1 Installing the GNU C Library
2 ****************************
4 Before you do anything else, you should read the FAQ at
5 <https://sourceware.org/glibc/wiki/FAQ>. It answers common questions
6 and describes problems you may experience with compilation and
9 You will need recent versions of several GNU tools: definitely GCC
10 and GNU Make, and possibly others. *Note Tools for Compilation::,
13 Configuring and compiling the GNU C Library
14 ===========================================
16 The GNU C Library cannot be compiled in the source directory. You must
17 build it in a separate build directory. For example, if you have
18 unpacked the GNU C Library sources in '/src/gnu/glibc-VERSION', create a
19 directory '/src/gnu/glibc-build' to put the object files in. This
20 allows removing the whole build directory in case an error occurs, which
21 is the safest way to get a fresh start and should always be done.
23 From your object directory, run the shell script 'configure' located
24 at the top level of the source tree. In the scenario above, you'd type
26 $ ../glibc-VERSION/configure ARGS...
28 Please note that even though you're building in a separate build
29 directory, the compilation may need to create or modify files and
30 directories in the source directory.
32 'configure' takes many options, but the only one that is usually
33 mandatory is '--prefix'. This option tells 'configure' where you want
34 the GNU C Library installed. This defaults to '/usr/local', but the
35 normal setting to install as the standard system library is
36 '--prefix=/usr' for GNU/Linux systems and '--prefix=' (an empty prefix)
39 It may also be useful to pass 'CC=COMPILER' and 'CFLAGS=FLAGS'
40 arguments to 'configure'. 'CC' selects the C compiler that will be
41 used, and 'CFLAGS' sets optimization options for the compiler. Any
42 compiler options required for all compilations, such as options
43 selecting an ABI or a processor for which to generate code, should be
44 included in 'CC'. Options that may be overridden by the GNU C Library
45 build system for particular files, such as for optimization and
46 debugging, should go in 'CFLAGS'. The default value of 'CFLAGS' is '-g
47 -O2', and the GNU C Library cannot be compiled without optimization, so
48 if 'CFLAGS' is specified it must enable optimization. For example:
50 $ ../glibc-VERSION/configure CC="gcc -m32" CFLAGS="-O3"
52 The following list describes all of the available options for
56 Install machine-independent data files in subdirectories of
57 'DIRECTORY'. The default is to install in '/usr/local'.
59 '--exec-prefix=DIRECTORY'
60 Install the library and other machine-dependent files in
61 subdirectories of 'DIRECTORY'. The default is to the '--prefix'
62 directory if that option is specified, or '/usr/local' otherwise.
64 '--with-headers=DIRECTORY'
65 Look for kernel header files in DIRECTORY, not '/usr/include'. The
66 GNU C Library needs information from the kernel's header files
67 describing the interface to the kernel. The GNU C Library will
68 normally look in '/usr/include' for them, but if you specify this
69 option, it will look in DIRECTORY instead.
71 This option is primarily of use on a system where the headers in
72 '/usr/include' come from an older version of the GNU C Library.
73 Conflicts can occasionally happen in this case. You can also use
74 this option if you want to compile the GNU C Library with a newer
75 set of kernel headers than the ones found in '/usr/include'.
77 '--enable-kernel=VERSION'
78 This option is currently only useful on GNU/Linux systems. The
79 VERSION parameter should have the form X.Y.Z and describes the
80 smallest version of the Linux kernel the generated library is
81 expected to support. The higher the VERSION number is, the less
82 compatibility code is added, and the faster the code gets.
84 '--with-binutils=DIRECTORY'
85 Use the binutils (assembler and linker) in 'DIRECTORY', not the
86 ones the C compiler would default to. You can use this option if
87 the default binutils on your system cannot deal with all the
88 constructs in the GNU C Library. In that case, 'configure' will
89 detect the problem and suppress these constructs, so that the
90 library will still be usable, but functionality may be lost--for
91 example, you can't build a shared libc with old binutils.
