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1 Installing the GNU C Library
2 ****************************
3
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
7 installation.
8
9 You will need recent versions of several GNU tools: definitely GCC
10 and GNU Make, and possibly others. *Note Tools for Compilation::,
11 below.
12
13 Configuring and compiling the GNU C Library
14 ===========================================
15
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.
22
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
25
26 $ ../glibc-VERSION/configure ARGS...
27
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.
31
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)
37 for GNU/Hurd systems.
38
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:
49
50 $ ../glibc-VERSION/configure CC="gcc -m32" CFLAGS="-O3"
51
52 The following list describes all of the available options for
53 'configure':
54
55 '--prefix=DIRECTORY'
56 Install machine-independent data files in subdirectories of
57 'DIRECTORY'. The default is to install in '/usr/local'.
58
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.
63
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.
70
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'.
76
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.
83
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.
92
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
107 metadata only).
108
109 '--disable-shared'
110 Don't build shared libraries even if it is possible. Not all
111 systems support shared libraries; you need ELF support and
112 (currently) the GNU linker.
113
114 '--enable-static-pie'
115 Enable static position independent executable (static PIE) support.
116 Static PIE is similar to static executable, but can be loaded at
117 any address without help from a dynamic linker. All static
118 programs as well as static tests are built as static PIE, except
119 for those marked with no-pie. The resulting glibc can be used with
120 the GCC option, -static-pie, which is available with GCC 8 or
121 above, to create static PIE. This option also implies that glibc
122 programs and tests are created as dynamic position independent
123 executables (PIE) by default.
124
125 '--enable-cet'
126 '--enable-cet=permissive'
127 Enable Intel Control-flow Enforcement Technology (CET) support.
128 When the GNU C Library is built with '--enable-cet' or
129 '--enable-cet=permissive', the resulting library is protected with
130 indirect branch tracking (IBT) and shadow stack (SHSTK). When CET
131 is enabled, the GNU C Library is compatible with all existing
132 executables and shared libraries. This feature is currently
133 supported on i386, x86_64 and x32 with GCC 8 and binutils 2.29 or
134 later. Note that when CET is enabled, the GNU C Library requires
135 CPUs capable of multi-byte NOPs, like x86-64 processors as well as
136 Intel Pentium Pro or newer. With '--enable-cet', it is an error to
137 dlopen a non CET enabled shared library in CET enabled application.
138 With '--enable-cet=permissive', CET is disabled when dlopening a
139 non CET enabled shared library in CET enabled application.
140
141 NOTE: '--enable-cet' has been tested for i686, x86_64 and x32 on
142 non-CET processors. '--enable-cet' has been tested for i686,
143 x86_64 and x32 on CET processors.
144
145 '--disable-profile'
146 Don't build libraries with profiling information. You may want to
147 use this option if you don't plan to do profiling.
148
149 '--enable-static-nss'
150 Compile static versions of the NSS (Name Service Switch) libraries.
151 This is not recommended because it defeats the purpose of NSS; a
152 program linked statically with the NSS libraries cannot be
153 dynamically reconfigured to use a different name database.
154
155 '--enable-hardcoded-path-in-tests'
156 By default, dynamic tests are linked to run with the installed C
157 library. This option hardcodes the newly built C library path in
158 dynamic tests so that they can be invoked directly.
159
160 '--disable-timezone-tools'
161 By default, timezone related utilities ('zic', 'zdump', and
162 'tzselect') are installed with the GNU C Library. If you are
163 building these independently (e.g. by using the 'tzcode' package),
164 then this option will allow disabling the install of these.
165
166 Note that you need to make sure the external tools are kept in sync
167 with the versions that the GNU C Library expects as the data
168 formats may change over time. Consult the 'timezone' subdirectory
169 for more details.
170
171 '--enable-stack-protector'
172 '--enable-stack-protector=strong'
173 '--enable-stack-protector=all'
174 Compile the C library and all other parts of the glibc package
175 (including the threading and math libraries, NSS modules, and
176 transliteration modules) using the GCC '-fstack-protector',
177 '-fstack-protector-strong' or '-fstack-protector-all' options to
178 detect stack overruns. Only the dynamic linker and a small number
179 of routines called directly from assembler are excluded from this
180 protection.
181
182 '--enable-bind-now'
183 Disable lazy binding for installed shared objects and programs.
184 This provides additional security hardening because it enables full
185 RELRO and a read-only global offset table (GOT), at the cost of
186 slightly increased program load times.
