INSTALL

   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 ‘--with-rtld-early-cflags=CFLAGS’
 110      Use additional compiler flags CFLAGS to build the early startup
 111      code of the dynamic linker.  These flags can be used to enable
 112      early dynamic linker diagnostics to run on CPUs which are not
 113      compatible with the rest of the GNU C Library, for example, due to
 114      compiler flags which target a later instruction set architecture
 115      (ISA).
 116
 117 ‘--with-timeoutfactor=NUM’
 118      Specify an integer NUM to scale the timeout of test programs.  This
 119      factor can be changed at run time using ‘TIMEOUTFACTOR’ environment
 120      variable.
 121
 122 ‘--disable-shared’
 123      Don’t build shared libraries even if it is possible.  Not all
 124      systems support shared libraries; you need ELF support and
 125      (currently) the GNU linker.
 126
 127 ‘--disable-default-pie’
 128      Don’t build glibc programs and the testsuite as position
 129      independent executables (PIE). By default, glibc programs and tests
 130      are created as position independent executables on targets that
 131      support it.  If the toolchain and architecture support it, static
 132      executables are built as static PIE and the resulting glibc can be
 133      used with the GCC option, -static-pie, which is available with GCC
 134      8 or above, to create static PIE.
 135
 136 ‘--enable-cet’
 137 ‘--enable-cet=permissive’
 138      Enable Intel Control-flow Enforcement Technology (CET) support.
 139      When the GNU C Library is built with ‘--enable-cet’ or
 140      ‘--enable-cet=permissive’, the resulting library is protected with
 141      indirect branch tracking (IBT) and shadow stack (SHSTK).  When CET
 142      is enabled, the GNU C Library is compatible with all existing
 143      executables and shared libraries.  This feature is currently
 144      supported on i386, x86_64 and x32 with GCC 8 and binutils 2.29 or
 145      later.  Note that when CET is enabled, the GNU C Library requires
 146      CPUs capable of multi-byte NOPs, like x86-64 processors as well as
 147      Intel Pentium Pro or newer.  With ‘--enable-cet’, it is an error to
 148      dlopen a non CET enabled shared library in CET enabled application.
 149      With ‘--enable-cet=permissive’, CET is disabled when dlopening a
 150      non CET enabled shared library in CET enabled application.
 151
 152      NOTE: ‘--enable-cet’ has been tested for i686, x86_64 and x32 on
 153      non-CET processors.  ‘--enable-cet’ has been tested for i686,
 154      x86_64 and x32 on CET processors.
 155
 156 ‘--enable-memory-tagging’
 157      Enable memory tagging support if the architecture supports it.
 158      When the GNU C Library is built with this option then the resulting
 159      library will be able to control the use of tagged memory when
 160      hardware support is present by use of the tunable
 161      ‘glibc.mem.tagging’.  This includes the generation of tagged memory
 162      when using the ‘malloc’ APIs.
 163
 164      At present only AArch64 platforms with MTE provide this
 165      functionality, although the library will still operate (without
 166      memory tagging) on older versions of the architecture.
 167
 168      The default is to disable support for memory tagging.
 169
 170 ‘--disable-profile’
 171      Don’t build libraries with profiling information.  You may want to
 172      use this option if you don’t plan to do profiling.
 173
 174 ‘--enable-static-nss’
 175      Compile static versions of the NSS (Name Service Switch) libraries.
 176      This is not recommended because it defeats the purpose of NSS; a
 177      program linked statically with the NSS libraries cannot be
 178      dynamically reconfigured to use a different name database.
 179
 180 ‘--enable-hardcoded-path-in-tests’
 181      By default, dynamic tests are linked to run with the installed C
 182      library.  This option hardcodes the newly built C library path in
 183      dynamic tests so that they can be invoked directly.
 184
 185 ‘--disable-timezone-tools’
 186      By default, timezone related utilities (‘zic’, ‘zdump’, and
 187      ‘tzselect’) are installed with the GNU C Library.  If you are
 188      building these independently (e.g.  by using the ‘tzcode’ package),
 189      then this option will allow disabling the install of these.
 190
 191      Note that you need to make sure the external tools are kept in sync
 192      with the versions that the GNU C Library expects as the data
 193      formats may change over time.  Consult the ‘timezone’ subdirectory
 194      for more details.
