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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 '--disable-shared'
94 Don't build shared libraries even if it is possible. Not all
95 systems support shared libraries; you need ELF support and
96 (currently) the GNU linker.
97
98 '--enable-static-pie'
99 Enable static position independent executable (static PIE) support.
100 Static PIE is similar to static executable, but can be loaded at
101 any address without help from a dynamic linker. All static
102 programs as well as static tests are built as static PIE, except
103 for those marked with no-pie. The resulting glibc can be used with
104 the GCC option, -static-pie, which is available with GCC 8 or
105 above, to create static PIE. This option also implies that glibc
106 programs and tests are created as dynamic position independent
107 executables (PIE) by default.
108
109 '--enable-cet'
110 Enable Intel Control-flow Enforcement Technology (CET) support.
111 When the GNU C Library is built with '--enable-cet', the resulting
112 library is protected with indirect branch tracking (IBT) and shadow
113 stack (SHSTK). When CET is enabled, the GNU C Library is
114 compatible with all existing executables and shared libraries.
115 This feature is currently supported on i386, x86_64 and x32 with
116 GCC 8 and binutils 2.29 or later. Note that when CET is enabled,
117 the GNU C Library requires CPUs capable of multi-byte NOPs, like
118 x86-64 processors as well as Intel Pentium Pro or newer.
119
120 NOTE: '--enable-cet' has been tested for i686, x86_64 and x32 on
121 non-CET processors. '--enable-cet' has been tested for x86_64 and
122 x32 on CET SDVs, but Intel CET support hasn't been validated for
123 i686.
124
125 '--disable-profile'
126 Don't build libraries with profiling information. You may want to
127 use this option if you don't plan to do profiling.
128
129 '--enable-static-nss'
130 Compile static versions of the NSS (Name Service Switch) libraries.
131 This is not recommended because it defeats the purpose of NSS; a
132 program linked statically with the NSS libraries cannot be
133 dynamically reconfigured to use a different name database.
134
135 '--enable-hardcoded-path-in-tests'
136 By default, dynamic tests are linked to run with the installed C
137 library. This option hardcodes the newly built C library path in
138 dynamic tests so that they can be invoked directly.
139
140 '--disable-timezone-tools'
141 By default, timezone related utilities ('zic', 'zdump', and
142 'tzselect') are installed with the GNU C Library. If you are
143 building these independently (e.g. by using the 'tzcode' package),
144 then this option will allow disabling the install of these.
145
146 Note that you need to make sure the external tools are kept in sync
147 with the versions that the GNU C Library expects as the data
148 formats may change over time. Consult the 'timezone' subdirectory
149 for more details.
150
151 '--enable-stack-protector'
152 '--enable-stack-protector=strong'
153 '--enable-stack-protector=all'
154 Compile the C library and all other parts of the glibc package
155 (including the threading and math libraries, NSS modules, and
156 transliteration modules) using the GCC '-fstack-protector',
157 '-fstack-protector-strong' or '-fstack-protector-all' options to
158 detect stack overruns. Only the dynamic linker and a small number
159 of routines called directly from assembler are excluded from this
160 protection.
161
162 '--enable-bind-now'
163 Disable lazy binding for installed shared objects. This provides
164 additional security hardening because it enables full RELRO and a
165 read-only global offset table (GOT), at the cost of slightly
166 increased program load times.
167
168 '--enable-pt_chown'
169 The file 'pt_chown' is a helper binary for 'grantpt' (*note
170 Pseudo-Terminals: Allocation.) that is installed setuid root to fix
171 up pseudo-terminal ownership. It is not built by default because
172 systems using the Linux kernel are commonly built with the 'devpts'
173 filesystem enabled and mounted at '/dev/pts', which manages
174 pseudo-terminal ownership automatically. By using
175 '--enable-pt_chown', you may build 'pt_chown' and install it setuid
176 and owned by 'root'. The use of 'pt_chown' introduces additional
177 security risks to the system and you should enable it only if you
178 understand and accept those risks.
179
180 '--disable-werror'
181 By default, the GNU C Library is built with '-Werror'. If you wish
182 to build without this option (for example, if building with a newer
183 version of GCC than this version of the GNU C Library was tested
184 with, so new warnings cause the build with '-Werror' to fail), you
185 can configure with '--disable-werror'.
