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 ‘--enable-crypt’
 232      Install the legacy passphrase-hashing library ‘libcrypt’ and the
 233      header file ‘crypt.h’.  ‘unistd.h’ will declare the function
 234      ‘crypt’ regardless of this option.  Using this option does not
 235      change the set of programs that may need to be linked with
 236      ‘-lcrypt’; it only means that the GNU C Library will provide that
 237      library.
 238
 239      This option is for hackers and distributions who may not yet be
 240      able to use libcrypt alternatives such as libxcrypt and need this
 241      legacy implementation as a temporary workaround.  Note that
 242      libcrypt may be removed in a future release.
 243
 244 ‘--disable-scv’
 245      Disable using ‘scv’ instruction for syscalls.  All syscalls will
 246      use ‘sc’ instead, even if the kernel supports ‘scv’.  PowerPC only.
 247
 248 ‘--build=BUILD-SYSTEM’
 249 ‘--host=HOST-SYSTEM’
 250      These options are for cross-compiling.  If you specify both options
 251      and BUILD-SYSTEM is different from HOST-SYSTEM, ‘configure’ will
 252      prepare to cross-compile the GNU C Library from BUILD-SYSTEM to be
 253      used on HOST-SYSTEM.  You’ll probably need the ‘--with-headers’
 254      option too, and you may have to override CONFIGURE’s selection of
 255      the compiler and/or binutils.
 256
 257      If you only specify ‘--host’, ‘configure’ will prepare for a native
 258      compile but use what you specify instead of guessing what your
 259      system is.  This is most useful to change the CPU submodel.  For
 260      example, if ‘configure’ guesses your machine as ‘i686-pc-linux-gnu’
 261      but you want to compile a library for 586es, give
 262      ‘--host=i586-pc-linux-gnu’ or just ‘--host=i586-linux’ and add the
 263      appropriate compiler flags (‘-mcpu=i586’ will do the trick) to
 264      ‘CC’.
 265
 266      If you specify just ‘--build’, ‘configure’ will get confused.
 267
 268 ‘--with-pkgversion=VERSION’
 269      Specify a description, possibly including a build number or build
 270      date, of the binaries being built, to be included in ‘--version’
 271      output from programs installed with the GNU C Library.  For
 272      example, ‘--with-pkgversion='FooBar GNU/Linux glibc build 123'’.
 273      The default value is ‘GNU libc’.
 274
 275 ‘--with-bugurl=URL’
 276      Specify the URL that users should visit if they wish to report a
 277      bug, to be included in ‘--help’ output from programs installed with
 278      the GNU C Library.  The default value refers to the main
 279      bug-reporting information for the GNU C Library.
 280
 281 ‘--enable-fortify-source’
 282 ‘--enable-fortify-source=LEVEL’
 283      Use -D_FORTIFY_SOURCE=‘LEVEL’ to control hardening in the GNU C
 284      Library.  If not provided, ‘LEVEL’ defaults to highest possible
 285      value supported by the build compiler.
 286
 287      Default is to disable fortification.
 288
 289    To build the library and related programs, type ‘make’.  This will
 290 produce a lot of output, some of which may look like errors from ‘make’
 291 but aren’t.  Look for error messages from ‘make’ containing ‘***’.
 292 Those indicate that something is seriously wrong.
 293
 294    The compilation process can take a long time, depending on the
 295 configuration and the speed of your machine.  Some complex modules may
 296 take a very long time to compile, as much as several minutes on slower
 297 machines.  Do not panic if the compiler appears to hang.
 298
 299    If you want to run a parallel make, simply pass the ‘-j’ option with
 300 an appropriate numeric parameter to ‘make’.  You need a recent GNU
 301 ‘make’ version, though.
 302
 303    To build and run test programs which exercise some of the library
 304 facilities, type ‘make check’.  If it does not complete successfully, do
 305 not use the built library, and report a bug after verifying that the
 306 problem is not already known.  *Note Reporting Bugs::, for instructions
 307 on reporting bugs.  Note that some of the tests assume they are not
 308 being run by ‘root’.  We recommend you compile and test the GNU C
 309 Library as an unprivileged user.
 310
 311    Before reporting bugs make sure there is no problem with your system.
 312 The tests (and later installation) use some pre-existing files of the
 313 system such as ‘/etc/passwd’, ‘/etc/nsswitch.conf’ and others.  These
 314 files must all contain correct and sensible content.