 195
 196 ‘--enable-stack-protector’
 197 ‘--enable-stack-protector=strong’
 198 ‘--enable-stack-protector=all’
 199      Compile the C library and all other parts of the glibc package
 200      (including the threading and math libraries, NSS modules, and
 201      transliteration modules) using the GCC ‘-fstack-protector’,
 202      ‘-fstack-protector-strong’ or ‘-fstack-protector-all’ options to
 203      detect stack overruns.  Only the dynamic linker and a small number
 204      of routines called directly from assembler are excluded from this
 205      protection.
 206
 207 ‘--enable-bind-now’
 208      Disable lazy binding for installed shared objects and programs.
 209      This provides additional security hardening because it enables full
 210      RELRO and a read-only global offset table (GOT), at the cost of
 211      slightly increased program load times.
 212
 213 ‘--enable-pt_chown’
 214      The file ‘pt_chown’ is a helper binary for ‘grantpt’ (*note
 215      Pseudo-Terminals: Allocation.) that is installed setuid root to fix
 216      up pseudo-terminal ownership on GNU/Hurd.  It is not required on
 217      GNU/Linux, and the GNU C Library will not use the installed
 218      ‘pt_chown’ program when configured with ‘--enable-pt_chown’.
 219
 220 ‘--disable-werror’
 221      By default, the GNU C Library is built with ‘-Werror’.  If you wish
 222      to build without this option (for example, if building with a newer
 223      version of GCC than this version of the GNU C Library was tested
 224      with, so new warnings cause the build with ‘-Werror’ to fail), you
 225      can configure with ‘--disable-werror’.
 226
 227 ‘--disable-mathvec’
 228      By default for x86_64, the GNU C Library is built with the vector
 229      math library.  Use this option to disable the vector math library.
 230
 231 ‘--disable-scv’
 232      Disable using ‘scv’ instruction for syscalls.  All syscalls will
 233      use ‘sc’ instead, even if the kernel supports ‘scv’.  PowerPC only.
 234
 235 ‘--build=BUILD-SYSTEM’
 236 ‘--host=HOST-SYSTEM’
 237      These options are for cross-compiling.  If you specify both options
 238      and BUILD-SYSTEM is different from HOST-SYSTEM, ‘configure’ will
 239      prepare to cross-compile the GNU C Library from BUILD-SYSTEM to be
 240      used on HOST-SYSTEM.  You’ll probably need the ‘--with-headers’
 241      option too, and you may have to override CONFIGURE’s selection of
 242      the compiler and/or binutils.
 243
 244      If you only specify ‘--host’, ‘configure’ will prepare for a native
 245      compile but use what you specify instead of guessing what your
 246      system is.  This is most useful to change the CPU submodel.  For
 247      example, if ‘configure’ guesses your machine as ‘i686-pc-linux-gnu’
 248      but you want to compile a library for 586es, give
 249      ‘--host=i586-pc-linux-gnu’ or just ‘--host=i586-linux’ and add the
 250      appropriate compiler flags (‘-mcpu=i586’ will do the trick) to
 251      ‘CC’.
 252
 253      If you specify just ‘--build’, ‘configure’ will get confused.
 254
 255 ‘--with-pkgversion=VERSION’
 256      Specify a description, possibly including a build number or build
 257      date, of the binaries being built, to be included in ‘--version’
 258      output from programs installed with the GNU C Library.  For
 259      example, ‘--with-pkgversion='FooBar GNU/Linux glibc build 123'’.
 260      The default value is ‘GNU libc’.
 261
 262 ‘--with-bugurl=URL’
 263      Specify the URL that users should visit if they wish to report a
 264      bug, to be included in ‘--help’ output from programs installed with
 265      the GNU C Library.  The default value refers to the main
 266      bug-reporting information for the GNU C Library.
 267
 268 ‘--enable-fortify-source’
 269 ‘--enable-fortify-source=LEVEL’
 270      Use -D_FORTIFY_SOURCE=‘LEVEL’ to control hardening in the GNU C
 271      Library.  If not provided, ‘LEVEL’ defaults to highest possible
 272      value supported by the build compiler.
 273
 274      Default is to disable fortification.
 275
 276    To build the library and related programs, type ‘make’.  This will
 277 produce a lot of output, some of which may look like errors from ‘make’
 278 but aren’t.  Look for error messages from ‘make’ containing ‘***’.