186
187 '--disable-mathvec'
188 By default for x86_64, the GNU C Library is built with the vector
189 math library. Use this option to disable the vector math library.
190
191 '--enable-tunables'
192 Tunables support allows additional library parameters to be
193 customized at runtime. This feature is enabled by default. This
194 option can take the following values:
195
196 'yes'
197 This is the default if no option is passed to configure. This
198 enables tunables and selects the default frontend (currently
199 'valstring').
200
201 'no'
202 This option disables tunables.
203
204 'valstring'
205 This enables tunables and selects the 'valstring' frontend for
206 tunables. This frontend allows users to specify tunables as a
207 colon-separated list in a single environment variable
208 'GLIBC_TUNABLES'.
209
210 '--enable-obsolete-nsl'
211 By default, libnsl is only built as shared library for backward
212 compatibility and the NSS modules libnss_compat, libnss_nis and
213 libnss_nisplus are not built at all. Use this option to enable
214 libnsl with all depending NSS modules and header files.
215
216 '--disable-crypt'
217 Do not install the passphrase-hashing library 'libcrypt' or the
218 header file 'crypt.h'. 'unistd.h' will still declare the function
219 'crypt'. Using this option does not change the set of programs
220 that may need to be linked with '-lcrypt'; it only means that the
221 GNU C Library will not provide that library.
222
223 This option is for hackers and distributions experimenting with
224 independently-maintained implementations of libcrypt. It may
225 become the default in a future release.
226
227 '--disable-experimental-malloc'
228 By default, a per-thread cache is enabled in 'malloc'. While this
229 cache can be disabled on a per-application basis using tunables
230 (set glibc.malloc.tcache_count to zero), this option can be used to
231 remove it from the build completely.
232
233 '--build=BUILD-SYSTEM'
234 '--host=HOST-SYSTEM'
235 These options are for cross-compiling. If you specify both options
236 and BUILD-SYSTEM is different from HOST-SYSTEM, 'configure' will
237 prepare to cross-compile the GNU C Library from BUILD-SYSTEM to be
238 used on HOST-SYSTEM. You'll probably need the '--with-headers'
239 option too, and you may have to override CONFIGURE's selection of
240 the compiler and/or binutils.
241
242 If you only specify '--host', 'configure' will prepare for a native
243 compile but use what you specify instead of guessing what your
244 system is. This is most useful to change the CPU submodel. For
245 example, if 'configure' guesses your machine as 'i686-pc-linux-gnu'
246 but you want to compile a library for 586es, give
247 '--host=i586-pc-linux-gnu' or just '--host=i586-linux' and add the
248 appropriate compiler flags ('-mcpu=i586' will do the trick) to
249 'CC'.
250
251 If you specify just '--build', 'configure' will get confused.
252
253 '--with-pkgversion=VERSION'
254 Specify a description, possibly including a build number or build
255 date, of the binaries being built, to be included in '--version'
256 output from programs installed with the GNU C Library. For
257 example, '--with-pkgversion='FooBar GNU/Linux glibc build 123''.
258 The default value is 'GNU libc'.
259
260 '--with-bugurl=URL'
261 Specify the URL that users should visit if they wish to report a
262 bug, to be included in '--help' output from programs installed with
263 the GNU C Library. The default value refers to the main
264 bug-reporting information for the GNU C Library.
265
266 To build the library and related programs, type 'make'. This will
267 produce a lot of output, some of which may look like errors from 'make'
268 but aren't. Look for error messages from 'make' containing '***'.
269 Those indicate that something is seriously wrong.
270
271 The compilation process can take a long time, depending on the
272 configuration and the speed of your machine. Some complex modules may
273 take a very long time to compile, as much as several minutes on slower
274 machines. Do not panic if the compiler appears to hang.
275
276 If you want to run a parallel make, simply pass the '-j' option with
277 an appropriate numeric parameter to 'make'. You need a recent GNU
278 'make' version, though.