187
188 '--enable-pt_chown'
189 The file 'pt_chown' is a helper binary for 'grantpt' (*note
190 Pseudo-Terminals: Allocation.) that is installed setuid root to fix
191 up pseudo-terminal ownership. It is not built by default because
192 systems using the Linux kernel are commonly built with the 'devpts'
193 filesystem enabled and mounted at '/dev/pts', which manages
194 pseudo-terminal ownership automatically. By using
195 '--enable-pt_chown', you may build 'pt_chown' and install it setuid
196 and owned by 'root'. The use of 'pt_chown' introduces additional
197 security risks to the system and you should enable it only if you
198 understand and accept those risks.
199
200 '--disable-werror'
201 By default, the GNU C Library is built with '-Werror'. If you wish
202 to build without this option (for example, if building with a newer
203 version of GCC than this version of the GNU C Library was tested
204 with, so new warnings cause the build with '-Werror' to fail), you
205 can configure with '--disable-werror'.
206
207 '--disable-mathvec'
208 By default for x86_64, the GNU C Library is built with the vector
209 math library. Use this option to disable the vector math library.
210
211 '--enable-tunables'
212 Tunables support allows additional library parameters to be
213 customized at runtime. This feature is enabled by default. This
214 option can take the following values:
215
216 'yes'
217 This is the default if no option is passed to configure. This
218 enables tunables and selects the default frontend (currently
219 'valstring').
220
221 'no'
222 This option disables tunables.
223
224 'valstring'
225 This enables tunables and selects the 'valstring' frontend for
226 tunables. This frontend allows users to specify tunables as a
227 colon-separated list in a single environment variable
228 'GLIBC_TUNABLES'.
229
230 '--disable-crypt'
231 Do not install the passphrase-hashing library 'libcrypt' or the
232 header file 'crypt.h'. 'unistd.h' will still declare the function
233 'crypt'. Using this option does not change the set of programs
234 that may need to be linked with '-lcrypt'; it only means that the
235 GNU C Library will not provide that library.
236
237 This option is for hackers and distributions experimenting with
238 independently-maintained implementations of libcrypt. It may
239 become the default in a future release.
240
241 '--disable-experimental-malloc'
242 By default, a per-thread cache is enabled in 'malloc'. While this
243 cache can be disabled on a per-application basis using tunables
244 (set glibc.malloc.tcache_count to zero), this option can be used to
245 remove it from the build completely.
246
247 '--build=BUILD-SYSTEM'
248 '--host=HOST-SYSTEM'
249 These options are for cross-compiling. If you specify both options
250 and BUILD-SYSTEM is different from HOST-SYSTEM, 'configure' will
251 prepare to cross-compile the GNU C Library from BUILD-SYSTEM to be
252 used on HOST-SYSTEM. You'll probably need the '--with-headers'
253 option too, and you may have to override CONFIGURE's selection of
254 the compiler and/or binutils.
255
256 If you only specify '--host', 'configure' will prepare for a native
257 compile but use what you specify instead of guessing what your
258 system is. This is most useful to change the CPU submodel. For
259 example, if 'configure' guesses your machine as 'i686-pc-linux-gnu'
260 but you want to compile a library for 586es, give
261 '--host=i586-pc-linux-gnu' or just '--host=i586-linux' and add the
262 appropriate compiler flags ('-mcpu=i586' will do the trick) to
263 'CC'.
264
265 If you specify just '--build', 'configure' will get confused.
266
267 '--with-pkgversion=VERSION'
268 Specify a description, possibly including a build number or build
269 date, of the binaries being built, to be included in '--version'
270 output from programs installed with the GNU C Library. For
271 example, '--with-pkgversion='FooBar GNU/Linux glibc build 123''.
272 The default value is 'GNU libc'.
273
274 '--with-bugurl=URL'
275 Specify the URL that users should visit if they wish to report a
276 bug, to be included in '--help' output from programs installed with
277 the GNU C Library. The default value refers to the main
278 bug-reporting information for the GNU C Library.
279
280 To build the library and related programs, type 'make'. This will
281 produce a lot of output, some of which may look like errors from 'make'
282 but aren't. Look for error messages from 'make' containing '***'.
283 Those indicate that something is seriously wrong.
284
285 The compilation process can take a long time, depending on the
286 configuration and the speed of your machine. Some complex modules may
287 take a very long time to compile, as much as several minutes on slower
288 machines. Do not panic if the compiler appears to hang.