 315
 316    Normally, ‘make check’ will run all the tests before reporting all
 317 problems found and exiting with error status if any problems occurred.
 318 You can specify ‘stop-on-test-failure=y’ when running ‘make check’ to
 319 make the test run stop and exit with an error status immediately when a
 320 failure occurs.
 321
 322    To format the ‘GNU C Library Reference Manual’ for printing, type
 323 ‘make dvi’.  You need a working TeX installation to do this.  The
 324 distribution builds the on-line formatted version of the manual, as Info
 325 files, as part of the build process.  You can build them manually with
 326 ‘make info’.
 327
 328    The library has a number of special-purpose configuration parameters
 329 which you can find in ‘Makeconfig’.  These can be overwritten with the
 330 file ‘configparms’.  To change them, create a ‘configparms’ in your
 331 build directory and add values as appropriate for your system.  The file
 332 is included and parsed by ‘make’ and has to follow the conventions for
 333 makefiles.
 334
 335    It is easy to configure the GNU C Library for cross-compilation by
 336 setting a few variables in ‘configparms’.  Set ‘CC’ to the
 337 cross-compiler for the target you configured the library for; it is
 338 important to use this same ‘CC’ value when running ‘configure’, like
 339 this: ‘configure TARGET CC=TARGET-gcc’.  Set ‘BUILD_CC’ to the compiler
 340 to use for programs run on the build system as part of compiling the
 341 library.  You may need to set ‘AR’ to cross-compiling versions of ‘ar’
 342 if the native tools are not configured to work with object files for the
 343 target you configured for.  When cross-compiling the GNU C Library, it
 344 may be tested using ‘make check
 345 test-wrapper="SRCDIR/scripts/cross-test-ssh.sh HOSTNAME"’, where SRCDIR
 346 is the absolute directory name for the main source directory and
 347 HOSTNAME is the host name of a system that can run the newly built
 348 binaries of the GNU C Library.  The source and build directories must be
 349 visible at the same locations on both the build system and HOSTNAME.
 350 The ‘cross-test-ssh.sh’ script requires ‘flock’ from ‘util-linux’ to
 351 work when GLIBC_TEST_ALLOW_TIME_SETTING environment variable is set.
 352
 353    It is also possible to execute tests, which require setting the date
 354 on the target machine.  Following use cases are supported:
 355    • ‘GLIBC_TEST_ALLOW_TIME_SETTING’ is set in the environment in which
 356      eligible tests are executed and have the privilege to run
 357      ‘clock_settime’.  In this case, nothing prevents those tests from
 358      running in parallel, so the caller shall assure that those tests
 359      are serialized or provide a proper wrapper script for them.
 360
 361    • The ‘cross-test-ssh.sh’ script is used and one passes the
 362      ‘--allow-time-setting’ flag.  In this case, both sets
 363      ‘GLIBC_TEST_ALLOW_TIME_SETTING’ and serialization of test execution
 364      are assured automatically.
 365
 366    In general, when testing the GNU C Library, ‘test-wrapper’ may be set
 367 to the name and arguments of any program to run newly built binaries.
 368 This program must preserve the arguments to the binary being run, its
 369 working directory and the standard input, output and error file
 370 descriptors.  If ‘TEST-WRAPPER env’ will not work to run a program with
 371 environment variables set, then ‘test-wrapper-env’ must be set to a
 372 program that runs a newly built program with environment variable
 373 assignments in effect, those assignments being specified as ‘VAR=VALUE’
 374 before the name of the program to be run.  If multiple assignments to
 375 the same variable are specified, the last assignment specified must take
 376 precedence.  Similarly, if ‘TEST-WRAPPER env -i’ will not work to run a
 377 program with an environment completely empty of variables except those
 378 directly assigned, then ‘test-wrapper-env-only’ must be set; its use has
 379 the same syntax as ‘test-wrapper-env’, the only difference in its
 380 semantics being starting with an empty set of environment variables
 381 rather than the ambient set.
