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glibc/INSTALL
Andreas K. Hüttel 068b04eaed
INSTALL, install.texi: minor updates, regenerate 
Signed-off-by: Andreas K. Hüttel <dilfridge@gentoo.org>
2024-01-31 00:13:43 +01:00

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Installing the GNU C Library
****************************
Before you do anything else, you should read the FAQ at
<https://sourceware.org/glibc/wiki/FAQ>. It answers common questions
and describes problems you may experience with compilation and
installation.
You will need recent versions of several GNU tools: definitely GCC
and GNU Make, and possibly others. *Note Tools for Compilation::,
below.
Configuring and compiling the GNU C Library
===========================================
The GNU C Library cannot be compiled in the source directory. You must
build it in a separate build directory. For example, if you have
unpacked the GNU C Library sources in ‘/src/gnu/glibc-VERSION’, create a
directory ‘/src/gnu/glibc-build’ to put the object files in. This
allows removing the whole build directory in case an error occurs, which
is the safest way to get a fresh start and should always be done.
From your object directory, run the shell script ‘configure’ located
at the top level of the source tree. In the scenario above, you’d type
$ ../glibc-VERSION/configure ARGS...
Please note that even though you’re building in a separate build
directory, the compilation may need to create or modify files and
directories in the source directory.
‘configure’ takes many options, but the only one that is usually
mandatory is ‘--prefix’. This option tells ‘configure’ where you want
the GNU C Library installed. This defaults to ‘/usr/local’, but the
normal setting to install as the standard system library is
‘--prefix=/usr’ for GNU/Linux systems and ‘--prefix=’ (an empty prefix)
for GNU/Hurd systems.
It may also be useful to pass ‘CC=COMPILER’ and ‘CFLAGS=FLAGS’
arguments to ‘configure’. ‘CC’ selects the C compiler that will be
used, and ‘CFLAGS’ sets optimization options for the compiler. Any
compiler options required for all compilations, such as options
selecting an ABI or a processor for which to generate code, should be
included in ‘CC’. Options that may be overridden by the GNU C Library
build system for particular files, such as for optimization and
debugging, should go in ‘CFLAGS’. The default value of ‘CFLAGS’ is ‘-g
-O2’, and the GNU C Library cannot be compiled without optimization, so
if ‘CFLAGS’ is specified it must enable optimization. For example:
$ ../glibc-VERSION/configure CC="gcc -m32" CFLAGS="-O3"
The following list describes all of the available options for
‘configure’:
‘--prefix=DIRECTORY’
Install machine-independent data files in subdirectories of
‘DIRECTORY’. The default is to install in ‘/usr/local’.
‘--exec-prefix=DIRECTORY’
Install the library and other machine-dependent files in
subdirectories of ‘DIRECTORY’. The default is to the ‘--prefix’
directory if that option is specified, or ‘/usr/local’ otherwise.
‘--with-headers=DIRECTORY’
Look for kernel header files in DIRECTORY, not ‘/usr/include’. The
GNU C Library needs information from the kernel’s header files
describing the interface to the kernel. The GNU C Library will
normally look in ‘/usr/include’ for them, but if you specify this
option, it will look in DIRECTORY instead.
This option is primarily of use on a system where the headers in
‘/usr/include’ come from an older version of the GNU C Library.
Conflicts can occasionally happen in this case. You can also use
this option if you want to compile the GNU C Library with a newer
set of kernel headers than the ones found in ‘/usr/include’.
‘--enable-kernel=VERSION’
This option is currently only useful on GNU/Linux systems. The
VERSION parameter should have the form X.Y.Z and describes the
smallest version of the Linux kernel the generated library is
expected to support. The higher the VERSION number is, the less
compatibility code is added, and the faster the code gets.
‘--with-binutils=DIRECTORY’
Use the binutils (assembler and linker) in ‘DIRECTORY’, not the
ones the C compiler would default to. You can use this option if
the default binutils on your system cannot deal with all the
constructs in the GNU C Library. In that case, ‘configure’ will
detect the problem and suppress these constructs, so that the
library will still be usable, but functionality may be lost—for
example, you can’t build a shared libc with old binutils.
‘--with-nonshared-cflags=CFLAGS’
Use additional compiler flags CFLAGS to build the parts of the
library which are always statically linked into applications and
libraries even with shared linking (that is, the object files
contained in ‘lib*_nonshared.a’ libraries). The build process will
automatically use the appropriate flags, but this option can be
used to set additional flags required for building applications and
libraries, to match local policy. For example, if such a policy
requires that all code linked into applications must be built with
source fortification,
‘--with-nonshared-cflags=-Wp,-D_FORTIFY_SOURCE=2’ will make sure
that the objects in ‘libc_nonshared.a’ are compiled with this flag
(although this will not affect the generated code in this
particular case and potentially change debugging information and
metadata only).
