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 set the CC and CFLAGS variables in the
  40 environment when running 'configure'.  CC selects the C compiler that
  41 will be used, and CFLAGS sets optimization options for the compiler.
  42
  43    The following list describes all of the available options for
  44 'configure':
  45
  46 '--prefix=DIRECTORY'
  47      Install machine-independent data files in subdirectories of
  48      'DIRECTORY'.  The default is to install in '/usr/local'.
  49
  50 '--exec-prefix=DIRECTORY'
  51      Install the library and other machine-dependent files in
  52      subdirectories of 'DIRECTORY'.  The default is to the '--prefix'
  53      directory if that option is specified, or '/usr/local' otherwise.
  54
  55 '--with-headers=DIRECTORY'
  56      Look for kernel header files in DIRECTORY, not '/usr/include'.  The
  57      GNU C Library needs information from the kernel's header files
  58      describing the interface to the kernel.  The GNU C Library will
  59      normally look in '/usr/include' for them, but if you specify this
  60      option, it will look in DIRECTORY instead.
  61
  62      This option is primarily of use on a system where the headers in
  63      '/usr/include' come from an older version of the GNU C Library.
  64      Conflicts can occasionally happen in this case.  You can also use
  65      this option if you want to compile the GNU C Library with a newer
  66      set of kernel headers than the ones found in '/usr/include'.
  67
  68 '--enable-kernel=VERSION'
  69      This option is currently only useful on GNU/Linux systems.  The
  70      VERSION parameter should have the form X.Y.Z and describes the
  71      smallest version of the Linux kernel the generated library is
  72      expected to support.  The higher the VERSION number is, the less
  73      compatibility code is added, and the faster the code gets.
  74
  75 '--with-binutils=DIRECTORY'
  76      Use the binutils (assembler and linker) in 'DIRECTORY', not the
  77      ones the C compiler would default to.  You can use this option if
  78      the default binutils on your system cannot deal with all the
  79      constructs in the GNU C Library.  In that case, 'configure' will
  80      detect the problem and suppress these constructs, so that the
  81      library will still be usable, but functionality may be lost--for
  82      example, you can't build a shared libc with old binutils.
  83
  84 '--without-fp'
  85      Use this option if your computer lacks hardware floating-point
  86      support and your operating system does not emulate an FPU.
  87
  88 '--disable-shared'
  89      Don't build shared libraries even if it is possible.  Not all
  90      systems support shared libraries; you need ELF support and
  91      (currently) the GNU linker.
  92
  93 '--disable-profile'
  94      Don't build libraries with profiling information.  You may want to
  95      use this option if you don't plan to do profiling.
  96
  97 '--enable-static-nss'
  98      Compile static versions of the NSS (Name Service Switch) libraries.
  99      This is not recommended because it defeats the purpose of NSS; a
 100      program linked statically with the NSS libraries cannot be
 101      dynamically reconfigured to use a different name database.
 102
 103 '--enable-hardcoded-path-in-tests'
 104      By default, dynamic tests are linked to run with the installed C
 105      library.  This option hardcodes the newly built C library path in
 106      dynamic tests so that they can be invoked directly.
 107
 108 '--disable-timezone-tools'
 109      By default, timezone related utilities ('zic', 'zdump', and
 110      'tzselect') are installed with the GNU C Library.  If you are
 111      building these independently (e.g.  by using the 'tzcode' package),
 112      then this option will allow disabling the install of these.
 113
 114      Note that you need to make sure the external tools are kept in sync
 115      with the versions that the GNU C Library expects as the data
 116      formats may change over time.  Consult the 'timezone' subdirectory
 117      for more details.
 118
 119 '--enable-stack-protector'
 120 '--enable-stack-protector=strong'
 121 '--enable-stack-protector=all'
 122      Compile the C library and all other parts of the glibc package
 123      (including the threading and math libraries, NSS modules, and
 124      transliteration modules) using the GCC '-fstack-protector',
 125      '-fstack-protector-strong' or '-fstack-protector-all' options to
 126      detect stack overruns.  Only the dynamic linker and a small number
 127      of routines called directly from assembler are excluded from this
 128      protection.
 129
 130 '--enable-bind-now'
 131      Disable lazy binding for installed shared objects.  This provides
 132      additional security hardening because it enables full RELRO and a
 133      read-only global offset table (GOT), at the cost of slightly
 134      increased program load times.