279
280 To build and run test programs which exercise some of the library
281 facilities, type 'make check'. If it does not complete successfully, do
282 not use the built library, and report a bug after verifying that the
283 problem is not already known. *Note Reporting Bugs::, for instructions
284 on reporting bugs. Note that some of the tests assume they are not
285 being run by 'root'. We recommend you compile and test the GNU C
286 Library as an unprivileged user.
287
288 Before reporting bugs make sure there is no problem with your system.
289 The tests (and later installation) use some pre-existing files of the
290 system such as '/etc/passwd', '/etc/nsswitch.conf' and others. These
291 files must all contain correct and sensible content.
292
293 Normally, 'make check' will run all the tests before reporting all
294 problems found and exiting with error status if any problems occurred.
295 You can specify 'stop-on-test-failure=y' when running 'make check' to
296 make the test run stop and exit with an error status immediately when a
297 failure occurs.
298
299 To format the 'GNU C Library Reference Manual' for printing, type
300 'make dvi'. You need a working TeX installation to do this. The
301 distribution builds the on-line formatted version of the manual, as Info
302 files, as part of the build process. You can build them manually with
303 'make info'.
304
305 The library has a number of special-purpose configuration parameters
306 which you can find in 'Makeconfig'. These can be overwritten with the
307 file 'configparms'. To change them, create a 'configparms' in your
308 build directory and add values as appropriate for your system. The file
309 is included and parsed by 'make' and has to follow the conventions for
310 makefiles.
311
312 It is easy to configure the GNU C Library for cross-compilation by
313 setting a few variables in 'configparms'. Set 'CC' to the
314 cross-compiler for the target you configured the library for; it is
315 important to use this same 'CC' value when running 'configure', like
316 this: 'configure TARGET CC=TARGET-gcc'. Set 'BUILD_CC' to the compiler
317 to use for programs run on the build system as part of compiling the
318 library. You may need to set 'AR' to cross-compiling versions of 'ar'
319 if the native tools are not configured to work with object files for the
320 target you configured for. When cross-compiling the GNU C Library, it
321 may be tested using 'make check
322 test-wrapper="SRCDIR/scripts/cross-test-ssh.sh HOSTNAME"', where SRCDIR
323 is the absolute directory name for the main source directory and
324 HOSTNAME is the host name of a system that can run the newly built
325 binaries of the GNU C Library. The source and build directories must be
326 visible at the same locations on both the build system and HOSTNAME.
327
328 In general, when testing the GNU C Library, 'test-wrapper' may be set
329 to the name and arguments of any program to run newly built binaries.
330 This program must preserve the arguments to the binary being run, its
331 working directory and the standard input, output and error file
332 descriptors. If 'TEST-WRAPPER env' will not work to run a program with
333 environment variables set, then 'test-wrapper-env' must be set to a
334 program that runs a newly built program with environment variable
335 assignments in effect, those assignments being specified as 'VAR=VALUE'
336 before the name of the program to be run. If multiple assignments to
337 the same variable are specified, the last assignment specified must take
338 precedence. Similarly, if 'TEST-WRAPPER env -i' will not work to run a
339 program with an environment completely empty of variables except those
340 directly assigned, then 'test-wrapper-env-only' must be set; its use has
341 the same syntax as 'test-wrapper-env', the only difference in its
342 semantics being starting with an empty set of environment variables
343 rather than the ambient set.
344
345 Installing the C Library
346 ========================
347
348 To install the library and its header files, and the Info files of the
349 manual, type 'make install'. This will build things, if necessary,
350 before installing them; however, you should still compile everything
351 first. If you are installing the GNU C Library as your primary C
352 library, we recommend that you shut the system down to single-user mode
353 first, and reboot afterward. This minimizes the risk of breaking things
354 when the library changes out from underneath.
355
356 'make install' will do the entire job of upgrading from a previous
357 installation of the GNU C Library version 2.x. There may sometimes be
358 headers left behind from the previous installation, but those are
359 generally harmless. If you want to avoid leaving headers behind you can
360 do things in the following order.
361
362 You must first build the library ('make'), optionally check it ('make
363 check'), switch the include directories and then install ('make
364 install'). The steps must be done in this order. Not moving the
365 directory before install will result in an unusable mixture of header
366 files from both libraries, but configuring, building, and checking the
367 library requires the ability to compile and run programs against the old
368 library. The new '/usr/include', after switching the include
369 directories and before installing the library should contain the Linux
370 headers, but nothing else. If you do this, you will need to restore any
371 headers from libraries other than the GNU C Library yourself after
372 installing the library.