289
290 If you want to run a parallel make, simply pass the '-j' option with
291 an appropriate numeric parameter to 'make'. You need a recent GNU
292 'make' version, though.
293
294 To build and run test programs which exercise some of the library
295 facilities, type 'make check'. If it does not complete successfully, do
296 not use the built library, and report a bug after verifying that the
297 problem is not already known. *Note Reporting Bugs::, for instructions
298 on reporting bugs. Note that some of the tests assume they are not
299 being run by 'root'. We recommend you compile and test the GNU C
300 Library as an unprivileged user.
301
302 Before reporting bugs make sure there is no problem with your system.
303 The tests (and later installation) use some pre-existing files of the
304 system such as '/etc/passwd', '/etc/nsswitch.conf' and others. These
305 files must all contain correct and sensible content.
306
307 Normally, 'make check' will run all the tests before reporting all
308 problems found and exiting with error status if any problems occurred.
309 You can specify 'stop-on-test-failure=y' when running 'make check' to
310 make the test run stop and exit with an error status immediately when a
311 failure occurs.
312
313 To format the 'GNU C Library Reference Manual' for printing, type
314 'make dvi'. You need a working TeX installation to do this. The
315 distribution builds the on-line formatted version of the manual, as Info
316 files, as part of the build process. You can build them manually with
317 'make info'.
318
319 The library has a number of special-purpose configuration parameters
320 which you can find in 'Makeconfig'. These can be overwritten with the
321 file 'configparms'. To change them, create a 'configparms' in your
322 build directory and add values as appropriate for your system. The file
323 is included and parsed by 'make' and has to follow the conventions for
324 makefiles.
325
326 It is easy to configure the GNU C Library for cross-compilation by
327 setting a few variables in 'configparms'. Set 'CC' to the
328 cross-compiler for the target you configured the library for; it is
329 important to use this same 'CC' value when running 'configure', like
330 this: 'configure TARGET CC=TARGET-gcc'. Set 'BUILD_CC' to the compiler
331 to use for programs run on the build system as part of compiling the
332 library. You may need to set 'AR' to cross-compiling versions of 'ar'
333 if the native tools are not configured to work with object files for the
334 target you configured for. When cross-compiling the GNU C Library, it
335 may be tested using 'make check
336 test-wrapper="SRCDIR/scripts/cross-test-ssh.sh HOSTNAME"', where SRCDIR
337 is the absolute directory name for the main source directory and
338 HOSTNAME is the host name of a system that can run the newly built
339 binaries of the GNU C Library. The source and build directories must be
340 visible at the same locations on both the build system and HOSTNAME.
341
342 In general, when testing the GNU C Library, 'test-wrapper' may be set
343 to the name and arguments of any program to run newly built binaries.
344 This program must preserve the arguments to the binary being run, its
345 working directory and the standard input, output and error file
346 descriptors. If 'TEST-WRAPPER env' will not work to run a program with
347 environment variables set, then 'test-wrapper-env' must be set to a
348 program that runs a newly built program with environment variable
349 assignments in effect, those assignments being specified as 'VAR=VALUE'
350 before the name of the program to be run. If multiple assignments to
351 the same variable are specified, the last assignment specified must take
352 precedence. Similarly, if 'TEST-WRAPPER env -i' will not work to run a
353 program with an environment completely empty of variables except those
354 directly assigned, then 'test-wrapper-env-only' must be set; its use has
355 the same syntax as 'test-wrapper-env', the only difference in its
356 semantics being starting with an empty set of environment variables
357 rather than the ambient set.
358
359 Installing the C Library
360 ========================
361
362 To install the library and its header files, and the Info files of the
363 manual, type 'make install'. This will build things, if necessary,
364 before installing them; however, you should still compile everything
365 first. If you are installing the GNU C Library as your primary C
366 library, we recommend that you shut the system down to single-user mode
367 first, and reboot afterward. This minimizes the risk of breaking things
368 when the library changes out from underneath.
369
370 'make install' will do the entire job of upgrading from a previous
371 installation of the GNU C Library version 2.x. There may sometimes be
372 headers left behind from the previous installation, but those are
373 generally harmless. If you want to avoid leaving headers behind you can
374 do things in the following order.
