude-libslib,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 .def 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-implibmodule,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 input 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 .def 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. -fname—auxiliary=name When creating an ELF shared object, set the internal DT_AUXILIARY 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 DT_AUXILIARY 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 DT_AUXILIARY entries will be created in the order in which they appear on the command line.
-Fname—filter=name When creating an ELF shared object, set the internal DT_FILTER 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 DT_FILTER 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.
-fini=name When creating an ELF executable or shared object, call NAME when the executable or shared object is unloaded, by setting DT_FINI 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. -Gvalue—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 small objects into different sections. This is ignored for other object file formats. -hname-soname=name When creating an ELF shared object, set the internal DT_SONAME field to the specified name. When an executable is linked with a shared object which has a DT_SONAME field, then when the executable is run the dynamic linker will attempt to load the shared object specified by the DT_SONAME 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 DT_INIT to the address of the function. By default, the linker uses «_init» as the function to call. -lnamespec—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 the library path for a file called libnamespec.a.
On systems which support shared libraries, ld may also search for files other than libnamespec.a. Specifically, on ELF and SunOS systems, ld will search a directory for a library called libnamespec.so before searching for one called libnamespec.a. (By convention, a «.so» 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.
-Lsearchdir—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 «=» or $SYSROOT , then this prefix 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.
The paths can also be specified in a link script with the «SEARCH_DIR» command. Directories specified this way are searched at the point in which the linker script appears in the command line.
-memulation 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 the 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.
Note that the location of the compiler originated plugins is different from the place where the ar, nm and ranlib programs search for their plugins. In order for those commands to make use of a compiler based plugin it must first be copied into the $/bfd-plugins directory. All gcc based linker plugins are backward compatible, so it is sufficient to just copy in the newest one.
—push-state The —push-state allows to preserve the current 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, -call_shared, -non_shared, -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:
—pop-state 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-dynamic 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 partiallinking. 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 «a.out» -based formats do not support partial linking with input files in other formats at all.
This option does the same thing as -i.
-Rfilename—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. —strip-discarded—no-strip-discarded Omit (or do not omit) global symbols defined in discarded sections. Enabled by default. -t—trace Print the names of the input files as ld processes them. -Tscriptfile—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. 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. -dTscriptfile—default-script=scriptfile Use scriptfile as the default linker script.
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).
-usymbol—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, -Urdoes 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 script.
MODE can have any of the following values:
The default if —orphan-handling is not given is «place» .
This option is useful when you have an undefined symbol in your link but don’t know where the reference is coming from.
-Ypath Add path to the default library search path. This option exists for Solaris compatibility. -zkeyword The recognized keywords are:
Other keywords are ignored for Solaris compatibility.
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 DT_NEEDED tags for dynamic libraries mentioned on the command line after the —as-needed option. Normally the linker will add a DT_NEEDED tag for each dynamic library mentioned on the command line, regardless of whether the library is actually needed or not. —as-needed causes a DT_NEEDED 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 DT_NEEDED lists of other needed libraries, a non-weak undefined symbol reference from another needed dynamic library. Object files or libraries appearing 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. -assertkeyword This option is ignored for SunOS compatibility. -Bdynamic-dy-call_shared 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 «DF_1_GROUP» flag in the «DT_FLAGS_1» 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-non_shared-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 libraries 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 suitable 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 DT_NEEDED tags inside ELF dynamic libraries mentioned on the command line. Normally the linker won’t add a DT_NEEDED tag to the output binary for each library mentioned in a DT_NEEDED 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 DT_NEEDED 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 DT_NEEDED 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 DT_NEEDED 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 assignment of addresses to common symbols. The script command «INHIBIT_COMMON_ALLOCATION» has the same effect.
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.
—force-group-allocation This option causes the linker to place section group members like normal input sections, and to delete the section groups. This is the default behaviour for a final link but this option can be used to change the behaviour of a relocatable link (-r). The script command «FORCE_GROUP_ALLOCATION» has the same effect. —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. 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 COLLECT_NO_DEMANGLE is set. These options may be used to override the default. -Ifile—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. —embedded-relocs This option is similar to the —emit-relocs option except that the relocs are stored in a target specific section. This option is only supported by the BFIN, CR16 and M68K targets. —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 .exe suffix.