93 '--with-nonshared-cflags=CFLAGS'
94 Use additional compiler flags CFLAGS to build the parts of the
95 library which are always statically linked into applications and
96 libraries even with shared linking (that is, the object files
97 contained in 'lib*_nonshared.a' libraries). The build process will
98 automatically use the appropriate flags, but this option can be
99 used to set additional flags required for building applications and
100 libraries, to match local policy. For example, if such a policy
101 requires that all code linked into applications must be built with
102 source fortification,
103 '--with-nonshared-cflags=-Wp,-D_FORTIFY_SOURCE=2' will make sure
104 that the objects in 'libc_nonshared.a' are compiled with this flag
105 (although this will not affect the generated code in this
106 particular case and potentially change debugging information and
109 '--with-timeoutfactor=NUM'
110 Specify an integer NUM to scale the timeout of test programs. This
111 factor can be changed at run time using 'TIMEOUTFACTOR' environment
115 Don't build shared libraries even if it is possible. Not all
116 systems support shared libraries; you need ELF support and
117 (currently) the GNU linker.
119 '--enable-static-pie'
120 Enable static position independent executable (static PIE) support.
121 Static PIE is similar to static executable, but can be loaded at
122 any address without help from a dynamic linker. All static
123 programs as well as static tests are built as static PIE, except
124 for those marked with no-pie. The resulting glibc can be used with
125 the GCC option, -static-pie, which is available with GCC 8 or
126 above, to create static PIE. This option also implies that glibc
127 programs and tests are created as dynamic position independent
128 executables (PIE) by default.
131 '--enable-cet=permissive'
132 Enable Intel Control-flow Enforcement Technology (CET) support.
133 When the GNU C Library is built with '--enable-cet' or
134 '--enable-cet=permissive', the resulting library is protected with
135 indirect branch tracking (IBT) and shadow stack (SHSTK). When CET
136 is enabled, the GNU C Library is compatible with all existing
137 executables and shared libraries. This feature is currently
138 supported on i386, x86_64 and x32 with GCC 8 and binutils 2.29 or
139 later. Note that when CET is enabled, the GNU C Library requires
140 CPUs capable of multi-byte NOPs, like x86-64 processors as well as
141 Intel Pentium Pro or newer. With '--enable-cet', it is an error to
142 dlopen a non CET enabled shared library in CET enabled application.
143 With '--enable-cet=permissive', CET is disabled when dlopening a
144 non CET enabled shared library in CET enabled application.
146 NOTE: '--enable-cet' has been tested for i686, x86_64 and x32 on
147 non-CET processors. '--enable-cet' has been tested for i686,
148 x86_64 and x32 on CET processors.
150 '--enable-memory-tagging'
151 Enable memory tagging support if the architecture supports it.
152 When the GNU C Library is built with this option then the resulting
153 library will be able to control the use of tagged memory when
154 hardware support is present by use of the tunable
155 'glibc.mem.tagging'. This includes the generation of tagged memory
156 when using the 'malloc' APIs.
158 At present only AArch64 platforms with MTE provide this
159 functionality, although the library will still operate (without
160 memory tagging) on older versions of the architecture.
162 The default is to disable support for memory tagging.
165 Don't build libraries with profiling information. You may want to
166 use this option if you don't plan to do profiling.
168 '--enable-static-nss'
169 Compile static versions of the NSS (Name Service Switch) libraries.
170 This is not recommended because it defeats the purpose of NSS; a
171 program linked statically with the NSS libraries cannot be
172 dynamically reconfigured to use a different name database.
174 '--enable-hardcoded-path-in-tests'
175 By default, dynamic tests are linked to run with the installed C
176 library. This option hardcodes the newly built C library path in
177 dynamic tests so that they can be invoked directly.
179 '--disable-timezone-tools'
180 By default, timezone related utilities ('zic', 'zdump', and
181 'tzselect') are installed with the GNU C Library. If you are
182 building these independently (e.g. by using the 'tzcode' package),
183 then this option will allow disabling the install of these.
185 Note that you need to make sure the external tools are kept in sync
186 with the versions that the GNU C Library expects as the data
187 formats may change over time. Consult the 'timezone' subdirectory
190 '--enable-stack-protector'
191 '--enable-stack-protector=strong'
192 '--enable-stack-protector=all'
193 Compile the C library and all other parts of the glibc package
194 (including the threading and math libraries, NSS modules, and
195 transliteration modules) using the GCC '-fstack-protector',
196 '-fstack-protector-strong' or '-fstack-protector-all' options to
197 detect stack overruns. Only the dynamic linker and a small number
198 of routines called directly from assembler are excluded from this
202 Disable lazy binding for installed shared objects and programs.
203 This provides additional security hardening because it enables full
204 RELRO and a read-only global offset table (GOT), at the cost of
205 slightly increased program load times.