375
376 You must first build the library ('make'), optionally check it ('make
377 check'), switch the include directories and then install ('make
378 install'). The steps must be done in this order. Not moving the
379 directory before install will result in an unusable mixture of header
380 files from both libraries, but configuring, building, and checking the
381 library requires the ability to compile and run programs against the old
382 library. The new '/usr/include', after switching the include
383 directories and before installing the library should contain the Linux
384 headers, but nothing else. If you do this, you will need to restore any
385 headers from libraries other than the GNU C Library yourself after
386 installing the library.
387
388 You can install the GNU C Library somewhere other than where you
389 configured it to go by setting the 'DESTDIR' GNU standard make variable
390 on the command line for 'make install'. The value of this variable is
391 prepended to all the paths for installation. This is useful when
392 setting up a chroot environment or preparing a binary distribution. The
393 directory should be specified with an absolute file name. Installing
394 with the 'prefix' and 'exec_prefix' GNU standard make variables set is
395 not supported.
396
397 The GNU C Library includes a daemon called 'nscd', which you may or
398 may not want to run. 'nscd' caches name service lookups; it can
399 dramatically improve performance with NIS+, and may help with DNS as
400 well.
401
402 One auxiliary program, '/usr/libexec/pt_chown', is installed setuid
403 'root' if the '--enable-pt_chown' configuration option is used. This
404 program is invoked by the 'grantpt' function; it sets the permissions on
405 a pseudoterminal so it can be used by the calling process. If you are
406 using a Linux kernel with the 'devpts' filesystem enabled and mounted at
407 '/dev/pts', you don't need this program.
408
409 After installation you should configure the timezone and install
410 locales for your system. The time zone configuration ensures that your
411 system time matches the time for your current timezone. The locales
412 ensure that the display of information on your system matches the
413 expectations of your language and geographic region.
414
415 The GNU C Library is able to use two kinds of localization
416 information sources, the first is a locale database named
417 'locale-archive' which is generally installed as
418 '/usr/lib/locale/locale-archive'. The locale archive has the benefit of
419 taking up less space and being very fast to load, but only if you plan
420 to install sixty or more locales. If you plan to install one or two
421 locales you can instead install individual locales into their self-named
422 directories e.g. '/usr/lib/locale/en_US.utf8'. For example to install
423 the German locale using the character set for UTF-8 with name 'de_DE'
424 into the locale archive issue the command 'localedef -i de_DE -f UTF-8
425 de_DE', and to install just the one locale issue the command 'localedef
426 --no-archive -i de_DE -f UTF-8 de_DE'. To configure all locales that
427 are supported by the GNU C Library, you can issue from your build
428 directory the command 'make localedata/install-locales' to install all
429 locales into the locale archive or 'make
430 localedata/install-locale-files' to install all locales as files in the
431 default configured locale installation directory (derived from
432 '--prefix' or '--localedir'). To install into an alternative system
433 root use 'DESTDIR' e.g. 'make localedata/install-locale-files
434 DESTDIR=/opt/glibc', but note that this does not change the configured
435 prefix.
436
437 To configure the locally used timezone, set the 'TZ' environment
438 variable. The script 'tzselect' helps you to select the right value.
439 As an example, for Germany, 'tzselect' would tell you to use
440 'TZ='Europe/Berlin''. For a system wide installation (the given paths
441 are for an installation with '--prefix=/usr'), link the timezone file
442 which is in '/usr/share/zoneinfo' to the file '/etc/localtime'. For
443 Germany, you might execute 'ln -s /usr/share/zoneinfo/Europe/Berlin
444 /etc/localtime'.
445
446 Recommended Tools for Compilation
447 =================================
448
449 We recommend installing the following GNU tools before attempting to
450 build the GNU C Library:
451
452 * GNU 'make' 4.0 or newer
453
454 As of relase time, GNU 'make' 4.2.1 is the newest verified to work
455 to build the GNU C Library.
456
457 * GCC 6.2 or newer
458
459 GCC 6.2 or higher is required. In general it is recommended to use
460 the newest version of the compiler that is known to work for
461 building the GNU C Library, as newer compilers usually produce
462 better code. As of release time, GCC 9.2.1 is the newest compiler
463 verified to work to build the GNU C Library.
464
465 For PowerPC 64-bits little-endian (powerpc64le), a GCC version with
466 support for '-mno-gnu-attribute', '-mabi=ieeelongdouble', and
467 '-mabi=ibmlondouble' is required. Likewise, the compiler must also
468 support passing '-mlong-double-128' with the preceding options. As
469 of release, this implies GCC 7.4 and newer (excepting GCC 7.5.0,
470 see GCC PR94200). These additional features are required for
471 building the GNU C Library with support for IEEE long double.