 279 Those indicate that something is seriously wrong.
 280
 281    The compilation process can take a long time, depending on the
 282 configuration and the speed of your machine.  Some complex modules may
 283 take a very long time to compile, as much as several minutes on slower
 284 machines.  Do not panic if the compiler appears to hang.
 285
 286    If you want to run a parallel make, simply pass the ‘-j’ option with
 287 an appropriate numeric parameter to ‘make’.  You need a recent GNU
 288 ‘make’ version, though.
 289
 290    To build and run test programs which exercise some of the library
 291 facilities, type ‘make check’.  If it does not complete successfully, do
 292 not use the built library, and report a bug after verifying that the
 293 problem is not already known.  *Note Reporting Bugs::, for instructions
 294 on reporting bugs.  Note that some of the tests assume they are not
 295 being run by ‘root’.  We recommend you compile and test the GNU C
 296 Library as an unprivileged user.
 297
 298    Before reporting bugs make sure there is no problem with your system.
 299 The tests (and later installation) use some pre-existing files of the
 300 system such as ‘/etc/passwd’, ‘/etc/nsswitch.conf’ and others.  These
 301 files must all contain correct and sensible content.
 302
 303    Normally, ‘make check’ will run all the tests before reporting all
 304 problems found and exiting with error status if any problems occurred.
 305 You can specify ‘stop-on-test-failure=y’ when running ‘make check’ to
 306 make the test run stop and exit with an error status immediately when a
 307 failure occurs.
 308
 309    To format the ‘GNU C Library Reference Manual’ for printing, type
 310 ‘make dvi’.  You need a working TeX installation to do this.  The
 311 distribution builds the on-line formatted version of the manual, as Info
 312 files, as part of the build process.  You can build them manually with
 313 ‘make info’.
 314
 315    The library has a number of special-purpose configuration parameters
 316 which you can find in ‘Makeconfig’.  These can be overwritten with the
 317 file ‘configparms’.  To change them, create a ‘configparms’ in your
 318 build directory and add values as appropriate for your system.  The file
 319 is included and parsed by ‘make’ and has to follow the conventions for
 320 makefiles.
 321
 322    It is easy to configure the GNU C Library for cross-compilation by
 323 setting a few variables in ‘configparms’.  Set ‘CC’ to the
 324 cross-compiler for the target you configured the library for; it is
 325 important to use this same ‘CC’ value when running ‘configure’, like
 326 this: ‘configure TARGET CC=TARGET-gcc’.  Set ‘BUILD_CC’ to the compiler
 327 to use for programs run on the build system as part of compiling the
 328 library.  You may need to set ‘AR’ to cross-compiling versions of ‘ar’
 329 if the native tools are not configured to work with object files for the
 330 target you configured for.  When cross-compiling the GNU C Library, it
 331 may be tested using ‘make check
 332 test-wrapper="SRCDIR/scripts/cross-test-ssh.sh HOSTNAME"’, where SRCDIR
 333 is the absolute directory name for the main source directory and
 334 HOSTNAME is the host name of a system that can run the newly built
 335 binaries of the GNU C Library.  The source and build directories must be
 336 visible at the same locations on both the build system and HOSTNAME.
 337 The ‘cross-test-ssh.sh’ script requires ‘flock’ from ‘util-linux’ to
 338 work when GLIBC_TEST_ALLOW_TIME_SETTING environment variable is set.
 339
 340    It is also possible to execute tests, which require setting the date
 341 on the target machine.  Following use cases are supported:
 342    • ‘GLIBC_TEST_ALLOW_TIME_SETTING’ is set in the environment in which
 343      eligible tests are executed and have the privilege to run
 344      ‘clock_settime’.  In this case, nothing prevents those tests from
 345      running in parallel, so the caller shall assure that those tests
 346      are serialized or provide a proper wrapper script for them.
 347
 348    • The ‘cross-test-ssh.sh’ script is used and one passes the
 349      ‘--allow-time-setting’ flag.  In this case, both sets
 350      ‘GLIBC_TEST_ALLOW_TIME_SETTING’ and serialization of test execution
 351      are assured automatically.
 352
 353    In general, when testing the GNU C Library, ‘test-wrapper’ may be set
 354 to the name and arguments of any program to run newly built binaries.