 135
 136 '--enable-pt_chown'
 137      The file 'pt_chown' is a helper binary for 'grantpt' (*note
 138      Pseudo-Terminals: Allocation.) that is installed setuid root to fix
 139      up pseudo-terminal ownership.  It is not built by default because
 140      systems using the Linux kernel are commonly built with the 'devpts'
 141      filesystem enabled and mounted at '/dev/pts', which manages
 142      pseudo-terminal ownership automatically.  By using
 143      '--enable-pt_chown', you may build 'pt_chown' and install it setuid
 144      and owned by 'root'.  The use of 'pt_chown' introduces additional
 145      security risks to the system and you should enable it only if you
 146      understand and accept those risks.
 147
 148 '--disable-werror'
 149      By default, the GNU C Library is built with '-Werror'.  If you wish
 150      to build without this option (for example, if building with a newer
 151      version of GCC than this version of the GNU C Library was tested
 152      with, so new warnings cause the build with '-Werror' to fail), you
 153      can configure with '--disable-werror'.
 154
 155 '--disable-mathvec'
 156      By default for x86_64, the GNU C Library is built with the vector
 157      math library.  Use this option to disable the vector math library.
 158
 159 '--enable-tunables'
 160      Tunables support allows additional library parameters to be
 161      customized at runtime.  This feature is enabled by default.  This
 162      option can take the following values:
 163
 164      'yes'
 165           This is the default if no option is passed to configure.  This
 166           enables tunables and selects the default frontend (currently
 167           'valstring').
 168
 169      'no'
 170           This option disables tunables.
 171
 172      'valstring'
 173           This enables tunables and selects the 'valstring' frontend for
 174           tunables.  This frontend allows users to specify tunables as a
 175           colon-separated list in a single environment variable
 176           'GLIBC_TUNABLES'.
 177
 178 '--enable-obsolete-nsl'
 179      By default, libnsl is only built as shared library for backward
 180      compatibility and the NSS modules libnss_compat, libnss_nis and
 181      libnss_nisplus are not built at all.  Use this option to enable
 182      libnsl with all depending NSS modules and header files.
 183
 184 '--disable-experimental-malloc'
 185      By default, a per-thread cache is enabled in 'malloc'.  While this
 186      cache can be disabled on a per-application basis using tunables
 187      (set glibc.malloc.tcache_count to zero), this option can be used to
 188      remove it from the build completely.
 189
 190 '--build=BUILD-SYSTEM'
 191 '--host=HOST-SYSTEM'
 192      These options are for cross-compiling.  If you specify both options
 193      and BUILD-SYSTEM is different from HOST-SYSTEM, 'configure' will
 194      prepare to cross-compile the GNU C Library from BUILD-SYSTEM to be
 195      used on HOST-SYSTEM.  You'll probably need the '--with-headers'
 196      option too, and you may have to override CONFIGURE's selection of
 197      the compiler and/or binutils.
 198
 199      If you only specify '--host', 'configure' will prepare for a native
 200      compile but use what you specify instead of guessing what your
 201      system is.  This is most useful to change the CPU submodel.  For
 202      example, if 'configure' guesses your machine as 'i686-pc-linux-gnu'
 203      but you want to compile a library for 586es, give
 204      '--host=i586-pc-linux-gnu' or just '--host=i586-linux' and add the
 205      appropriate compiler flags ('-mcpu=i586' will do the trick) to
 206      CFLAGS.
 207
 208      If you specify just '--build', 'configure' will get confused.
 209
 210 '--with-pkgversion=VERSION'
 211      Specify a description, possibly including a build number or build
 212      date, of the binaries being built, to be included in '--version'
 213      output from programs installed with the GNU C Library.  For
 214      example, '--with-pkgversion='FooBar GNU/Linux glibc build 123''.
 215      The default value is 'GNU libc'.
 216
 217 '--with-bugurl=URL'
 218      Specify the URL that users should visit if they wish to report a
 219      bug, to be included in '--help' output from programs installed with
 220      the GNU C Library.  The default value refers to the main
 221      bug-reporting information for the GNU C Library.
 222
 223    To build the library and related programs, type 'make'.  This will
 224 produce a lot of output, some of which may look like errors from 'make'
 225 but aren't.  Look for error messages from 'make' containing '***'.