208 The file 'pt_chown' is a helper binary for 'grantpt' (*note
209 Pseudo-Terminals: Allocation.) that is installed setuid root to fix
210 up pseudo-terminal ownership on GNU/Hurd. It is not required on
211 GNU/Linux, and the GNU C Library will not use the installed
212 'pt_chown' program when configured with '--enable-pt_chown'.
215 By default, the GNU C Library is built with '-Werror'. If you wish
216 to build without this option (for example, if building with a newer
217 version of GCC than this version of the GNU C Library was tested
218 with, so new warnings cause the build with '-Werror' to fail), you
219 can configure with '--disable-werror'.
222 By default for x86_64, the GNU C Library is built with the vector
223 math library. Use this option to disable the vector math library.
226 Tunables support allows additional library parameters to be
227 customized at runtime. This feature is enabled by default. This
228 option can take the following values:
231 This is the default if no option is passed to configure. This
232 enables tunables and selects the default frontend (currently
236 This option disables tunables.
239 This enables tunables and selects the 'valstring' frontend for
240 tunables. This frontend allows users to specify tunables as a
241 colon-separated list in a single environment variable
245 Do not install the passphrase-hashing library 'libcrypt' or the
246 header file 'crypt.h'. 'unistd.h' will still declare the function
247 'crypt'. Using this option does not change the set of programs
248 that may need to be linked with '-lcrypt'; it only means that the
249 GNU C Library will not provide that library.
251 This option is for hackers and distributions experimenting with
252 independently-maintained implementations of libcrypt. It may
253 become the default in a future release.
255 '--disable-experimental-malloc'
256 By default, a per-thread cache is enabled in 'malloc'. While this
257 cache can be disabled on a per-application basis using tunables
258 (set glibc.malloc.tcache_count to zero), this option can be used to
259 remove it from the build completely.
262 Disable using 'scv' instruction for syscalls. All syscalls will
263 use 'sc' instead, even if the kernel supports 'scv'. PowerPC only.
265 '--build=BUILD-SYSTEM'
267 These options are for cross-compiling. If you specify both options
268 and BUILD-SYSTEM is different from HOST-SYSTEM, 'configure' will
269 prepare to cross-compile the GNU C Library from BUILD-SYSTEM to be
270 used on HOST-SYSTEM. You'll probably need the '--with-headers'
271 option too, and you may have to override CONFIGURE's selection of
272 the compiler and/or binutils.
274 If you only specify '--host', 'configure' will prepare for a native
275 compile but use what you specify instead of guessing what your
276 system is. This is most useful to change the CPU submodel. For
277 example, if 'configure' guesses your machine as 'i686-pc-linux-gnu'
278 but you want to compile a library for 586es, give
279 '--host=i586-pc-linux-gnu' or just '--host=i586-linux' and add the
280 appropriate compiler flags ('-mcpu=i586' will do the trick) to
283 If you specify just '--build', 'configure' will get confused.
285 '--with-pkgversion=VERSION'
286 Specify a description, possibly including a build number or build
287 date, of the binaries being built, to be included in '--version'
288 output from programs installed with the GNU C Library. For
289 example, '--with-pkgversion='FooBar GNU/Linux glibc build 123''.
290 The default value is 'GNU libc'.
293 Specify the URL that users should visit if they wish to report a
294 bug, to be included in '--help' output from programs installed with
295 the GNU C Library. The default value refers to the main
296 bug-reporting information for the GNU C Library.
298 To build the library and related programs, type 'make'. This will
299 produce a lot of output, some of which may look like errors from 'make'
300 but aren't. Look for error messages from 'make' containing '***'.
301 Those indicate that something is seriously wrong.
303 The compilation process can take a long time, depending on the
304 configuration and the speed of your machine. Some complex modules may
305 take a very long time to compile, as much as several minutes on slower
306 machines. Do not panic if the compiler appears to hang.
308 If you want to run a parallel make, simply pass the '-j' option with
309 an appropriate numeric parameter to 'make'. You need a recent GNU
310 'make' version, though.