 355 This program must preserve the arguments to the binary being run, its
 356 working directory and the standard input, output and error file
 357 descriptors.  If ‘TEST-WRAPPER env’ will not work to run a program with
 358 environment variables set, then ‘test-wrapper-env’ must be set to a
 359 program that runs a newly built program with environment variable
 360 assignments in effect, those assignments being specified as ‘VAR=VALUE’
 361 before the name of the program to be run.  If multiple assignments to
 362 the same variable are specified, the last assignment specified must take
 363 precedence.  Similarly, if ‘TEST-WRAPPER env -i’ will not work to run a
 364 program with an environment completely empty of variables except those
 365 directly assigned, then ‘test-wrapper-env-only’ must be set; its use has
 366 the same syntax as ‘test-wrapper-env’, the only difference in its
 367 semantics being starting with an empty set of environment variables
 368 rather than the ambient set.
 369
 370    For AArch64 with SVE, when testing the GNU C Library, ‘test-wrapper’
 371 may be set to "SRCDIR/sysdeps/unix/sysv/linux/aarch64/vltest.py
 372 VECTOR-LENGTH" to change Vector Length.
 373
 374 Installing the C Library
 375 ========================
 376
 377 To install the library and its header files, and the Info files of the
 378 manual, type ‘make install’.  This will build things, if necessary,
 379 before installing them; however, you should still compile everything
 380 first.  If you are installing the GNU C Library as your primary C
 381 library, we recommend that you shut the system down to single-user mode
 382 first, and reboot afterward.  This minimizes the risk of breaking things
 383 when the library changes out from underneath.
 384
 385    ‘make install’ will do the entire job of upgrading from a previous
 386 installation of the GNU C Library version 2.x.  There may sometimes be
 387 headers left behind from the previous installation, but those are
 388 generally harmless.  If you want to avoid leaving headers behind you can
 389 do things in the following order.
 390
 391    You must first build the library (‘make’), optionally check it (‘make
 392 check’), switch the include directories and then install (‘make
 393 install’).  The steps must be done in this order.  Not moving the
 394 directory before install will result in an unusable mixture of header
 395 files from both libraries, but configuring, building, and checking the
 396 library requires the ability to compile and run programs against the old
 397 library.  The new ‘/usr/include’, after switching the include
 398 directories and before installing the library should contain the Linux
 399 headers, but nothing else.  If you do this, you will need to restore any
 400 headers from libraries other than the GNU C Library yourself after
 401 installing the library.
 402
 403    You can install the GNU C Library somewhere other than where you
 404 configured it to go by setting the ‘DESTDIR’ GNU standard make variable
 405 on the command line for ‘make install’.  The value of this variable is
 406 prepended to all the paths for installation.  This is useful when
 407 setting up a chroot environment or preparing a binary distribution.  The
 408 directory should be specified with an absolute file name.  Installing
 409 with the ‘prefix’ and ‘exec_prefix’ GNU standard make variables set is
 410 not supported.
 411
 412    The GNU C Library includes a daemon called ‘nscd’, which you may or
 413 may not want to run.  ‘nscd’ caches name service lookups; it can
 414 dramatically improve performance with NIS+, and may help with DNS as
 415 well.
 416
 417    One auxiliary program, ‘/usr/libexec/pt_chown’, is installed setuid
 418 ‘root’ if the ‘--enable-pt_chown’ configuration option is used.  This
 419 program is invoked by the ‘grantpt’ function; it sets the permissions on
 420 a pseudoterminal so it can be used by the calling process.  If you are
 421 using a Linux kernel with the ‘devpts’ filesystem enabled and mounted at
 422 ‘/dev/pts’, you don’t need this program.
 423
 424    After installation you should configure the timezone and install
 425 locales for your system.  The time zone configuration ensures that your
 426 system time matches the time for your current timezone.  The locales
 427 ensure that the display of information on your system matches the
 428 expectations of your language and geographic region.