 226 Those indicate that something is seriously wrong.
 227
 228    The compilation process can take a long time, depending on the
 229 configuration and the speed of your machine.  Some complex modules may
 230 take a very long time to compile, as much as several minutes on slower
 231 machines.  Do not panic if the compiler appears to hang.
 232
 233    If you want to run a parallel make, simply pass the '-j' option with
 234 an appropriate numeric parameter to 'make'.  You need a recent GNU
 235 'make' version, though.
 236
 237    To build and run test programs which exercise some of the library
 238 facilities, type 'make check'.  If it does not complete successfully, do
 239 not use the built library, and report a bug after verifying that the
 240 problem is not already known.  *Note Reporting Bugs::, for instructions
 241 on reporting bugs.  Note that some of the tests assume they are not
 242 being run by 'root'.  We recommend you compile and test the GNU C
 243 Library as an unprivileged user.
 244
 245    Before reporting bugs make sure there is no problem with your system.
 246 The tests (and later installation) use some pre-existing files of the
 247 system such as '/etc/passwd', '/etc/nsswitch.conf' and others.  These
 248 files must all contain correct and sensible content.
 249
 250    Normally, 'make check' will run all the tests before reporting all
 251 problems found and exiting with error status if any problems occurred.
 252 You can specify 'stop-on-test-failure=y' when running 'make check' to
 253 make the test run stop and exit with an error status immediately when a
 254 failure occurs.
 255
 256    The GNU C Library pretty printers come with their own set of scripts
 257 for testing, which run together with the rest of the testsuite through
 258 'make check'.  These scripts require the following tools to run
 259 successfully:
 260
 261    * Python 2.7.6/3.4.3 or later
 262
 263      Python is required for running the printers' test scripts.
 264
 265    * PExpect 4.0
 266
 267      The printer tests drive GDB through test programs and compare its
 268      output to the printers'.  PExpect is used to capture the output of
 269      GDB, and should be compatible with the Python version in your
 270      system.
 271
 272    * GDB 7.8 or later with support for Python 2.7.6/3.4.3 or later
 273
 274      GDB itself needs to be configured with Python support in order to
 275      use the pretty printers.  Notice that your system having Python
 276      available doesn't imply that GDB supports it, nor that your
 277      system's Python and GDB's have the same version.
 278
 279 If these tools are absent, the printer tests will report themselves as
 280 'UNSUPPORTED'.  Notice that some of the printer tests require the GNU C
 281 Library to be compiled with debugging symbols.
 282
 283    To format the 'GNU C Library Reference Manual' for printing, type
 284 'make dvi'.  You need a working TeX installation to do this.  The
 285 distribution builds the on-line formatted version of the manual, as Info
 286 files, as part of the build process.  You can build them manually with
 287 'make info'.
 288
 289    The library has a number of special-purpose configuration parameters
 290 which you can find in 'Makeconfig'.  These can be overwritten with the
 291 file 'configparms'.  To change them, create a 'configparms' in your
 292 build directory and add values as appropriate for your system.  The file
 293 is included and parsed by 'make' and has to follow the conventions for
 294 makefiles.
 295
 296    It is easy to configure the GNU C Library for cross-compilation by
 297 setting a few variables in 'configparms'.  Set 'CC' to the
 298 cross-compiler for the target you configured the library for; it is
 299 important to use this same 'CC' value when running 'configure', like
 300 this: 'CC=TARGET-gcc configure TARGET'.  Set 'BUILD_CC' to the compiler
 301 to use for programs run on the build system as part of compiling the
 302 library.  You may need to set 'AR' to cross-compiling versions of 'ar'
 303 if the native tools are not configured to work with object files for the
 304 target you configured for.  When cross-compiling the GNU C Library, it
 305 may be tested using 'make check
 306 test-wrapper="SRCDIR/scripts/cross-test-ssh.sh HOSTNAME"', where SRCDIR
 307 is the absolute directory name for the main source directory and
 308 HOSTNAME is the host name of a system that can run the newly built
 309 binaries of the GNU C Library.  The source and build directories must be
 310 visible at the same locations on both the build system and HOSTNAME.
 311
 312    In general, when testing the GNU C Library, 'test-wrapper' may be set
 313 to the name and arguments of any program to run newly built binaries.