312 To build and run test programs which exercise some of the library
313 facilities, type 'make check'. If it does not complete successfully, do
314 not use the built library, and report a bug after verifying that the
315 problem is not already known. *Note Reporting Bugs::, for instructions
316 on reporting bugs. Note that some of the tests assume they are not
317 being run by 'root'. We recommend you compile and test the GNU C
318 Library as an unprivileged user.
320 Before reporting bugs make sure there is no problem with your system.
321 The tests (and later installation) use some pre-existing files of the
322 system such as '/etc/passwd', '/etc/nsswitch.conf' and others. These
323 files must all contain correct and sensible content.
325 Normally, 'make check' will run all the tests before reporting all
326 problems found and exiting with error status if any problems occurred.
327 You can specify 'stop-on-test-failure=y' when running 'make check' to
328 make the test run stop and exit with an error status immediately when a
331 To format the 'GNU C Library Reference Manual' for printing, type
332 'make dvi'. You need a working TeX installation to do this. The
333 distribution builds the on-line formatted version of the manual, as Info
334 files, as part of the build process. You can build them manually with
337 The library has a number of special-purpose configuration parameters
338 which you can find in 'Makeconfig'. These can be overwritten with the
339 file 'configparms'. To change them, create a 'configparms' in your
340 build directory and add values as appropriate for your system. The file
341 is included and parsed by 'make' and has to follow the conventions for
344 It is easy to configure the GNU C Library for cross-compilation by
345 setting a few variables in 'configparms'. Set 'CC' to the
346 cross-compiler for the target you configured the library for; it is
347 important to use this same 'CC' value when running 'configure', like
348 this: 'configure TARGET CC=TARGET-gcc'. Set 'BUILD_CC' to the compiler
349 to use for programs run on the build system as part of compiling the
350 library. You may need to set 'AR' to cross-compiling versions of 'ar'
351 if the native tools are not configured to work with object files for the
352 target you configured for. When cross-compiling the GNU C Library, it
353 may be tested using 'make check
354 test-wrapper="SRCDIR/scripts/cross-test-ssh.sh HOSTNAME"', where SRCDIR
355 is the absolute directory name for the main source directory and
356 HOSTNAME is the host name of a system that can run the newly built
357 binaries of the GNU C Library. The source and build directories must be
358 visible at the same locations on both the build system and HOSTNAME.
359 The 'cross-test-ssh.sh' script requires 'flock' from 'util-linux' to
360 work when GLIBC_TEST_ALLOW_TIME_SETTING environment variable is set.
362 It is also possible to execute tests, which require setting the date
363 on the target machine. Following use cases are supported:
364 * 'GLIBC_TEST_ALLOW_TIME_SETTING' is set in the environment in which
365 eligible tests are executed and have the privilege to run
366 'clock_settime'. In this case, nothing prevents those tests from
367 running in parallel, so the caller shall assure that those tests
368 are serialized or provide a proper wrapper script for them.
370 * The 'cross-test-ssh.sh' script is used and one passes the
371 '--allow-time-setting' flag. In this case, both sets
372 'GLIBC_TEST_ALLOW_TIME_SETTING' and serialization of test execution
373 are assured automatically.
375 In general, when testing the GNU C Library, 'test-wrapper' may be set
376 to the name and arguments of any program to run newly built binaries.
377 This program must preserve the arguments to the binary being run, its
378 working directory and the standard input, output and error file
379 descriptors. If 'TEST-WRAPPER env' will not work to run a program with
380 environment variables set, then 'test-wrapper-env' must be set to a
381 program that runs a newly built program with environment variable
382 assignments in effect, those assignments being specified as 'VAR=VALUE'
383 before the name of the program to be run. If multiple assignments to
384 the same variable are specified, the last assignment specified must take
385 precedence. Similarly, if 'TEST-WRAPPER env -i' will not work to run a
386 program with an environment completely empty of variables except those
387 directly assigned, then 'test-wrapper-env-only' must be set; its use has
388 the same syntax as 'test-wrapper-env', the only difference in its
389 semantics being starting with an empty set of environment variables
390 rather than the ambient set.
392 For AArch64 with SVE, when testing the GNU C Library, 'test-wrapper'
393 may be set to "SRCDIR/sysdeps/unix/sysv/linux/aarch64/vltest.py
394 VECTOR-LENGTH" to change Vector Length.
396 Installing the C Library
397 ========================
399 To install the library and its header files, and the Info files of the
400 manual, type 'make install'. This will build things, if necessary,
401 before installing them; however, you should still compile everything
402 first. If you are installing the GNU C Library as your primary C
403 library, we recommend that you shut the system down to single-user mode
404 first, and reboot afterward. This minimizes the risk of breaking things
405 when the library changes out from underneath.