 429
 430    The GNU C Library is able to use two kinds of localization
 431 information sources, the first is a locale database named
 432 ‘locale-archive’ which is generally installed as
 433 ‘/usr/lib/locale/locale-archive’.  The locale archive has the benefit of
 434 taking up less space and being very fast to load, but only if you plan
 435 to install sixty or more locales.  If you plan to install one or two
 436 locales you can instead install individual locales into their self-named
 437 directories e.g. ‘/usr/lib/locale/en_US.utf8’.  For example to install
 438 the German locale using the character set for UTF-8 with name ‘de_DE’
 439 into the locale archive issue the command ‘localedef -i de_DE -f UTF-8
 440 de_DE’, and to install just the one locale issue the command ‘localedef
 441 --no-archive -i de_DE -f UTF-8 de_DE’.  To configure all locales that
 442 are supported by the GNU C Library, you can issue from your build
 443 directory the command ‘make localedata/install-locales’ to install all
 444 locales into the locale archive or ‘make
 445 localedata/install-locale-files’ to install all locales as files in the
 446 default configured locale installation directory (derived from
 447 ‘--prefix’ or ‘--localedir’).  To install into an alternative system
 448 root use ‘DESTDIR’ e.g. ‘make localedata/install-locale-files
 449 DESTDIR=/opt/glibc’, but note that this does not change the configured
 450 prefix.
 451
 452    To configure the locally used timezone, set the ‘TZ’ environment
 453 variable.  The script ‘tzselect’ helps you to select the right value.
 454 As an example, for Germany, ‘tzselect’ would tell you to use
 455 ‘TZ='Europe/Berlin'’.  For a system wide installation (the given paths
 456 are for an installation with ‘--prefix=/usr’), link the timezone file
 457 which is in ‘/usr/share/zoneinfo’ to the file ‘/etc/localtime’.  For
 458 Germany, you might execute ‘ln -s /usr/share/zoneinfo/Europe/Berlin
 459 /etc/localtime’.
 460
 461 Recommended Tools for Compilation
 462 =================================
 463
 464 We recommend installing the following GNU tools before attempting to
 465 build the GNU C Library:
 466
 467    • GNU ‘make’ 4.0 or newer
 468
 469      As of release time, GNU ‘make’ 4.4 is the newest verified to work
 470      to build the GNU C Library.
 471
 472    • GCC 6.2 or newer
 473
 474      GCC 6.2 or higher is required.  In general it is recommended to use
 475      the newest version of the compiler that is known to work for
 476      building the GNU C Library, as newer compilers usually produce
 477      better code.  As of release time, GCC 13.2 is the newest compiler
 478      verified to work to build the GNU C Library.
 479
 480      For PowerPC 64-bits little-endian (powerpc64le), a GCC version with
 481      support for ‘-mno-gnu-attribute’, ‘-mabi=ieeelongdouble’, and
 482      ‘-mabi=ibmlondouble’ is required.  Likewise, the compiler must also
 483      support passing ‘-mlong-double-128’ with the preceding options.  As
 484      of release, this implies GCC 7.4 and newer (excepting GCC 7.5.0,
 485      see GCC PR94200).  These additional features are required for
 486      building the GNU C Library with support for IEEE long double.
 487
 488      For ARC architecture builds, GCC 8.3 or higher is needed.
 489
 490      For s390x architecture builds, GCC 7.1 or higher is needed (See gcc
 491      Bug 98269).
 492
 493      For AArch64 architecture builds with mathvec enabled, GCC 10 or
 494      higher is needed due to dependency on arm_sve.h.
 495
 496      For multi-arch support it is recommended to use a GCC which has
 497      been built with support for GNU indirect functions.  This ensures
 498      that correct debugging information is generated for functions
 499      selected by IFUNC resolvers.  This support can either be enabled by
 500      configuring GCC with ‘--enable-gnu-indirect-function’, or by
 501      enabling it by default by setting ‘default_gnu_indirect_function’
 502      variable for a particular architecture in the GCC source file
 503      ‘gcc/config.gcc’.
 504
 505      You can use whatever compiler you like to compile programs that use
 506      the GNU C Library.
 507
 508      Check the FAQ for any special compiler issues on particular
 509      platforms.
 510
 511    • GNU ‘binutils’ 2.25 or later
 512
 513      You must use GNU ‘binutils’ (as and ld) to build the GNU C Library.
 514      No other assembler or linker has the necessary functionality at the
 515      moment.  As of release time, GNU ‘binutils’ 2.41 is the newest
 516      verified to work to build the GNU C Library.
 517
 518      For PowerPC 64-bits little-endian (powerpc64le), ‘objcopy’ is
 519      required to support ‘--update-section’.  This option requires
 520      binutils 2.26 or newer.
 521
 522      ARC architecture needs ‘binutils’ 2.32 or higher for TLS related
 523      fixes.