472
473 For ARC architecture builds, GCC 8.3 or higher is needed.
474
475 For multi-arch support it is recommended to use a GCC which has
476 been built with support for GNU indirect functions. This ensures
477 that correct debugging information is generated for functions
478 selected by IFUNC resolvers. This support can either be enabled by
479 configuring GCC with '--enable-gnu-indirect-function', or by
480 enabling it by default by setting 'default_gnu_indirect_function'
481 variable for a particular architecture in the GCC source file
482 'gcc/config.gcc'.
483
484 You can use whatever compiler you like to compile programs that use
485 the GNU C Library.
486
487 Check the FAQ for any special compiler issues on particular
488 platforms.
489
490 * GNU 'binutils' 2.25 or later
491
492 You must use GNU 'binutils' (as and ld) to build the GNU C Library.
493 No other assembler or linker has the necessary functionality at the
494 moment. As of release time, GNU 'binutils' 2.32 is the newest
495 verified to work to build the GNU C Library.
496
497 For PowerPC 64-bits little-endian (powerpc64le), 'objcopy' is
498 required to support '--update-section'. This option requires
499 binutils 2.26 or newer.
500
501 ARC architecture needs 'binutils' 2.32 or higher for TLS related
502 fixes.
503
504 * GNU 'texinfo' 4.7 or later
505
506 To correctly translate and install the Texinfo documentation you
507 need this version of the 'texinfo' package. Earlier versions do
508 not understand all the tags used in the document, and the
509 installation mechanism for the info files is not present or works
510 differently. As of release time, 'texinfo' 6.6 is the newest
511 verified to work to build the GNU C Library.
512
513 * GNU 'awk' 3.1.2, or higher
514
515 'awk' is used in several places to generate files. Some 'gawk'
516 extensions are used, including the 'asorti' function, which was
517 introduced in version 3.1.2 of 'gawk'. As of release time, 'gawk'
518 version 5.0.1 is the newest verified to work to build the GNU C
519 Library.
520
521 * GNU 'bison' 2.7 or later
522
523 'bison' is used to generate the 'yacc' parser code in the 'intl'
524 subdirectory. As of release time, 'bison' version 3.4.1 is the
525 newest verified to work to build the GNU C Library.
526
527 * Perl 5
528
529 Perl is not required, but if present it is used in some tests and
530 the 'mtrace' program, to build the GNU C Library manual. As of
531 release time 'perl' version 5.30.1 is the newest verified to work
532 to build the GNU C Library.
533
534 * GNU 'sed' 3.02 or newer
535
536 'Sed' is used in several places to generate files. Most scripts
537 work with any version of 'sed'. As of release time, 'sed' version
538 4.5 is the newest verified to work to build the GNU C Library.
539
540 * Python 3.4 or later
541
542 Python is required to build the GNU C Library. As of release time,
543 Python 3.7.4 is the newest verified to work for building and
544 testing the GNU C Library.
545
546 * PExpect 4.0
547
548 The pretty printer tests drive GDB through test programs and
549 compare its output to the printers'. PExpect is used to capture
550 the output of GDB, and should be compatible with the Python version
551 in your system. As of release time PExpect 4.3 is the newest
552 verified to work to test the pretty printers.
553
554 * GDB 7.8 or later with support for Python 2.7/3.4 or later
555
556 GDB itself needs to be configured with Python support in order to
557 use the pretty printers. Notice that your system having Python
558 available doesn't imply that GDB supports it, nor that your
559 system's Python and GDB's have the same version. As of release
560 time GNU 'debugger' 8.3 is the newest verified to work to test the
561 pretty printers.
562
563 Unless Python, PExpect and GDB with Python support are present, the
564 printer tests will report themselves as 'UNSUPPORTED'. Notice that
565 some of the printer tests require the GNU C Library to be compiled
566 with debugging symbols.
567
568 If you change any of the 'configure.ac' files you will also need
569
570 * GNU 'autoconf' 2.69 (exactly)
571
572 and if you change any of the message translation files you will need
573
574 * GNU 'gettext' 0.10.36 or later
575
576 As of release time, GNU 'gettext' version 0.19.8.1 is the newest
577 version verified to work to build the GNU C Library.
578
579 You may also need these packages if you upgrade your source tree using
580 patches, although we try to avoid this.