 382
 383    For AArch64 with SVE, when testing the GNU C Library, ‘test-wrapper’
 384 may be set to "SRCDIR/sysdeps/unix/sysv/linux/aarch64/vltest.py
 385 VECTOR-LENGTH" to change Vector Length.
 386
 387 Installing the C Library
 388 ========================
 389
 390 To install the library and its header files, and the Info files of the
 391 manual, type ‘make install’.  This will build things, if necessary,
 392 before installing them; however, you should still compile everything
 393 first.  If you are installing the GNU C Library as your primary C
 394 library, we recommend that you shut the system down to single-user mode
 395 first, and reboot afterward.  This minimizes the risk of breaking things
 396 when the library changes out from underneath.
 397
 398    ‘make install’ will do the entire job of upgrading from a previous
 399 installation of the GNU C Library version 2.x.  There may sometimes be
 400 headers left behind from the previous installation, but those are
 401 generally harmless.  If you want to avoid leaving headers behind you can
 402 do things in the following order.
 403
 404    You must first build the library (‘make’), optionally check it (‘make
 405 check’), switch the include directories and then install (‘make
 406 install’).  The steps must be done in this order.  Not moving the
 407 directory before install will result in an unusable mixture of header
 408 files from both libraries, but configuring, building, and checking the
 409 library requires the ability to compile and run programs against the old
 410 library.  The new ‘/usr/include’, after switching the include
 411 directories and before installing the library should contain the Linux
 412 headers, but nothing else.  If you do this, you will need to restore any
 413 headers from libraries other than the GNU C Library yourself after
 414 installing the library.
 415
 416    You can install the GNU C Library somewhere other than where you
 417 configured it to go by setting the ‘DESTDIR’ GNU standard make variable
 418 on the command line for ‘make install’.  The value of this variable is
 419 prepended to all the paths for installation.  This is useful when
 420 setting up a chroot environment or preparing a binary distribution.  The
 421 directory should be specified with an absolute file name.  Installing
 422 with the ‘prefix’ and ‘exec_prefix’ GNU standard make variables set is
 423 not supported.
 424
 425    The GNU C Library includes a daemon called ‘nscd’, which you may or
 426 may not want to run.  ‘nscd’ caches name service lookups; it can
 427 dramatically improve performance with NIS+, and may help with DNS as
 428 well.
 429
 430    One auxiliary program, ‘/usr/libexec/pt_chown’, is installed setuid
 431 ‘root’ if the ‘--enable-pt_chown’ configuration option is used.  This
 432 program is invoked by the ‘grantpt’ function; it sets the permissions on
 433 a pseudoterminal so it can be used by the calling process.  If you are
 434 using a Linux kernel with the ‘devpts’ filesystem enabled and mounted at
 435 ‘/dev/pts’, you don’t need this program.
 436
 437    After installation you should configure the timezone and install
 438 locales for your system.  The time zone configuration ensures that your
 439 system time matches the time for your current timezone.  The locales
 440 ensure that the display of information on your system matches the
 441 expectations of your language and geographic region.
 442
 443    The GNU C Library is able to use two kinds of localization
 444 information sources, the first is a locale database named
 445 ‘locale-archive’ which is generally installed as
 446 ‘/usr/lib/locale/locale-archive’.  The locale archive has the benefit of
 447 taking up less space and being very fast to load, but only if you plan
 448 to install sixty or more locales.  If you plan to install one or two
 449 locales you can instead install individual locales into their self-named
 450 directories e.g. ‘/usr/lib/locale/en_US.utf8’.  For example to install
 451 the German locale using the character set for UTF-8 with name ‘de_DE’
 452 into the locale archive issue the command ‘localedef -i de_DE -f UTF-8
 453 de_DE’, and to install just the one locale issue the command ‘localedef
 454 --no-archive -i de_DE -f UTF-8 de_DE’.  To configure all locales that
 455 are supported by the GNU C Library, you can issue from your build
 456 directory the command ‘make localedata/install-locales’ to install all
 457 locales into the locale archive or ‘make
 458 localedata/install-locale-files’ to install all locales as files in the
 459 default configured locale installation directory (derived from
 460 ‘--prefix’ or ‘--localedir’).  To install into an alternative system
 461 root use ‘DESTDIR’ e.g. ‘make localedata/install-locale-files
 462 DESTDIR=/opt/glibc’, but note that this does not change the configured
 463 prefix.