 524
 525    • GNU ‘texinfo’ 4.7 or later
 526
 527      To correctly translate and install the Texinfo documentation you
 528      need this version of the ‘texinfo’ package.  Earlier versions do
 529      not understand all the tags used in the document, and the
 530      installation mechanism for the info files is not present or works
 531      differently.  As of release time, ‘texinfo’ 7.0.3 is the newest
 532      verified to work to build the GNU C Library.
 533
 534    • GNU ‘awk’ 3.1.2, or higher
 535
 536      ‘awk’ is used in several places to generate files.  Some ‘gawk’
 537      extensions are used, including the ‘asorti’ function, which was
 538      introduced in version 3.1.2 of ‘gawk’.  As of release time, ‘gawk’
 539      version 5.2.2 is the newest verified to work to build the GNU C
 540      Library.
 541
 542    • GNU ‘bison’ 2.7 or later
 543
 544      ‘bison’ is used to generate the ‘yacc’ parser code in the ‘intl’
 545      subdirectory.  As of release time, ‘bison’ version 3.8.2 is the
 546      newest verified to work to build the GNU C Library.
 547
 548    • Perl 5
 549
 550      Perl is not required, but if present it is used in some tests and
 551      the ‘mtrace’ program, to build the GNU C Library manual.  As of
 552      release time ‘perl’ version 5.38.0 is the newest verified to work
 553      to build the GNU C Library.
 554
 555    • GNU ‘sed’ 3.02 or newer
 556
 557      ‘Sed’ is used in several places to generate files.  Most scripts
 558      work with any version of ‘sed’.  As of release time, ‘sed’ version
 559      4.9 is the newest verified to work to build the GNU C Library.
 560
 561    • Python 3.4 or later
 562
 563      Python is required to build the GNU C Library.  As of release time,
 564      Python 3.11 is the newest verified to work for building and testing
 565      the GNU C Library.
 566
 567    • PExpect 4.0
 568
 569      The pretty printer tests drive GDB through test programs and
 570      compare its output to the printers’.  PExpect is used to capture
 571      the output of GDB, and should be compatible with the Python version
 572      in your system.  As of release time PExpect 4.8.0 is the newest
 573      verified to work to test the pretty printers.
 574
 575    • The Python ‘abnf’ module.
 576
 577      This module is optional and used to verify some ABNF grammars in
 578      the manual.  Version 2.2.0 has been confirmed to work as expected.
 579      A missing ‘abnf’ module does not reduce the test coverage of the
 580      library itself.
 581
 582    • GDB 7.8 or later with support for Python 2.7/3.4 or later
 583
 584      GDB itself needs to be configured with Python support in order to
 585      use the pretty printers.  Notice that your system having Python
 586      available doesn’t imply that GDB supports it, nor that your
 587      system’s Python and GDB’s have the same version.  As of release
 588      time GNU ‘debugger’ 13.2 is the newest verified to work to test the
 589      pretty printers.
 590
 591      Unless Python, PExpect and GDB with Python support are present, the
 592      printer tests will report themselves as ‘UNSUPPORTED’.  Notice that
 593      some of the printer tests require the GNU C Library to be compiled
 594      with debugging symbols.
 595
 596 If you change any of the ‘configure.ac’ files you will also need
 597
 598    • GNU ‘autoconf’ 2.71 (exactly)
 599
 600 and if you change any of the message translation files you will need
 601
 602    • GNU ‘gettext’ 0.10.36 or later
 603
 604      As of release time, GNU ‘gettext’ version 0.21.1 is the newest
 605      version verified to work to build the GNU C Library.
 606
 607 You may also need these packages if you upgrade your source tree using
 608 patches, although we try to avoid this.
