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1Installing the GNU C Library
2****************************
41aa20c2 3
6a3951a0 4Before you do anything else, you should read the FAQ at
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5<https://sourceware.org/glibc/wiki/FAQ>. It answers common questions
6and describes problems you may experience with compilation and
7installation.
41aa20c2 8
00c1176b 9 You will need recent versions of several GNU tools: definitely GCC
fe959e1e 10and GNU Make, and possibly others. *Note Tools for Compilation::,
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11below.
12
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13Configuring and compiling the GNU C Library
14===========================================
00c1176b 15
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16The GNU C Library cannot be compiled in the source directory. You must
17build it in a separate build directory. For example, if you have
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18unpacked the GNU C Library sources in '/src/gnu/glibc-VERSION', create a
19directory '/src/gnu/glibc-build' to put the object files in. This
20allows removing the whole build directory in case an error occurs, which
21is the safest way to get a fresh start and should always be done.
00c1176b 22
a8db092e 23 From your object directory, run the shell script 'configure' located
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24at the top level of the source tree. In the scenario above, you'd type
25
f1e86fca 26 $ ../glibc-VERSION/configure ARGS...
00c1176b 27
3858bf28 28 Please note that even though you're building in a separate build
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29directory, the compilation may need to create or modify files and
30directories in the source directory.
f05f5ca3 31
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32'configure' takes many options, but the only one that is usually
33mandatory is '--prefix'. This option tells 'configure' where you want
34the GNU C Library installed. This defaults to '/usr/local', but the
1f77f049 35normal setting to install as the standard system library is
a8db092e 36'--prefix=/usr' for GNU/Linux systems and '--prefix=' (an empty prefix)
1f77f049 37for GNU/Hurd systems.
00c1176b 38
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39 It may also be useful to pass 'CC=COMPILER' and 'CFLAGS=FLAGS'
40arguments to 'configure'. 'CC' selects the C compiler that will be
41used, and 'CFLAGS' sets optimization options for the compiler. Any
42compiler options required for all compilations, such as options
43selecting an ABI or a processor for which to generate code, should be
44included in 'CC'. Options that may be overridden by the GNU C Library
45build system for particular files, such as for optimization and
46debugging, should go in 'CFLAGS'. The default value of 'CFLAGS' is '-g
47-O2', and the GNU C Library cannot be compiled without optimization, so
48if 'CFLAGS' is specified it must enable optimization. For example:
49
50 $ ../glibc-VERSION/configure CC="gcc -m32" CFLAGS="-O3"
00c1176b 51
bd952512 52 The following list describes all of the available options for
a8db092e 53'configure':
00c1176b 54
a8db092e 55'--prefix=DIRECTORY'
00c1176b 56 Install machine-independent data files in subdirectories of
a8db092e 57 'DIRECTORY'. The default is to install in '/usr/local'.
00c1176b 58
a8db092e 59'--exec-prefix=DIRECTORY'
00c1176b 60 Install the library and other machine-dependent files in
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61 subdirectories of 'DIRECTORY'. The default is to the '--prefix'
62 directory if that option is specified, or '/usr/local' otherwise.
00c1176b 63
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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
1f77f049 67 describing the interface to the kernel. The GNU C Library will
a8db092e 68 normally look in '/usr/include' for them, but if you specify this
1f77f049 69 option, it will look in DIRECTORY instead.
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70
71 This option is primarily of use on a system where the headers in
a8db092e 72 '/usr/include' come from an older version of the GNU C Library.
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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
a8db092e 75 set of kernel headers than the ones found in '/usr/include'.
41aa20c2 76
a8db092e 77'--enable-kernel=VERSION'
90d1d40b 78 This option is currently only useful on GNU/Linux systems. The
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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
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84'--with-binutils=DIRECTORY'
85 Use the binutils (assembler and linker) in 'DIRECTORY', not the
6736e93b 86 ones the C compiler would default to. You can use this option if
41aa20c2 87 the default binutils on your system cannot deal with all the
a8db092e 88 constructs in the GNU C Library. In that case, 'configure' will
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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.
41aa20c2 92
a8db092e 93'--disable-shared'
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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.
41aa20c2 97
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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
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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.
9d7a3741 108
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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
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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
a8db092e 125'--disable-profile'
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126 Don't build libraries with profiling information. You may want to
127 use this option if you don't plan to do profiling.