 464
 465    To configure the locally used timezone, set the ‘TZ’ environment
 466 variable.  The script ‘tzselect’ helps you to select the right value.
 467 As an example, for Germany, ‘tzselect’ would tell you to use
 468 ‘TZ='Europe/Berlin'’.  For a system wide installation (the given paths
 469 are for an installation with ‘--prefix=/usr’), link the timezone file
 470 which is in ‘/usr/share/zoneinfo’ to the file ‘/etc/localtime’.  For
 471 Germany, you might execute ‘ln -s /usr/share/zoneinfo/Europe/Berlin
 472 /etc/localtime’.
 473
 474 Recommended Tools for Compilation
 475 =================================
 476
 477 We recommend installing the following GNU tools before attempting to
 478 build the GNU C Library:
 479
 480    • GNU ‘make’ 4.0 or newer
 481
 482      As of release time, GNU ‘make’ 4.4 is the newest verified to work
 483      to build the GNU C Library.
 484
 485    • GCC 6.2 or newer
 486
 487      GCC 6.2 or higher is required.  In general it is recommended to use
 488      the newest version of the compiler that is known to work for
 489      building the GNU C Library, as newer compilers usually produce
 490      better code.  As of release time, GCC 13.2 is the newest compiler
 491      verified to work to build the GNU C Library.
 492
 493      For PowerPC 64-bits little-endian (powerpc64le), a GCC version with
 494      support for ‘-mno-gnu-attribute’, ‘-mabi=ieeelongdouble’, and
 495      ‘-mabi=ibmlondouble’ is required.  Likewise, the compiler must also
 496      support passing ‘-mlong-double-128’ with the preceding options.  As
 497      of release, this implies GCC 7.4 and newer (excepting GCC 7.5.0,
 498      see GCC PR94200).  These additional features are required for
 499      building the GNU C Library with support for IEEE long double.
 500
 501      For ARC architecture builds, GCC 8.3 or higher is needed.
 502
 503      For s390x architecture builds, GCC 7.1 or higher is needed (See gcc
 504      Bug 98269).
 505
 506      For AArch64 architecture builds with mathvec enabled, GCC 10 or
 507      higher is needed due to dependency on arm_sve.h.
 508
 509      For multi-arch support it is recommended to use a GCC which has
 510      been built with support for GNU indirect functions.  This ensures
 511      that correct debugging information is generated for functions
 512      selected by IFUNC resolvers.  This support can either be enabled by
 513      configuring GCC with ‘--enable-gnu-indirect-function’, or by
 514      enabling it by default by setting ‘default_gnu_indirect_function’
 515      variable for a particular architecture in the GCC source file
 516      ‘gcc/config.gcc’.
 517
 518      You can use whatever compiler you like to compile programs that use
 519      the GNU C Library.
 520
 521      Check the FAQ for any special compiler issues on particular
 522      platforms.
 523
 524    • GNU ‘binutils’ 2.25 or later
 525
 526      You must use GNU ‘binutils’ (as and ld) to build the GNU C Library.
 527      No other assembler or linker has the necessary functionality at the
 528      moment.  As of release time, GNU ‘binutils’ 2.41 is the newest
 529      verified to work to build the GNU C Library.
 530
 531      For PowerPC 64-bits little-endian (powerpc64le), ‘objcopy’ is
 532      required to support ‘--update-section’.  This option requires
 533      binutils 2.26 or newer.
 534
 535      ARC architecture needs ‘binutils’ 2.32 or higher for TLS related
 536      fixes.
 537
 538    • GNU ‘texinfo’ 4.7 or later
 539
 540      To correctly translate and install the Texinfo documentation you
 541      need this version of the ‘texinfo’ package.  Earlier versions do
 542      not understand all the tags used in the document, and the
 543      installation mechanism for the info files is not present or works
 544      differently.  As of release time, ‘texinfo’ 7.0.3 is the newest
 545      verified to work to build the GNU C Library.