581
582 Specific advice for GNU/Linux systems
583 =====================================
584
585 If you are installing the GNU C Library on GNU/Linux systems, you need
586 to have the header files from a 3.2 or newer kernel around for
587 reference. (For the ia64 architecture, you need version 3.2.18 or newer
588 because this is the first version with support for the 'accept4' system
589 call.) These headers must be installed using 'make headers_install';
590 the headers present in the kernel source directory are not suitable for
591 direct use by the GNU C Library. You do not need to use that kernel,
592 just have its headers installed where the GNU C Library can access them,
593 referred to here as INSTALL-DIRECTORY. The easiest way to do this is to
594 unpack it in a directory such as '/usr/src/linux-VERSION'. In that
595 directory, run 'make headers_install
596 INSTALL_HDR_PATH=INSTALL-DIRECTORY'. Finally, configure the GNU C
597 Library with the option '--with-headers=INSTALL-DIRECTORY/include'. Use
598 the most recent kernel you can get your hands on. (If you are
599 cross-compiling the GNU C Library, you need to specify
600 'ARCH=ARCHITECTURE' in the 'make headers_install' command, where
601 ARCHITECTURE is the architecture name used by the Linux kernel, such as
602 'x86' or 'powerpc'.)
603
604 After installing the GNU C Library, you may need to remove or rename
605 directories such as '/usr/include/linux' and '/usr/include/asm', and
606 replace them with copies of directories such as 'linux' and 'asm' from
607 'INSTALL-DIRECTORY/include'. All directories present in
608 'INSTALL-DIRECTORY/include' should be copied, except that the GNU C
609 Library provides its own version of '/usr/include/scsi'; the files
610 provided by the kernel should be copied without replacing those provided
611 by the GNU C Library. The 'linux', 'asm' and 'asm-generic' directories
612 are required to compile programs using the GNU C Library; the other
613 directories describe interfaces to the kernel but are not required if
614 not compiling programs using those interfaces. You do not need to copy
615 kernel headers if you did not specify an alternate kernel header source
616 using '--with-headers'.
617
618 The Filesystem Hierarchy Standard for GNU/Linux systems expects some
619 components of the GNU C Library installation to be in '/lib' and some in
620 '/usr/lib'. This is handled automatically if you configure the GNU C
621 Library with '--prefix=/usr'. If you set some other prefix or allow it
622 to default to '/usr/local', then all the components are installed there.
623
624 Reporting Bugs
625 ==============
626
627 There are probably bugs in the GNU C Library. There are certainly
628 errors and omissions in this manual. If you report them, they will get
629 fixed. If you don't, no one will ever know about them and they will
630 remain unfixed for all eternity, if not longer.
631
632 It is a good idea to verify that the problem has not already been
633 reported. Bugs are documented in two places: The file 'BUGS' describes
634 a number of well known bugs and the central GNU C Library bug tracking
635 system has a WWW interface at <https://sourceware.org/bugzilla/>. The
636 WWW interface gives you access to open and closed reports. A closed
637 report normally includes a patch or a hint on solving the problem.
638
639 To report a bug, first you must find it. With any luck, this will be
640 the hard part. Once you've found a bug, make sure it's really a bug. A
641 good way to do this is to see if the GNU C Library behaves the same way
642 some other C library does. If so, probably you are wrong and the
643 libraries are right (but not necessarily). If not, one of the libraries
644 is probably wrong. It might not be the GNU C Library. Many historical
645 Unix C libraries permit things that we don't, such as closing a file
646 twice.
647
648 If you think you have found some way in which the GNU C Library does
649 not conform to the ISO and POSIX standards (*note Standards and
650 Portability::), that is definitely a bug. Report it!
651
652 Once you're sure you've found a bug, try to narrow it down to the
653 smallest test case that reproduces the problem. In the case of a C
654 library, you really only need to narrow it down to one library function
655 call, if possible. This should not be too difficult.
656
657 The final step when you have a simple test case is to report the bug.
658 Do this at <https://www.gnu.org/software/libc/bugs.html>.
659
660 If you are not sure how a function should behave, and this manual
661 doesn't tell you, that's a bug in the manual. Report that too! If the
662 function's behavior disagrees with the manual, then either the library
663 or the manual has a bug, so report the disagreement. If you find any
664 errors or omissions in this manual, please report them to the bug
665 database. If you refer to specific sections of the manual, please
666 include the section names for easier identification.