41aa20c2 128
a8db092e 129'--enable-static-nss'
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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
a8db092e 135'--enable-hardcoded-path-in-tests'
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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
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140'--disable-timezone-tools'
141 By default, timezone related utilities ('zic', 'zdump', and
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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.
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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
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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
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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
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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
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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
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184 with, so new warnings cause the build with '-Werror' to fail), you
185 can configure with '--disable-werror'.
186
21933112 187'--disable-mathvec'
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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.
21933112 190
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191'--enable-tunables'
192 Tunables support allows additional library parameters to be
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193 customized at runtime. This feature is enabled by default. This
194 option can take the following values:
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195
196 'yes'
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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.
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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'.
67e58f39 209
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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
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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
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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
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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
db9881ec 249 'CC'.
1792d4db 250
a8db092e 251 If you specify just '--build', 'configure' will get confused.
41aa20c2 252
a8db092e 253'--with-pkgversion=VERSION'
8b748aed 254 Specify a description, possibly including a build number or build
a8db092e 255 date, of the binaries being built, to be included in '--version'
8b748aed 256 output from programs installed with the GNU C Library. For
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257 example, '--with-pkgversion='FooBar GNU/Linux glibc build 123''.
258 The default value is 'GNU libc'.
8b748aed 259
a8db092e 260'--with-bugurl=URL'
8b748aed 261 Specify the URL that users should visit if they wish to report a
a8db092e 262 bug, to be included in '--help' output from programs installed with
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263 the GNU C Library. The default value refers to the main
264 bug-reporting information for the GNU C Library.
265
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266 To build the library and related programs, type 'make'. This will
267produce a lot of output, some of which may look like errors from 'make'
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268but aren't. Look for error messages from 'make' containing '***'.
269Those indicate that something is seriously wrong.
41aa20c2 270
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271 The compilation process can take a long time, depending on the
272configuration and the speed of your machine. Some complex modules may
273take a very long time to compile, as much as several minutes on slower
274machines. Do not panic if the compiler appears to hang.
00c1176b 275
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276 If you want to run a parallel make, simply pass the '-j' option with
277an appropriate numeric parameter to 'make'. You need a recent GNU
278'make' version, though.
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279
280 To build and run test programs which exercise some of the library
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281facilities, type 'make check'. If it does not complete successfully, do
282not use the built library, and report a bug after verifying that the
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283problem is not already known. *Note Reporting Bugs::, for instructions
284on reporting bugs. Note that some of the tests assume they are not
a8db092e 285being run by 'root'. We recommend you compile and test the GNU C
1f77f049 286Library as an unprivileged user.
41aa20c2 287
8d4b5a8a 288 Before reporting bugs make sure there is no problem with your system.
6736e93b 289The tests (and later installation) use some pre-existing files of the
a8db092e 290system such as '/etc/passwd', '/etc/nsswitch.conf' and others. These
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291files must all contain correct and sensible content.
292
a8db092e 293 Normally, 'make check' will run all the tests before reporting all
d6fe5e58 294problems found and exiting with error status if any problems occurred.
a8db092e 295You can specify 'stop-on-test-failure=y' when running 'make check' to
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296make the test run stop and exit with an error status immediately when a
297failure occurs.
298
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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
301distribution builds the on-line formatted version of the manual, as Info
302files, as part of the build process. You can build them manually with
303'make info'.
1792d4db 304
c0389ee4 305 The library has a number of special-purpose configuration parameters
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306which you can find in 'Makeconfig'. These can be overwritten with the
307file 'configparms'. To change them, create a 'configparms' in your
308build directory and add values as appropriate for your system. The file
309is included and parsed by 'make' and has to follow the conventions for
310makefiles.
c0389ee4 311
1f77f049 312 It is easy to configure the GNU C Library for cross-compilation by
a8db092e 313setting a few variables in 'configparms'. Set 'CC' to the
c0389ee4 314cross-compiler for the target you configured the library for; it is
a8db092e 315important to use this same 'CC' value when running 'configure', like
db9881ec 316this: 'configure TARGET CC=TARGET-gcc'. Set 'BUILD_CC' to the compiler
6736e93b 317to use for programs run on the build system as part of compiling the
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318library. You may need to set 'AR' to cross-compiling versions of 'ar'
319if the native tools are not configured to work with object files for the
320target you configured for. When cross-compiling the GNU C Library, it
321may be tested using 'make check
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322test-wrapper="SRCDIR/scripts/cross-test-ssh.sh HOSTNAME"', where SRCDIR
323is the absolute directory name for the main source directory and
324HOSTNAME is the host name of a system that can run the newly built
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325binaries of the GNU C Library. The source and build directories must be
326visible at the same locations on both the build system and HOSTNAME.
c0389ee4 327
a8db092e 328 In general, when testing the GNU C Library, 'test-wrapper' may be set
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329to the name and arguments of any program to run newly built binaries.