 546
 547    • GNU ‘awk’ 3.1.2, or higher
 548
 549      ‘awk’ is used in several places to generate files.  Some ‘gawk’
 550      extensions are used, including the ‘asorti’ function, which was
 551      introduced in version 3.1.2 of ‘gawk’.  As of release time, ‘gawk’
 552      version 5.2.2 is the newest verified to work to build the GNU C
 553      Library.
 554
 555    • GNU ‘bison’ 2.7 or later
 556
 557      ‘bison’ is used to generate the ‘yacc’ parser code in the ‘intl’
 558      subdirectory.  As of release time, ‘bison’ version 3.8.2 is the
 559      newest verified to work to build the GNU C Library.
 560
 561    • Perl 5
 562
 563      Perl is not required, but if present it is used in some tests and
 564      the ‘mtrace’ program, to build the GNU C Library manual.  As of
 565      release time ‘perl’ version 5.38.0 is the newest verified to work
 566      to build the GNU C Library.
 567
 568    • GNU ‘sed’ 3.02 or newer
 569
 570      ‘Sed’ is used in several places to generate files.  Most scripts
 571      work with any version of ‘sed’.  As of release time, ‘sed’ version
 572      4.9 is the newest verified to work to build the GNU C Library.
 573
 574    • Python 3.4 or later
 575
 576      Python is required to build the GNU C Library.  As of release time,
 577      Python 3.11 is the newest verified to work for building and testing
 578      the GNU C Library.
 579
 580    • PExpect 4.0
 581
 582      The pretty printer tests drive GDB through test programs and
 583      compare its output to the printers’.  PExpect is used to capture
 584      the output of GDB, and should be compatible with the Python version
 585      in your system.  As of release time PExpect 4.8.0 is the newest
 586      verified to work to test the pretty printers.
 587
 588    • The Python ‘abnf’ module.
 589
 590      This module is optional and used to verify some ABNF grammars in
 591      the manual.  Version 2.2.0 has been confirmed to work as expected.
 592      A missing ‘abnf’ module does not reduce the test coverage of the
 593      library itself.
 594
 595    • GDB 7.8 or later with support for Python 2.7/3.4 or later
 596
 597      GDB itself needs to be configured with Python support in order to
 598      use the pretty printers.  Notice that your system having Python
 599      available doesn’t imply that GDB supports it, nor that your
 600      system’s Python and GDB’s have the same version.  As of release
 601      time GNU ‘debugger’ 13.2 is the newest verified to work to test the
 602      pretty printers.
 603
 604      Unless Python, PExpect and GDB with Python support are present, the
 605      printer tests will report themselves as ‘UNSUPPORTED’.  Notice that
 606      some of the printer tests require the GNU C Library to be compiled
 607      with debugging symbols.
 608
 609 If you change any of the ‘configure.ac’ files you will also need
 610
 611    • GNU ‘autoconf’ 2.71 (exactly)
 612
 613 and if you change any of the message translation files you will need
 614
 615    • GNU ‘gettext’ 0.10.36 or later
 616
 617      As of release time, GNU ‘gettext’ version 0.21.1 is the newest
 618      version verified to work to build the GNU C Library.
 619
 620 You may also need these packages if you upgrade your source tree using
 621 patches, although we try to avoid this.
 622
 623 Specific advice for GNU/Linux systems
 624 =====================================
 625
 626 If you are installing the GNU C Library on GNU/Linux systems, you need
 627 to have the header files from a 3.2 or newer kernel around for
 628 reference.  (For the ia64 architecture, you need version 3.2.18 or newer
 629 because this is the first version with support for the ‘accept4’ system
 630 call.)  These headers must be installed using ‘make headers_install’;
 631 the headers present in the kernel source directory are not suitable for
 632 direct use by the GNU C Library.  You do not need to use that kernel,
 633 just have its headers installed where the GNU C Library can access them,
 634 referred to here as INSTALL-DIRECTORY.  The easiest way to do this is to
 635 unpack it in a directory such as ‘/usr/src/linux-VERSION’.  In that
 636 directory, run ‘make headers_install
 637 INSTALL_HDR_PATH=INSTALL-DIRECTORY’.  Finally, configure the GNU C
 638 Library with the option ‘--with-headers=INSTALL-DIRECTORY/include’.  Use
 639 the most recent kernel you can get your hands on.  (If you are
 640 cross-compiling the GNU C Library, you need to specify
 641 ‘ARCH=ARCHITECTURE’ in the ‘make headers_install’ command, where
 642 ARCHITECTURE is the architecture name used by the Linux kernel, such as
 643 ‘x86’ or ‘powerpc’.)