 314 This program must preserve the arguments to the binary being run, its
 315 working directory and the standard input, output and error file
 316 descriptors.  If 'TEST-WRAPPER env' will not work to run a program with
 317 environment variables set, then 'test-wrapper-env' must be set to a
 318 program that runs a newly built program with environment variable
 319 assignments in effect, those assignments being specified as 'VAR=VALUE'
 320 before the name of the program to be run.  If multiple assignments to
 321 the same variable are specified, the last assignment specified must take
 322 precedence.  Similarly, if 'TEST-WRAPPER env -i' will not work to run a
 323 program with an environment completely empty of variables except those
 324 directly assigned, then 'test-wrapper-env-only' must be set; its use has
 325 the same syntax as 'test-wrapper-env', the only difference in its
 326 semantics being starting with an empty set of environment variables
 327 rather than the ambient set.
 328
 329 Installing the C Library
 330 ========================
 331
 332 To install the library and its header files, and the Info files of the
 333 manual, type 'make install'.  This will build things, if necessary,
 334 before installing them; however, you should still compile everything
 335 first.  If you are installing the GNU C Library as your primary C
 336 library, we recommend that you shut the system down to single-user mode
 337 first, and reboot afterward.  This minimizes the risk of breaking things
 338 when the library changes out from underneath.
 339
 340    'make install' will do the entire job of upgrading from a previous
 341 installation of the GNU C Library version 2.x.  There may sometimes be
 342 headers left behind from the previous installation, but those are
 343 generally harmless.  If you want to avoid leaving headers behind you can
 344 do things in the following order.
 345
 346    You must first build the library ('make'), optionally check it ('make
 347 check'), switch the include directories and then install ('make
 348 install').  The steps must be done in this order.  Not moving the
 349 directory before install will result in an unusable mixture of header
 350 files from both libraries, but configuring, building, and checking the
 351 library requires the ability to compile and run programs against the old
 352 library.  The new '/usr/include', after switching the include
 353 directories and before installing the library should contain the Linux
 354 headers, but nothing else.  If you do this, you will need to restore any
 355 headers from libraries other than the GNU C Library yourself after
 356 installing the library.
 357
 358    You can install the GNU C Library somewhere other than where you
 359 configured it to go by setting the 'DESTDIR' GNU standard make variable
 360 on the command line for 'make install'.  The value of this variable is
 361 prepended to all the paths for installation.  This is useful when
 362 setting up a chroot environment or preparing a binary distribution.  The
 363 directory should be specified with an absolute file name.  Installing
 364 with the 'prefix' and 'exec_prefix' GNU standard make variables set is
 365 not supported.
 366
 367    The GNU C Library includes a daemon called 'nscd', which you may or
 368 may not want to run.  'nscd' caches name service lookups; it can
 369 dramatically improve performance with NIS+, and may help with DNS as
 370 well.
 371
 372    One auxiliary program, '/usr/libexec/pt_chown', is installed setuid
 373 'root' if the '--enable-pt_chown' configuration option is used.  This
 374 program is invoked by the 'grantpt' function; it sets the permissions on
 375 a pseudoterminal so it can be used by the calling process.  If you are
 376 using a Linux kernel with the 'devpts' filesystem enabled and mounted at
 377 '/dev/pts', you don't need this program.
 378
 379    After installation you might want to configure the timezone and
 380 locale installation of your system.  The GNU C Library comes with a
 381 locale database which gets configured with 'localedef'.  For example, to
 382 set up a German locale with name 'de_DE', simply issue the command
 383 'localedef -i de_DE -f ISO-8859-1 de_DE'.  To configure all locales that
 384 are supported by the GNU C Library, you can issue from your build
 385 directory the command 'make localedata/install-locales'.
 386
 387    To configure the locally used timezone, set the 'TZ' environment
 388 variable.  The script 'tzselect' helps you to select the right value.
 389 As an example, for Germany, 'tzselect' would tell you to use
 390 'TZ='Europe/Berlin''.  For a system wide installation (the given paths
 391 are for an installation with '--prefix=/usr'), link the timezone file
 392 which is in '/usr/share/zoneinfo' to the file '/etc/localtime'.  For
 393 Germany, you might execute 'ln -s /usr/share/zoneinfo/Europe/Berlin
 394 /etc/localtime'.