330This program must preserve the arguments to the binary being run, its
8540f6d2 331working directory and the standard input, output and error file
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332descriptors. If 'TEST-WRAPPER env' will not work to run a program with
333environment variables set, then 'test-wrapper-env' must be set to a
8540f6d2 334program that runs a newly built program with environment variable
a8db092e 335assignments in effect, those assignments being specified as 'VAR=VALUE'
8540f6d2 336before the name of the program to be run. If multiple assignments to
a8db092e 337the same variable are specified, the last assignment specified must take
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338precedence. Similarly, if 'TEST-WRAPPER env -i' will not work to run a
339program with an environment completely empty of variables except those
340directly assigned, then 'test-wrapper-env-only' must be set; its use has
341the same syntax as 'test-wrapper-env', the only difference in its
342semantics being starting with an empty set of environment variables
343rather than the ambient set.
0eb69512 344
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345Installing the C Library
346========================
41aa20c2 347
80ed68b7 348To install the library and its header files, and the Info files of the
a8db092e 349manual, type 'make install'. This will build things, if necessary,
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350before installing them; however, you should still compile everything
351first. If you are installing the GNU C Library as your primary C
352library, we recommend that you shut the system down to single-user mode
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353first, and reboot afterward. This minimizes the risk of breaking things
354when the library changes out from underneath.
1792d4db 355
a8db092e 356 'make install' will do the entire job of upgrading from a previous
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357installation of the GNU C Library version 2.x. There may sometimes be
358headers left behind from the previous installation, but those are
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359generally harmless. If you want to avoid leaving headers behind you can
360do things in the following order.
c0389ee4 361
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362 You must first build the library ('make'), optionally check it ('make
363check'), switch the include directories and then install ('make
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364install'). The steps must be done in this order. Not moving the
365directory before install will result in an unusable mixture of header
366files from both libraries, but configuring, building, and checking the
367library requires the ability to compile and run programs against the old
a8db092e 368library. The new '/usr/include', after switching the include
02c4bbad 369directories and before installing the library should contain the Linux
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370headers, but nothing else. If you do this, you will need to restore any
371headers from libraries other than the GNU C Library yourself after
1f77f049 372installing the library.
c0389ee4 373
1f77f049 374 You can install the GNU C Library somewhere other than where you
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375configured it to go by setting the 'DESTDIR' GNU standard make variable
376on the command line for 'make install'. The value of this variable is
1f77f049 377prepended to all the paths for installation. This is useful when
a8db092e 378setting up a chroot environment or preparing a binary distribution. The
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379directory should be specified with an absolute file name. Installing
380with the 'prefix' and 'exec_prefix' GNU standard make variables set is
381not supported.
1792d4db 382
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383 The GNU C Library includes a daemon called 'nscd', which you may or
384may not want to run. 'nscd' caches name service lookups; it can
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385dramatically improve performance with NIS+, and may help with DNS as
386well.
1792d4db 387
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388 One auxiliary program, '/usr/libexec/pt_chown', is installed setuid
389'root' if the '--enable-pt_chown' configuration option is used. This
390program is invoked by the 'grantpt' function; it sets the permissions on
391a pseudoterminal so it can be used by the calling process. If you are
392using a Linux kernel with the 'devpts' filesystem enabled and mounted at
393'/dev/pts', you don't need this program.
41aa20c2 394
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395 After installation you should configure the timezone and install
396locales for your system. The time zone configuration ensures that your
397system time matches the time for your current timezone. The locales
398ensure that the display of information on your system matches the
399expectations of your language and geographic region.