373
374 You can install the GNU C Library somewhere other than where you
375 configured it to go by setting the 'DESTDIR' GNU standard make variable
376 on the command line for 'make install'. The value of this variable is
377 prepended to all the paths for installation. This is useful when
378 setting up a chroot environment or preparing a binary distribution. The
379 directory should be specified with an absolute file name. Installing
380 with the 'prefix' and 'exec_prefix' GNU standard make variables set is
381 not supported.
382
383 The GNU C Library includes a daemon called 'nscd', which you may or
384 may not want to run. 'nscd' caches name service lookups; it can
385 dramatically improve performance with NIS+, and may help with DNS as
386 well.
387
388 One auxiliary program, '/usr/libexec/pt_chown', is installed setuid
389 'root' if the '--enable-pt_chown' configuration option is used. This
390 program is invoked by the 'grantpt' function; it sets the permissions on
391 a pseudoterminal so it can be used by the calling process. If you are
392 using a Linux kernel with the 'devpts' filesystem enabled and mounted at
393 '/dev/pts', you don't need this program.
394
395 After installation you should configure the timezone and install
396 locales for your system. The time zone configuration ensures that your
397 system time matches the time for your current timezone. The locales
398 ensure that the display of information on your system matches the
399 expectations of your language and geographic region.
400
401 The GNU C Library is able to use two kinds of localization
402 information sources, the first is a locale database named
403 'locale-archive' which is generally installed as
404 '/usr/lib/locale/locale-archive'. The locale archive has the benefit of
405 taking up less space and being very fast to load, but only if you plan
406 to install sixty or more locales. If you plan to install one or two
407 locales you can instead install individual locales into their self-named
408 directories e.g. '/usr/lib/locale/en_US.utf8'. For example to install
409 the German locale using the character set for UTF-8 with name 'de_DE'
410 into the locale archive issue the command 'localedef -i de_DE -f UTF-8
411 de_DE', and to install just the one locale issue the command 'localedef
412 --no-archive -i de_DE -f UTF-8 de_DE'. To configure all locales that
413 are supported by the GNU C Library, you can issue from your build
414 directory the command 'make localedata/install-locales' to install all
415 locales into the locale archive or 'make
416 localedata/install-locale-files' to install all locales as files in the
417 default configured locale installation directory (derived from
418 '--prefix' or '--localedir'). To install into an alternative system
419 root use 'DESTDIR' e.g. 'make localedata/install-locale-files
420 DESTDIR=/opt/glibc', but note that this does not change the configured
421 prefix.
422
423 To configure the locally used timezone, set the 'TZ' environment
424 variable. The script 'tzselect' helps you to select the right value.
425 As an example, for Germany, 'tzselect' would tell you to use
426 'TZ='Europe/Berlin''. For a system wide installation (the given paths
427 are for an installation with '--prefix=/usr'), link the timezone file
428 which is in '/usr/share/zoneinfo' to the file '/etc/localtime'. For
429 Germany, you might execute 'ln -s /usr/share/zoneinfo/Europe/Berlin
430 /etc/localtime'.
431
432 Recommended Tools for Compilation
433 =================================
434
435 We recommend installing the following GNU tools before attempting to
436 build the GNU C Library:
437
438 * GNU 'make' 4.0 or newer
439
440 As of relase time, GNU 'make' 4.2.1 is the newest verified to work
441 to build the GNU C Library.
442
443 * GCC 4.9 or newer
444
445 GCC 4.9 or higher is required. In general it is recommended to use
446 the newest version of the compiler that is known to work for
447 building the GNU C Library, as newer compilers usually produce
448 better code. As of release time, GCC 8.1.1 is the newest compiler
449 verified to work to build the GNU C Library.
450
451 For PowerPC 64-bits little-endian (powerpc64le), GCC 6.2 or higher
452 is required. This compiler version is the first to provide the
453 features required for building the GNU C Library with support for
454 '_Float128'.