 644
 645    After installing the GNU C Library, you may need to remove or rename
 646 directories such as ‘/usr/include/linux’ and ‘/usr/include/asm’, and
 647 replace them with copies of directories such as ‘linux’ and ‘asm’ from
 648 ‘INSTALL-DIRECTORY/include’.  All directories present in
 649 ‘INSTALL-DIRECTORY/include’ should be copied, except that the GNU C
 650 Library provides its own version of ‘/usr/include/scsi’; the files
 651 provided by the kernel should be copied without replacing those provided
 652 by the GNU C Library.  The ‘linux’, ‘asm’ and ‘asm-generic’ directories
 653 are required to compile programs using the GNU C Library; the other
 654 directories describe interfaces to the kernel but are not required if
 655 not compiling programs using those interfaces.  You do not need to copy
 656 kernel headers if you did not specify an alternate kernel header source
 657 using ‘--with-headers’.
 658
 659    The Filesystem Hierarchy Standard for GNU/Linux systems expects some
 660 components of the GNU C Library installation to be in ‘/lib’ and some in
 661 ‘/usr/lib’.  This is handled automatically if you configure the GNU C
 662 Library with ‘--prefix=/usr’.  If you set some other prefix or allow it
 663 to default to ‘/usr/local’, then all the components are installed there.
 664
 665    As of release time, Linux version 6.1.5 is the newest stable version
 666 verified to work to build the GNU C Library.
 667
 668 Reporting Bugs
 669 ==============
 670
 671 There are probably bugs in the GNU C Library.  There are certainly
 672 errors and omissions in this manual.  If you report them, they will get
 673 fixed.  If you don’t, no one will ever know about them and they will
 674 remain unfixed for all eternity, if not longer.
 675
 676    It is a good idea to verify that the problem has not already been
 677 reported.  Bugs are documented in two places: The file ‘BUGS’ describes
 678 a number of well known bugs and the central GNU C Library bug tracking
 679 system has a WWW interface at <https://sourceware.org/bugzilla/>.  The
 680 WWW interface gives you access to open and closed reports.  A closed
 681 report normally includes a patch or a hint on solving the problem.
 682
 683    To report a bug, first you must find it.  With any luck, this will be
 684 the hard part.  Once you’ve found a bug, make sure it’s really a bug.  A
 685 good way to do this is to see if the GNU C Library behaves the same way
 686 some other C library does.  If so, probably you are wrong and the
 687 libraries are right (but not necessarily).  If not, one of the libraries
 688 is probably wrong.  It might not be the GNU C Library.  Many historical
 689 Unix C libraries permit things that we don’t, such as closing a file
 690 twice.
 691
 692    If you think you have found some way in which the GNU C Library does
 693 not conform to the ISO and POSIX standards (*note Standards and
 694 Portability::), that is definitely a bug.  Report it!
 695
 696    Once you’re sure you’ve found a bug, try to narrow it down to the
 697 smallest test case that reproduces the problem.  In the case of a C
 698 library, you really only need to narrow it down to one library function
 699 call, if possible.  This should not be too difficult.
 700
 701    The final step when you have a simple test case is to report the bug.
 702 Do this at <https://www.gnu.org/software/libc/bugs.html>.
 703
 704    If you are not sure how a function should behave, and this manual
 705 doesn’t tell you, that’s a bug in the manual.  Report that too!  If the
 706 function’s behavior disagrees with the manual, then either the library
 707 or the manual has a bug, so report the disagreement.  If you find any
 708 errors or omissions in this manual, please report them to the bug
 709 database.  If you refer to specific sections of the manual, please
 710 include the section names for easier identification.