If a successfully built fully linked output file does not have a «.exe» or «.dll» suffix, this option forces the linker to copy the output file to one of the same name with a «.exe» 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 «.exe» 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 «OUTPUT_FORMAT» linker script command. —print-memory-usage Print used size, total size and used size of memory regions created with the MEMORY command. This is useful on embedded targets 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-memoryld 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 behaviour 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 link 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.
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 these 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 «LD_RUN_PATH» 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, ignoring 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 path 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:
If the required shared library is not found, the linker will issue a warning and continue with the link.
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 «.bss» , «.data» or «.text» 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:
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.
There are three kinds of global symbols, illustrated here by C examples:
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.
1. Turning a common symbol into a reference, because there is already a definition for the symbol.
2. 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.
3. Merging a common symbol with a previous same-sized common symbol.
4. Merging a common symbol with a previous larger common symbol.
5. 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.
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 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 «__wrap_malloc» instead. The call to «__real_malloc» in «__wrap_malloc» will call the real «malloc» function.
You may wish to provide a «__real_malloc» function as well, so that links without the —wrap option will succeed. If you do this, you should not put the definition of «__real_malloc» in the same file as «__wrap_malloc» ; 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 «.eh_frame_hdr» section and ELF «PT_GNU_EH_FRAME» segment header. —no-ld-generated-unwind-info Request creation of «.eh_frame» 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 «.hash» section, «gnu» for new style GNU «.gnu.hash» section or «both» for both the classic ELF «.hash» and new style GNU «.gnu.hash» 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 .zdebug instead of .debug. —compress-debug-sections=zlib-gabi also compresses DWARF debug sections, but rather than renaming them it sets the SHF_COMPRESSED 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 default 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 «.note.gnu.build-id» ELF note section or a «.buildid» 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 hash 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.
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 «*.dll» when you use this option. In addition, the linker fully supports the standard «*.def» files, which may be specified 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-filefile 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 «.def» 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 technically 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 mismatches 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 «impure_ptr» 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: «_cygwin_dll_entry@12» , «_cygwin_crt0_common@8» , «_cygwin_noncygwin_dll_entry@12» , «_fmode» , «_impure_ptr» , «cygwin_attach_dll» , «cygwin_premain0» , «cygwin_premain1» , «cygwin_premain2» , «cygwin_premain3» , and «environ» . [This option is specific to the i386 PE targeted port of the linker] —exclude-symbolssymbol,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] —heapreserve—heapreserve,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-basevalue 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 linker] —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 BOOT.INI. 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-versionvalue 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-versionvalue 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-versionvalue 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-versionvalue 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-versionvalue 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-versionvalue 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-deffile 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 «*.def» ) 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 port 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-prefixstring When linking dynamically to a dll without an import library, search for » .dll» in preference to «lib .dll» . 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 «__imp__symbol» 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 .rdata section to be placed into the .data section instead. This is in order to work around a problem with consts that is described here: http://www.cygwin.com/ml/cygwin/2004-09/msg01101.html
Using ‘auto-import’ generally will ‘just work’ — but sometimes you may see this message:
«variable ‘ ‘ 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. set_foo() and get_foo() 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 «__imp__symbol» 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 linker] —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] —stackreserve—stackreserve,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] —subsystemwhich—subsystemwhich:major—subsystemwhich: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-entropy-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 slightly 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.
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-sizesize 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-indexindex 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 «R_C6000_DSBT_INDEX» relocs are copied into the output file.
The —no-merge-exidx-entries switch disables the merging of adjacent exidx entries in frame unwind info.
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-windowname 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.
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 more information refer to the Info entry for ld.
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 «JALX» 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.
ENVIRONMENT¶
You can change the behaviour of ld with the environment variables «GNUTARGET» , «LDEMULATION» and «COLLECT_NO_DEMANGLE» .
«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. 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 each 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.
Normally, the linker will default to demangling symbols. However, if «COLLECT_NO_DEMANGLE» is set in the environment, then it will default to not demangling symbols. This environment variable is used in a similar fashion by the «gcc» linker wrapper program. The default may be overridden by the —demangle and —no-demangle options.
SEE ALSO¶
COPYRIGHT¶
Copyright (c) 1991-2017 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled «GNU Free Documentation License».