455
456 For multi-arch support it is recommended to use a GCC which has
457 been built with support for GNU indirect functions. This ensures
458 that correct debugging information is generated for functions
459 selected by IFUNC resolvers. This support can either be enabled by
460 configuring GCC with '--enable-gnu-indirect-function', or by
461 enabling it by default by setting 'default_gnu_indirect_function'
462 variable for a particular architecture in the GCC source file
463 'gcc/config.gcc'.
464
465 You can use whatever compiler you like to compile programs that use
466 the GNU C Library.
467
468 Check the FAQ for any special compiler issues on particular
469 platforms.
470
471 * GNU 'binutils' 2.25 or later
472
473 You must use GNU 'binutils' (as and ld) to build the GNU C Library.
474 No other assembler or linker has the necessary functionality at the
475 moment. As of release time, GNU 'binutils' 2.31.1 is the newest
476 verified to work to build the GNU C Library.
477
478 * GNU 'texinfo' 4.7 or later
479
480 To correctly translate and install the Texinfo documentation you
481 need this version of the 'texinfo' package. Earlier versions do
482 not understand all the tags used in the document, and the
483 installation mechanism for the info files is not present or works
484 differently. As of release time, 'texinfo' 6.5 is the newest
485 verified to work to build the GNU C Library.
486
487 * GNU 'awk' 3.1.2, or higher
488
489 'awk' is used in several places to generate files. Some 'gawk'
490 extensions are used, including the 'asorti' function, which was
491 introduced in version 3.1.2 of 'gawk'. As of release time, 'gawk'
492 version 4.2.1 is the newest verified to work to build the GNU C
493 Library.
494
495 * GNU 'bison' 2.7 or later
496
497 'bison' is used to generate the 'yacc' parser code in the 'intl'
498 subdirectory. As of release time, 'bison' version 3.0.4 is the
499 newest verified to work to build the GNU C Library.
500
501 * Perl 5
502
503 Perl is not required, but if present it is used in some tests and
504 the 'mtrace' program, to build the GNU C Library manual, as well as
505 to regenerate 'locale/C-translit.h' if its source files are
506 modified. As of release time 'perl' version 5.28.0 is the newest
507 verified to work to build the GNU C Library.
508
509 * GNU 'sed' 3.02 or newer
510
511 'Sed' is used in several places to generate files. Most scripts
512 work with any version of 'sed'. As of release time, 'sed' version
513 4.5 is the newest verified to work to build the GNU C Library.
514
515 * Python 2.7/3.4 or later
516
517 Python is required to run some tests. As of release time, Python
518 3.6 is the newest verified to work for testing the GNU C Library.
519
520 * PExpect 4.0
521
522 The pretty printer tests drive GDB through test programs and
523 compare its output to the printers'. PExpect is used to capture
524 the output of GDB, and should be compatible with the Python version
525 in your system. As of release time PExpect 4.3 is the newest
526 verified to work to test the pretty printers.
527
528 * GDB 7.8 or later with support for Python 2.7/3.4 or later
529
530 GDB itself needs to be configured with Python support in order to
531 use the pretty printers. Notice that your system having Python
532 available doesn't imply that GDB supports it, nor that your
533 system's Python and GDB's have the same version. As of release
534 time GNU 'debugger' 8.0.1 is the newest verified to work to test
535 the pretty printers.
536
537 Unless Python, PExpect and GDB with Python support are present, the
538 printer tests will report themselves as 'UNSUPPORTED'. Notice that
539 some of the printer tests require the GNU C Library to be compiled
540 with debugging symbols.
541
542 If you change any of the 'configure.ac' files you will also need
543
544 * GNU 'autoconf' 2.69 (exactly)
545
546 and if you change any of the message translation files you will need
547
548 * GNU 'gettext' 0.10.36 or later
549
550 As of release time, GNU 'gettext' version 0.19.8.1 is the newest
551 version verified to work to build the GNU C Library.
552
553 You may also need these packages if you upgrade your source tree using
554 patches, although we try to avoid this.