 395
 396 Recommended Tools for Compilation
 397 =================================
 398
 399 We recommend installing the following GNU tools before attempting to
 400 build the GNU C Library:
 401
 402    * GNU 'make' 3.79 or newer
 403
 404      You need the latest version of GNU 'make'.  Modifying the GNU C
 405      Library to work with other 'make' programs would be so difficult
 406      that we recommend you port GNU 'make' instead.  *Really.*  We
 407      recommend GNU 'make' version 3.79.  All earlier versions have
 408      severe bugs or lack features.
 409
 410    * GCC 4.9 or newer
 411
 412      GCC 4.9 or higher is required.  In general it is recommended to use
 413      the newest version of the compiler that is known to work for
 414      building the GNU C Library, as newer compilers usually produce
 415      better code.  As of release time, GCC 7.1 is the newest compiler
 416      verified to work to build the GNU C Library.
 417
 418      For PowerPC 64-bits little-endian (powerpc64le), GCC 6.2 or higher
 419      is required.  This compiler version is the first to provide the
 420      features required for building the GNU C Library with support for
 421      '_Float128'.
 422
 423      For multi-arch support it is recommended to use a GCC which has
 424      been built with support for GNU indirect functions.  This ensures
 425      that correct debugging information is generated for functions
 426      selected by IFUNC resolvers.  This support can either be enabled by
 427      configuring GCC with '--enable-gnu-indirect-function', or by
 428      enabling it by default by setting 'default_gnu_indirect_function'
 429      variable for a particular architecture in the GCC source file
 430      'gcc/config.gcc'.
 431
 432      You can use whatever compiler you like to compile programs that use
 433      the GNU C Library.
 434
 435      Check the FAQ for any special compiler issues on particular
 436      platforms.
 437
 438    * GNU 'binutils' 2.25 or later
 439
 440      You must use GNU 'binutils' (as and ld) to build the GNU C Library.
 441      No other assembler or linker has the necessary functionality at the
 442      moment.  As of release time, GNU 'binutils' 2.27 is the newest
 443      verified to work to build the GNU C Library.
 444
 445    * GNU 'texinfo' 4.7 or later
 446
 447      To correctly translate and install the Texinfo documentation you
 448      need this version of the 'texinfo' package.  Earlier versions do
 449      not understand all the tags used in the document, and the
 450      installation mechanism for the info files is not present or works
 451      differently.  As of release time, 'texinfo' 6.0 is the newest
 452      verified to work to build the GNU C Library.
 453
 454    * GNU 'awk' 3.1.2, or higher
 455
 456      'awk' is used in several places to generate files.  Some 'gawk'
 457      extensions are used, including the 'asorti' function, which was
 458      introduced in version 3.1.2 of 'gawk'.  As of release time, 'gawk'
 459      version 4.1.3 is the newest verified to work to build the GNU C
 460      Library.
 461
 462    * GNU 'bison' 2.7 or later
 463
 464      'bison' is used to generate the 'yacc' parser code in the 'intl'
 465      subdirectory.
 466
 467    * Perl 5
 468
 469      Perl is not required, but it is used if present to test the
 470      installation.  We may decide to use it elsewhere in the future.
 471
 472    * GNU 'sed' 3.02 or newer
 473
 474      'Sed' is used in several places to generate files.  Most scripts
 475      work with any version of 'sed'.  As of release time, 'sed' version
 476      4.2.2 is the newest verified to work to build the GNU C Library.
 477
 478 If you change any of the 'configure.ac' files you will also need
 479
 480    * GNU 'autoconf' 2.69 (exactly)
 481
 482 and if you change any of the message translation files you will need
 483
 484    * GNU 'gettext' 0.10.36 or later
 485
 486 You may also need these packages if you upgrade your source tree using
 487 patches, although we try to avoid this.