407 'make install' will do the entire job of upgrading from a previous
408 installation of the GNU C Library version 2.x. There may sometimes be
409 headers left behind from the previous installation, but those are
410 generally harmless. If you want to avoid leaving headers behind you can
411 do things in the following order.
413 You must first build the library ('make'), optionally check it ('make
414 check'), switch the include directories and then install ('make
415 install'). The steps must be done in this order. Not moving the
416 directory before install will result in an unusable mixture of header
417 files from both libraries, but configuring, building, and checking the
418 library requires the ability to compile and run programs against the old
419 library. The new '/usr/include', after switching the include
420 directories and before installing the library should contain the Linux
421 headers, but nothing else. If you do this, you will need to restore any
422 headers from libraries other than the GNU C Library yourself after
423 installing the library.
425 You can install the GNU C Library somewhere other than where you
426 configured it to go by setting the 'DESTDIR' GNU standard make variable
427 on the command line for 'make install'. The value of this variable is
428 prepended to all the paths for installation. This is useful when
429 setting up a chroot environment or preparing a binary distribution. The
430 directory should be specified with an absolute file name. Installing
431 with the 'prefix' and 'exec_prefix' GNU standard make variables set is
434 The GNU C Library includes a daemon called 'nscd', which you may or
435 may not want to run. 'nscd' caches name service lookups; it can
436 dramatically improve performance with NIS+, and may help with DNS as
439 One auxiliary program, '/usr/libexec/pt_chown', is installed setuid
440 'root' if the '--enable-pt_chown' configuration option is used. This
441 program is invoked by the 'grantpt' function; it sets the permissions on
442 a pseudoterminal so it can be used by the calling process. If you are
443 using a Linux kernel with the 'devpts' filesystem enabled and mounted at
444 '/dev/pts', you don't need this program.
446 After installation you should configure the timezone and install
447 locales for your system. The time zone configuration ensures that your
448 system time matches the time for your current timezone. The locales
449 ensure that the display of information on your system matches the
450 expectations of your language and geographic region.
452 The GNU C Library is able to use two kinds of localization
453 information sources, the first is a locale database named
454 'locale-archive' which is generally installed as
455 '/usr/lib/locale/locale-archive'. The locale archive has the benefit of
456 taking up less space and being very fast to load, but only if you plan
457 to install sixty or more locales. If you plan to install one or two
458 locales you can instead install individual locales into their self-named
459 directories e.g. '/usr/lib/locale/en_US.utf8'. For example to install
460 the German locale using the character set for UTF-8 with name 'de_DE'
461 into the locale archive issue the command 'localedef -i de_DE -f UTF-8
462 de_DE', and to install just the one locale issue the command 'localedef
463 --no-archive -i de_DE -f UTF-8 de_DE'. To configure all locales that
464 are supported by the GNU C Library, you can issue from your build
465 directory the command 'make localedata/install-locales' to install all
466 locales into the locale archive or 'make
467 localedata/install-locale-files' to install all locales as files in the
468 default configured locale installation directory (derived from
469 '--prefix' or '--localedir'). To install into an alternative system
470 root use 'DESTDIR' e.g. 'make localedata/install-locale-files
471 DESTDIR=/opt/glibc', but note that this does not change the configured
474 To configure the locally used timezone, set the 'TZ' environment
475 variable. The script 'tzselect' helps you to select the right value.
476 As an example, for Germany, 'tzselect' would tell you to use
477 'TZ='Europe/Berlin''. For a system wide installation (the given paths
478 are for an installation with '--prefix=/usr'), link the timezone file
479 which is in '/usr/share/zoneinfo' to the file '/etc/localtime'. For
480 Germany, you might execute 'ln -s /usr/share/zoneinfo/Europe/Berlin
483 Recommended Tools for Compilation
484 =================================
486 We recommend installing the following GNU tools before attempting to
487 build the GNU C Library:
489 * GNU 'make' 4.0 or newer
491 As of relase time, GNU 'make' 4.3 is the newest verified to work to
492 build the GNU C Library.
496 GCC 6.2 or higher is required. In general it is recommended to use
497 the newest version of the compiler that is known to work for
498 building the GNU C Library, as newer compilers usually produce
499 better code. As of release time, GCC 11.2 is the newest compiler
500 verified to work to build the GNU C Library.