555
556 Specific advice for GNU/Linux systems
557 =====================================
558
559 If you are installing the GNU C Library on GNU/Linux systems, you need
560 to have the header files from a 3.2 or newer kernel around for
561 reference. (For the ia64 architecture, you need version 3.2.18 or newer
562 because this is the first version with support for the 'accept4' system
563 call.) These headers must be installed using 'make headers_install';
564 the headers present in the kernel source directory are not suitable for
565 direct use by the GNU C Library. You do not need to use that kernel,
566 just have its headers installed where the GNU C Library can access them,
567 referred to here as INSTALL-DIRECTORY. The easiest way to do this is to
568 unpack it in a directory such as '/usr/src/linux-VERSION'. In that
569 directory, run 'make headers_install
570 INSTALL_HDR_PATH=INSTALL-DIRECTORY'. Finally, configure the GNU C
571 Library with the option '--with-headers=INSTALL-DIRECTORY/include'. Use
572 the most recent kernel you can get your hands on. (If you are
573 cross-compiling the GNU C Library, you need to specify
574 'ARCH=ARCHITECTURE' in the 'make headers_install' command, where
575 ARCHITECTURE is the architecture name used by the Linux kernel, such as
576 'x86' or 'powerpc'.)
577
578 After installing the GNU C Library, you may need to remove or rename
579 directories such as '/usr/include/linux' and '/usr/include/asm', and
580 replace them with copies of directories such as 'linux' and 'asm' from
581 'INSTALL-DIRECTORY/include'. All directories present in
582 'INSTALL-DIRECTORY/include' should be copied, except that the GNU C
583 Library provides its own version of '/usr/include/scsi'; the files
584 provided by the kernel should be copied without replacing those provided
585 by the GNU C Library. The 'linux', 'asm' and 'asm-generic' directories
586 are required to compile programs using the GNU C Library; the other
587 directories describe interfaces to the kernel but are not required if
588 not compiling programs using those interfaces. You do not need to copy
589 kernel headers if you did not specify an alternate kernel header source
590 using '--with-headers'.
591
592 The Filesystem Hierarchy Standard for GNU/Linux systems expects some
593 components of the GNU C Library installation to be in '/lib' and some in
594 '/usr/lib'. This is handled automatically if you configure the GNU C
595 Library with '--prefix=/usr'. If you set some other prefix or allow it
596 to default to '/usr/local', then all the components are installed there.
597
598 Reporting Bugs
599 ==============
600
601 There are probably bugs in the GNU C Library. There are certainly
602 errors and omissions in this manual. If you report them, they will get
603 fixed. If you don't, no one will ever know about them and they will
604 remain unfixed for all eternity, if not longer.
605
606 It is a good idea to verify that the problem has not already been
607 reported. Bugs are documented in two places: The file 'BUGS' describes
608 a number of well known bugs and the central GNU C Library bug tracking
609 system has a WWW interface at <https://sourceware.org/bugzilla/>. The
610 WWW interface gives you access to open and closed reports. A closed
611 report normally includes a patch or a hint on solving the problem.
612
613 To report a bug, first you must find it. With any luck, this will be
614 the hard part. Once you've found a bug, make sure it's really a bug. A
615 good way to do this is to see if the GNU C Library behaves the same way
616 some other C library does. If so, probably you are wrong and the
617 libraries are right (but not necessarily). If not, one of the libraries
618 is probably wrong. It might not be the GNU C Library. Many historical
619 Unix C libraries permit things that we don't, such as closing a file
620 twice.
621
622 If you think you have found some way in which the GNU C Library does
623 not conform to the ISO and POSIX standards (*note Standards and
624 Portability::), that is definitely a bug. Report it!
625
626 Once you're sure you've found a bug, try to narrow it down to the
627 smallest test case that reproduces the problem. In the case of a C
628 library, you really only need to narrow it down to one library function
629 call, if possible. This should not be too difficult.
630
631 The final step when you have a simple test case is to report the bug.
632 Do this at <http://www.gnu.org/software/libc/bugs.html>.
633
634 If you are not sure how a function should behave, and this manual
635 doesn't tell you, that's a bug in the manual. Report that too! If the
636 function's behavior disagrees with the manual, then either the library
637 or the manual has a bug, so report the disagreement. If you find any
638 errors or omissions in this manual, please report them to the bug
639 database. If you refer to specific sections of the manual, please
640 include the section names for easier identification.