400
401 The GNU C Library is able to use two kinds of localization
402information 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
405taking up less space and being very fast to load, but only if you plan
406to install sixty or more locales. If you plan to install one or two
407locales you can instead install individual locales into their self-named
408directories e.g. '/usr/lib/locale/en_US.utf8'. For example to install
409the German locale using the character set for UTF-8 with name 'de_DE'
410into the locale archive issue the command 'localedef -i de_DE -f UTF-8
411de_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
a8db092e 413are supported by the GNU C Library, you can issue from your build
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414directory the command 'make localedata/install-locales' to install all
415locales into the locale archive or 'make
416localedata/install-locale-files' to install all locales as files in the
417default configured locale installation directory (derived from
418'--prefix' or '--localedir'). To install into an alternative system
419root use 'DESTDIR' e.g. 'make localedata/install-locale-files
420DESTDIR=/opt/glibc', but note that this does not change the configured
421prefix.
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422
423 To configure the locally used timezone, set the 'TZ' environment
424variable. The script 'tzselect' helps you to select the right value.
425As an example, for Germany, 'tzselect' would tell you to use
426'TZ='Europe/Berlin''. For a system wide installation (the given paths
427are for an installation with '--prefix=/usr'), link the timezone file
428which is in '/usr/share/zoneinfo' to the file '/etc/localtime'. For
429Germany, you might execute 'ln -s /usr/share/zoneinfo/Europe/Berlin
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430/etc/localtime'.
431
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432Recommended Tools for Compilation
433=================================
41aa20c2 434
80ed68b7 435We recommend installing the following GNU tools before attempting to
1f77f049 436build the GNU C Library:
41aa20c2 437
f2873d2d 438 * GNU 'make' 4.0 or newer
41aa20c2 439
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440 As of relase time, GNU 'make' 4.2.1 is the newest verified to work
441 to build the GNU C Library.
442
4add8674 443 * GCC 4.9 or newer
0e7727f7 444
4add8674 445 GCC 4.9 or higher is required. In general it is recommended to use
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446 the newest version of the compiler that is known to work for
447 building the GNU C Library, as newer compilers usually produce
f650932b 448 better code. As of release time, GCC 8.1.1 is the newest compiler
4863355a 449 verified to work to build the GNU C Library.
91ea72b7 450
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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
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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
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465 You can use whatever compiler you like to compile programs that use
466 the GNU C Library.
41aa20c2 467
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468 Check the FAQ for any special compiler issues on particular
469 platforms.
5713a71e 470
073e8fa7 471 * GNU 'binutils' 2.25 or later
41aa20c2 472
a8db092e 473 You must use GNU 'binutils' (as and ld) to build the GNU C Library.
7a49a7d5 474 No other assembler or linker has the necessary functionality at the
f650932b 475 moment. As of release time, GNU 'binutils' 2.31.1 is the newest
04cb913d 476 verified to work to build the GNU C Library.
41aa20c2 477
a8db092e 478 * GNU 'texinfo' 4.7 or later
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479
480 To correctly translate and install the Texinfo documentation you
a8db092e 481 need this version of the 'texinfo' package. Earlier versions do
41aa20c2 482 not understand all the tags used in the document, and the
1792d4db 483 installation mechanism for the info files is not present or works
93493119 484 differently. As of release time, 'texinfo' 6.5 is the newest
04cb913d 485 verified to work to build the GNU C Library.
41aa20c2 486
a8db092e 487 * GNU 'awk' 3.1.2, or higher
00c1176b 488
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489 'awk' is used in several places to generate files. Some 'gawk'
490 extensions are used, including the 'asorti' function, which was
2c8f75f7 491 introduced in version 3.1.2 of 'gawk'. As of release time, 'gawk'
f650932b 492 version 4.2.1 is the newest verified to work to build the GNU C
2c8f75f7 493 Library.
41aa20c2 494
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495 * GNU 'bison' 2.7 or later
496
497 'bison' is used to generate the 'yacc' parser code in the 'intl'
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498 subdirectory. As of release time, 'bison' version 3.0.4 is the
499 newest verified to work to build the GNU C Library.
1faaf703 500
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501 * Perl 5
502
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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.
41aa20c2 508
a8db092e 509 * GNU 'sed' 3.02 or newer
c0389ee4 510
a8db092e 511 'Sed' is used in several places to generate files. Most scripts
2c8f75f7 512 work with any version of 'sed'. As of release time, 'sed' version
f650932b 513 4.5 is the newest verified to work to build the GNU C Library.
c0389ee4 514
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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
a8db092e 542If you change any of the 'configure.ac' files you will also need
0cc70fcf 543
a8db092e 544 * GNU 'autoconf' 2.69 (exactly)
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545
546and if you change any of the message translation files you will need
547
a8db092e 548 * GNU 'gettext' 0.10.36 or later
41aa20c2 549
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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
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553You may also need these packages if you upgrade your source tree using
554patches, although we try to avoid this.
