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