 488
 489 Specific advice for GNU/Linux systems
 490 =====================================
 491
 492 If you are installing the GNU C Library on GNU/Linux systems, you need
 493 to have the header files from a 3.2 or newer kernel around for
 494 reference.  (For the ia64 architecture, you need version 3.2.18 or newer
 495 because this is the first version with support for the 'accept4' system
 496 call.)  These headers must be installed using 'make headers_install';
 497 the headers present in the kernel source directory are not suitable for
 498 direct use by the GNU C Library.  You do not need to use that kernel,
 499 just have its headers installed where the GNU C Library can access them,
 500 referred to here as INSTALL-DIRECTORY.  The easiest way to do this is to
 501 unpack it in a directory such as '/usr/src/linux-VERSION'.  In that
 502 directory, run 'make headers_install
 503 INSTALL_HDR_PATH=INSTALL-DIRECTORY'.  Finally, configure the GNU C
 504 Library with the option '--with-headers=INSTALL-DIRECTORY/include'.  Use
 505 the most recent kernel you can get your hands on.  (If you are
 506 cross-compiling the GNU C Library, you need to specify
 507 'ARCH=ARCHITECTURE' in the 'make headers_install' command, where
 508 ARCHITECTURE is the architecture name used by the Linux kernel, such as
 509 'x86' or 'powerpc'.)
 510
 511    After installing the GNU C Library, you may need to remove or rename
 512 directories such as '/usr/include/linux' and '/usr/include/asm', and
 513 replace them with copies of directories such as 'linux' and 'asm' from
 514 'INSTALL-DIRECTORY/include'.  All directories present in
 515 'INSTALL-DIRECTORY/include' should be copied, except that the GNU C
 516 Library provides its own version of '/usr/include/scsi'; the files
 517 provided by the kernel should be copied without replacing those provided
 518 by the GNU C Library.  The 'linux', 'asm' and 'asm-generic' directories
 519 are required to compile programs using the GNU C Library; the other
 520 directories describe interfaces to the kernel but are not required if
 521 not compiling programs using those interfaces.  You do not need to copy
 522 kernel headers if you did not specify an alternate kernel header source
 523 using '--with-headers'.
 524
 525    The Filesystem Hierarchy Standard for GNU/Linux systems expects some
 526 components of the GNU C Library installation to be in '/lib' and some in
 527 '/usr/lib'.  This is handled automatically if you configure the GNU C
 528 Library with '--prefix=/usr'.  If you set some other prefix or allow it
 529 to default to '/usr/local', then all the components are installed there.
 530
 531 Reporting Bugs
 532 ==============
 533
 534 There are probably bugs in the GNU C Library.  There are certainly
 535 errors and omissions in this manual.  If you report them, they will get
 536 fixed.  If you don't, no one will ever know about them and they will
 537 remain unfixed for all eternity, if not longer.
 538
 539    It is a good idea to verify that the problem has not already been
 540 reported.  Bugs are documented in two places: The file 'BUGS' describes
 541 a number of well known bugs and the central GNU C Library bug tracking
 542 system has a WWW interface at <https://sourceware.org/bugzilla/>.  The
 543 WWW interface gives you access to open and closed reports.  A closed
 544 report normally includes a patch or a hint on solving the problem.
 545
 546    To report a bug, first you must find it.  With any luck, this will be
 547 the hard part.  Once you've found a bug, make sure it's really a bug.  A
 548 good way to do this is to see if the GNU C Library behaves the same way
 549 some other C library does.  If so, probably you are wrong and the
 550 libraries are right (but not necessarily).  If not, one of the libraries
 551 is probably wrong.  It might not be the GNU C Library.  Many historical
 552 Unix C libraries permit things that we don't, such as closing a file
 553 twice.
 554
 555    If you think you have found some way in which the GNU C Library does
 556 not conform to the ISO and POSIX standards (*note Standards and
 557 Portability::), that is definitely a bug.  Report it!
 558
 559    Once you're sure you've found a bug, try to narrow it down to the
 560 smallest test case that reproduces the problem.  In the case of a C
 561 library, you really only need to narrow it down to one library function
 562 call, if possible.  This should not be too difficult.
 563
 564    The final step when you have a simple test case is to report the bug.
 565 Do this at <http://www.gnu.org/software/libc/bugs.html>.
 566
 567    If you are not sure how a function should behave, and this manual
 568 doesn't tell you, that's a bug in the manual.  Report that too!  If the
 569 function's behavior disagrees with the manual, then either the library
 570 or the manual has a bug, so report the disagreement.  If you find any
 571 errors or omissions in this manual, please report them to the bug
 572 database.  If you refer to specific sections of the manual, please
 573 include the section names for easier identification.