502 For PowerPC 64-bits little-endian (powerpc64le), a GCC version with
503 support for '-mno-gnu-attribute', '-mabi=ieeelongdouble', and
504 '-mabi=ibmlondouble' is required. Likewise, the compiler must also
505 support passing '-mlong-double-128' with the preceding options. As
506 of release, this implies GCC 7.4 and newer (excepting GCC 7.5.0,
507 see GCC PR94200). These additional features are required for
508 building the GNU C Library with support for IEEE long double.
510 For ARC architecture builds, GCC 8.3 or higher is needed.
512 For s390x architecture builds, GCC 7.1 or higher is needed (See gcc
515 For multi-arch support it is recommended to use a GCC which has
516 been built with support for GNU indirect functions. This ensures
517 that correct debugging information is generated for functions
518 selected by IFUNC resolvers. This support can either be enabled by
519 configuring GCC with '--enable-gnu-indirect-function', or by
520 enabling it by default by setting 'default_gnu_indirect_function'
521 variable for a particular architecture in the GCC source file
524 You can use whatever compiler you like to compile programs that use
527 Check the FAQ for any special compiler issues on particular
530 * GNU 'binutils' 2.25 or later
532 You must use GNU 'binutils' (as and ld) to build the GNU C Library.
533 No other assembler or linker has the necessary functionality at the
534 moment. As of release time, GNU 'binutils' 2.35.1 is the newest
535 verified to work to build the GNU C Library.
537 For PowerPC 64-bits little-endian (powerpc64le), 'objcopy' is
538 required to support '--update-section'. This option requires
539 binutils 2.26 or newer.
541 ARC architecture needs 'binutils' 2.32 or higher for TLS related
544 * GNU 'texinfo' 4.7 or later
546 To correctly translate and install the Texinfo documentation you
547 need this version of the 'texinfo' package. Earlier versions do
548 not understand all the tags used in the document, and the
549 installation mechanism for the info files is not present or works
550 differently. As of release time, 'texinfo' 6.7 is the newest
551 verified to work to build the GNU C Library.
553 * GNU 'awk' 3.1.2, or higher
555 'awk' is used in several places to generate files. Some 'gawk'
556 extensions are used, including the 'asorti' function, which was
557 introduced in version 3.1.2 of 'gawk'. As of release time, 'gawk'
558 version 5.1 is the newest verified to work to build the GNU C
561 * GNU 'bison' 2.7 or later
563 'bison' is used to generate the 'yacc' parser code in the 'intl'
564 subdirectory. As of release time, 'bison' version 3.7.4 is the
565 newest verified to work to build the GNU C Library.
569 Perl is not required, but if present it is used in some tests and
570 the 'mtrace' program, to build the GNU C Library manual. As of
571 release time 'perl' version 5.32.1 is the newest verified to work
572 to build the GNU C Library.
574 * GNU 'sed' 3.02 or newer
576 'Sed' is used in several places to generate files. Most scripts
577 work with any version of 'sed'. As of release time, 'sed' version
578 4.8 is the newest verified to work to build the GNU C Library.
580 * Python 3.4 or later
582 Python is required to build the GNU C Library. As of release time,
583 Python 3.9.6 is the newest verified to work for building and
584 testing the GNU C Library.
588 The pretty printer tests drive GDB through test programs and
589 compare its output to the printers'. PExpect is used to capture
590 the output of GDB, and should be compatible with the Python version
591 in your system. As of release time PExpect 4.8 is the newest
592 verified to work to test the pretty printers.
594 * GDB 7.8 or later with support for Python 2.7/3.4 or later
596 GDB itself needs to be configured with Python support in order to
597 use the pretty printers. Notice that your system having Python
598 available doesn't imply that GDB supports it, nor that your
599 system's Python and GDB's have the same version. As of release
600 time GNU 'debugger' 10.2 is the newest verified to work to test the
603 Unless Python, PExpect and GDB with Python support are present, the
604 printer tests will report themselves as 'UNSUPPORTED'. Notice that
605 some of the printer tests require the GNU C Library to be compiled
606 with debugging symbols.
608 If you change any of the 'configure.ac' files you will also need
610 * GNU 'autoconf' 2.69 (exactly)
612 and if you change any of the message translation files you will need
614 * GNU 'gettext' 0.10.36 or later
616 As of release time, GNU 'gettext' version 0.21 is the newest
617 version verified to work to build the GNU C Library.