555
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556Specific advice for GNU/Linux systems
557=====================================
80ed68b7 558
a7a93d50 559If you are installing the GNU C Library on GNU/Linux systems, you need
5b4ecd3f 560to have the header files from a 3.2 or newer kernel around for
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561reference. (For the ia64 architecture, you need version 3.2.18 or newer
562because this is the first version with support for the 'accept4' system
563call.) These headers must be installed using 'make headers_install';
564the headers present in the kernel source directory are not suitable for
565direct use by the GNU C Library. You do not need to use that kernel,
566just have its headers installed where the GNU C Library can access them,
567referred to here as INSTALL-DIRECTORY. The easiest way to do this is to
568unpack it in a directory such as '/usr/src/linux-VERSION'. In that
569directory, run 'make headers_install
1f77f049 570INSTALL_HDR_PATH=INSTALL-DIRECTORY'. Finally, configure the GNU C
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571Library with the option '--with-headers=INSTALL-DIRECTORY/include'. Use
572the most recent kernel you can get your hands on. (If you are
1f77f049 573cross-compiling the GNU C Library, you need to specify
a8db092e 574'ARCH=ARCHITECTURE' in the 'make headers_install' command, where
1f77f049 575ARCHITECTURE is the architecture name used by the Linux kernel, such as
a8db092e 576'x86' or 'powerpc'.)
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577
578 After installing the GNU C Library, you may need to remove or rename
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579directories such as '/usr/include/linux' and '/usr/include/asm', and
580replace 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
583Library provides its own version of '/usr/include/scsi'; the files
584provided by the kernel should be copied without replacing those provided
585by the GNU C Library. The 'linux', 'asm' and 'asm-generic' directories
586are required to compile programs using the GNU C Library; the other
587directories describe interfaces to the kernel but are not required if
588not compiling programs using those interfaces. You do not need to copy
589kernel headers if you did not specify an alternate kernel header source
590using '--with-headers'.
1f77f049 591
a7a93d50 592 The Filesystem Hierarchy Standard for GNU/Linux systems expects some
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593components 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
595Library with '--prefix=/usr'. If you set some other prefix or allow it
596to default to '/usr/local', then all the components are installed there.
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598Reporting Bugs
599==============
41aa20c2 600
1f77f049 601There are probably bugs in the GNU C Library. There are certainly
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602errors and omissions in this manual. If you report them, they will get
603fixed. If you don't, no one will ever know about them and they will
604remain unfixed for all eternity, if not longer.
605
bd952512 606 It is a good idea to verify that the problem has not already been
a8db092e 607reported. Bugs are documented in two places: The file 'BUGS' describes
8b748aed 608a number of well known bugs and the central GNU C Library bug tracking
a306c790 609system has a WWW interface at <https://sourceware.org/bugzilla/>. The
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610WWW interface gives you access to open and closed reports. A closed
611report normally includes a patch or a hint on solving the problem.
6736e93b 612
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613 To report a bug, first you must find it. With any luck, this will be
614the hard part. Once you've found a bug, make sure it's really a bug. A
615good way to do this is to see if the GNU C Library behaves the same way
616some other C library does. If so, probably you are wrong and the
617libraries are right (but not necessarily). If not, one of the libraries
618is probably wrong. It might not be the GNU C Library. Many historical
619Unix C libraries permit things that we don't, such as closing a file
620twice.
1792d4db 621
1f77f049 622 If you think you have found some way in which the GNU C Library does
1792d4db 623not conform to the ISO and POSIX standards (*note Standards and
c0389ee4 624Portability::), that is definitely a bug. Report it!
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625
626 Once you're sure you've found a bug, try to narrow it down to the
627smallest test case that reproduces the problem. In the case of a C
628library, you really only need to narrow it down to one library function
629call, 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.
a8db092e 632Do this at <http://www.gnu.org/software/libc/bugs.html>.
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633
634 If you are not sure how a function should behave, and this manual
635doesn't tell you, that's a bug in the manual. Report that too! If the
636function's behavior disagrees with the manual, then either the library
637or the manual has a bug, so report the disagreement. If you find any
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638errors or omissions in this manual, please report them to the bug
639database. If you refer to specific sections of the manual, please
640include the section names for easier identification.
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