 609
 610 Specific advice for GNU/Linux systems
 611 =====================================
 612
 613 If you are installing the GNU C Library on GNU/Linux systems, you need
 614 to have the header files from a 3.2 or newer kernel around for
 615 reference.  (For the ia64 architecture, you need version 3.2.18 or newer
 616 because this is the first version with support for the ‘accept4’ system
 617 call.)  These headers must be installed using ‘make headers_install’;
 618 the headers present in the kernel source directory are not suitable for
 619 direct use by the GNU C Library.  You do not need to use that kernel,
 620 just have its headers installed where the GNU C Library can access them,
 621 referred to here as INSTALL-DIRECTORY.  The easiest way to do this is to
 622 unpack it in a directory such as ‘/usr/src/linux-VERSION’.  In that
 623 directory, run ‘make headers_install
 624 INSTALL_HDR_PATH=INSTALL-DIRECTORY’.  Finally, configure the GNU C
 625 Library with the option ‘--with-headers=INSTALL-DIRECTORY/include’.  Use
 626 the most recent kernel you can get your hands on.  (If you are
 627 cross-compiling the GNU C Library, you need to specify
 628 ‘ARCH=ARCHITECTURE’ in the ‘make headers_install’ command, where
 629 ARCHITECTURE is the architecture name used by the Linux kernel, such as
 630 ‘x86’ or ‘powerpc’.)
 631
 632    After installing the GNU C Library, you may need to remove or rename
 633 directories such as ‘/usr/include/linux’ and ‘/usr/include/asm’, and
 634 replace them with copies of directories such as ‘linux’ and ‘asm’ from
 635 ‘INSTALL-DIRECTORY/include’.  All directories present in
 636 ‘INSTALL-DIRECTORY/include’ should be copied, except that the GNU C
 637 Library provides its own version of ‘/usr/include/scsi’; the files
 638 provided by the kernel should be copied without replacing those provided
 639 by the GNU C Library.  The ‘linux’, ‘asm’ and ‘asm-generic’ directories
 640 are required to compile programs using the GNU C Library; the other
 641 directories describe interfaces to the kernel but are not required if
 642 not compiling programs using those interfaces.  You do not need to copy
 643 kernel headers if you did not specify an alternate kernel header source
 644 using ‘--with-headers’.
 645
 646    The Filesystem Hierarchy Standard for GNU/Linux systems expects some
 647 components of the GNU C Library installation to be in ‘/lib’ and some in
 648 ‘/usr/lib’.  This is handled automatically if you configure the GNU C
 649 Library with ‘--prefix=/usr’.  If you set some other prefix or allow it
 650 to default to ‘/usr/local’, then all the components are installed there.
 651
 652    As of release time, Linux version 6.1.5 is the newest stable version
 653 verified to work to build the GNU C Library.
 654
 655 Reporting Bugs
 656 ==============
 657
 658 There are probably bugs in the GNU C Library.  There are certainly
 659 errors and omissions in this manual.  If you report them, they will get
 660 fixed.  If you don’t, no one will ever know about them and they will
 661 remain unfixed for all eternity, if not longer.
 662
 663    It is a good idea to verify that the problem has not already been
 664 reported.  Bugs are documented in two places: The file ‘BUGS’ describes
 665 a number of well known bugs and the central GNU C Library bug tracking
 666 system has a WWW interface at <https://sourceware.org/bugzilla/>.  The
 667 WWW interface gives you access to open and closed reports.  A closed
 668 report normally includes a patch or a hint on solving the problem.
 669
 670    To report a bug, first you must find it.  With any luck, this will be
 671 the hard part.  Once you’ve found a bug, make sure it’s really a bug.  A
 672 good way to do this is to see if the GNU C Library behaves the same way
 673 some other C library does.  If so, probably you are wrong and the
 674 libraries are right (but not necessarily).  If not, one of the libraries
 675 is probably wrong.  It might not be the GNU C Library.  Many historical
 676 Unix C libraries permit things that we don’t, such as closing a file
 677 twice.
 678
 679    If you think you have found some way in which the GNU C Library does
 680 not conform to the ISO and POSIX standards (*note Standards and
 681 Portability::), that is definitely a bug.  Report it!
 682
 683    Once you’re sure you’ve found a bug, try to narrow it down to the
 684 smallest test case that reproduces the problem.  In the case of a C
 685 library, you really only need to narrow it down to one library function
 686 call, if possible.  This should not be too difficult.
 687
 688    The final step when you have a simple test case is to report the bug.
 689 Do this at <https://www.gnu.org/software/libc/bugs.html>.
 690
 691    If you are not sure how a function should behave, and this manual
 692 doesn’t tell you, that’s a bug in the manual.  Report that too!  If the
 693 function’s behavior disagrees with the manual, then either the library
 694 or the manual has a bug, so report the disagreement.  If you find any
 695 errors or omissions in this manual, please report them to the bug
 696 database.  If you refer to specific sections of the manual, please
 697 include the section names for easier identification.