619 You may also need these packages if you upgrade your source tree using
620 patches, although we try to avoid this.
622 Specific advice for GNU/Linux systems
623 =====================================
625 If you are installing the GNU C Library on GNU/Linux systems, you need
626 to have the header files from a 3.2 or newer kernel around for
627 reference. (For the ia64 architecture, you need version 3.2.18 or newer
628 because this is the first version with support for the 'accept4' system
629 call.) These headers must be installed using 'make headers_install';
630 the headers present in the kernel source directory are not suitable for
631 direct use by the GNU C Library. You do not need to use that kernel,
632 just have its headers installed where the GNU C Library can access them,
633 referred to here as INSTALL-DIRECTORY. The easiest way to do this is to
634 unpack it in a directory such as '/usr/src/linux-VERSION'. In that
635 directory, run 'make headers_install
636 INSTALL_HDR_PATH=INSTALL-DIRECTORY'. Finally, configure the GNU C
637 Library with the option '--with-headers=INSTALL-DIRECTORY/include'. Use
638 the most recent kernel you can get your hands on. (If you are
639 cross-compiling the GNU C Library, you need to specify
640 'ARCH=ARCHITECTURE' in the 'make headers_install' command, where
641 ARCHITECTURE is the architecture name used by the Linux kernel, such as
644 After installing the GNU C Library, you may need to remove or rename
645 directories such as '/usr/include/linux' and '/usr/include/asm', and
646 replace them with copies of directories such as 'linux' and 'asm' from
647 'INSTALL-DIRECTORY/include'. All directories present in
648 'INSTALL-DIRECTORY/include' should be copied, except that the GNU C
649 Library provides its own version of '/usr/include/scsi'; the files
650 provided by the kernel should be copied without replacing those provided
651 by the GNU C Library. The 'linux', 'asm' and 'asm-generic' directories
652 are required to compile programs using the GNU C Library; the other
653 directories describe interfaces to the kernel but are not required if
654 not compiling programs using those interfaces. You do not need to copy
655 kernel headers if you did not specify an alternate kernel header source
656 using '--with-headers'.
658 The Filesystem Hierarchy Standard for GNU/Linux systems expects some
659 components of the GNU C Library installation to be in '/lib' and some in
660 '/usr/lib'. This is handled automatically if you configure the GNU C
661 Library with '--prefix=/usr'. If you set some other prefix or allow it
662 to default to '/usr/local', then all the components are installed there.
667 There are probably bugs in the GNU C Library. There are certainly
668 errors and omissions in this manual. If you report them, they will get
669 fixed. If you don't, no one will ever know about them and they will
670 remain unfixed for all eternity, if not longer.
672 It is a good idea to verify that the problem has not already been
673 reported. Bugs are documented in two places: The file 'BUGS' describes
674 a number of well known bugs and the central GNU C Library bug tracking
675 system has a WWW interface at <https://sourceware.org/bugzilla/>. The
676 WWW interface gives you access to open and closed reports. A closed
677 report normally includes a patch or a hint on solving the problem.
679 To report a bug, first you must find it. With any luck, this will be
680 the hard part. Once you've found a bug, make sure it's really a bug. A
681 good way to do this is to see if the GNU C Library behaves the same way
682 some other C library does. If so, probably you are wrong and the
683 libraries are right (but not necessarily). If not, one of the libraries
684 is probably wrong. It might not be the GNU C Library. Many historical
685 Unix C libraries permit things that we don't, such as closing a file
688 If you think you have found some way in which the GNU C Library does
689 not conform to the ISO and POSIX standards (*note Standards and
690 Portability::), that is definitely a bug. Report it!
692 Once you're sure you've found a bug, try to narrow it down to the
693 smallest test case that reproduces the problem. In the case of a C
694 library, you really only need to narrow it down to one library function
695 call, if possible. This should not be too difficult.
697 The final step when you have a simple test case is to report the bug.
698 Do this at <https://www.gnu.org/software/libc/bugs.html>.
700 If you are not sure how a function should behave, and this manual
701 doesn't tell you, that's a bug in the manual. Report that too! If the
702 function's behavior disagrees with the manual, then either the library
703 or the manual has a bug, so report the disagreement. If you find any
704 errors or omissions in this manual, please report them to the bug
705 database. If you refer to specific sections of the manual, please
706 include the section names for easier identification.