‘--with-rtld-early-cflags=CFLAGS’
Use additional compiler flags CFLAGS to build the early startup
code of the dynamic linker. These flags can be used to enable
early dynamic linker diagnostics to run on CPUs which are not
compatible with the rest of the GNU C Library, for example, due to
compiler flags which target a later instruction set architecture
(ISA).
‘--with-timeoutfactor=NUM’
Specify an integer NUM to scale the timeout of test programs. This
factor can be changed at run time using ‘TIMEOUTFACTOR’ environment
variable.
‘--disable-shared’
Don’t build shared libraries even if it is possible. Not all
systems support shared libraries; you need ELF support and
(currently) the GNU linker.
‘--disable-default-pie’
Don’t build glibc programs and the testsuite as position
independent executables (PIE). By default, glibc programs and tests
are created as position independent executables on targets that
support it. If the toolchain and architecture support it, static
executables are built as static PIE and the resulting glibc can be
used with the GCC option, -static-pie, which is available with GCC
8 or above, to create static PIE.
‘--enable-cet’
‘--enable-cet=permissive’
Enable Intel Control-flow Enforcement Technology (CET) support.
When the GNU C Library is built with ‘--enable-cet’ or
‘--enable-cet=permissive’, the resulting library is protected with
indirect branch tracking (IBT) and shadow stack (SHSTK). When CET
is enabled, the GNU C Library is compatible with all existing
executables and shared libraries. This feature is currently
supported on x86_64 and x32 with GCC 8 and binutils 2.29 or later.
With ‘--enable-cet’, it is an error to dlopen a non CET enabled
shared library in CET enabled application. With
‘--enable-cet=permissive’, CET is disabled when dlopening a non CET
enabled shared library in CET enabled application.
NOTE: ‘--enable-cet’ is only supported on x86_64 and x32.
‘--enable-memory-tagging’
Enable memory tagging support if the architecture supports it.
When the GNU C Library is built with this option then the resulting
library will be able to control the use of tagged memory when
hardware support is present by use of the tunable
‘glibc.mem.tagging’. This includes the generation of tagged memory
when using the ‘malloc’ APIs.
At present only AArch64 platforms with MTE provide this
functionality, although the library will still operate (without
memory tagging) on older versions of the architecture.
The default is to disable support for memory tagging.
‘--disable-profile’
Don’t build libraries with profiling information. You may want to
use this option if you don’t plan to do profiling.
‘--enable-static-nss’
Compile static versions of the NSS (Name Service Switch) libraries.
This is not recommended because it defeats the purpose of NSS; a
program linked statically with the NSS libraries cannot be
dynamically reconfigured to use a different name database.
‘--enable-hardcoded-path-in-tests’
By default, dynamic tests are linked to run with the installed C
library. This option hardcodes the newly built C library path in
dynamic tests so that they can be invoked directly.
‘--disable-timezone-tools’
By default, timezone related utilities (‘zic’, ‘zdump’, and
‘tzselect’) are installed with the GNU C Library. If you are
building these independently (e.g. by using the ‘tzcode’ package),
then this option will allow disabling the install of these.
Note that you need to make sure the external tools are kept in sync
with the versions that the GNU C Library expects as the data
formats may change over time. Consult the ‘timezone’ subdirectory
for more details.
‘--enable-stack-protector’
‘--enable-stack-protector=strong’
‘--enable-stack-protector=all’
Compile the C library and all other parts of the glibc package
(including the threading and math libraries, NSS modules, and
transliteration modules) using the GCC ‘-fstack-protector’,
‘-fstack-protector-strong’ or ‘-fstack-protector-all’ options to
detect stack overruns. Only the dynamic linker and a small number
of routines called directly from assembler are excluded from this
protection.
‘--enable-bind-now’
Disable lazy binding for installed shared objects and programs.
This provides additional security hardening because it enables full
RELRO and a read-only global offset table (GOT), at the cost of
slightly increased program load times.
‘--enable-pt_chown’
The file ‘pt_chown’ is a helper binary for ‘grantpt’ (*note
Pseudo-Terminals: Allocation.) that is installed setuid root to fix
up pseudo-terminal ownership on GNU/Hurd. It is not required on
GNU/Linux, and the GNU C Library will not use the installed
‘pt_chown’ program when configured with ‘--enable-pt_chown’.
‘--disable-werror’
By default, the GNU C Library is built with ‘-Werror’. If you wish
to build without this option (for example, if building with a newer
version of GCC than this version of the GNU C Library was tested
with, so new warnings cause the build with ‘-Werror’ to fail), you
can configure with ‘--disable-werror’.
‘--disable-mathvec’
By default for x86_64, the GNU C Library is built with the vector
math library. Use this option to disable the vector math library.
‘--disable-scv’
Disable using ‘scv’ instruction for syscalls. All syscalls will
use ‘sc’ instead, even if the kernel supports ‘scv’. PowerPC only.
‘--build=BUILD-SYSTEM’
‘--host=HOST-SYSTEM’
These options are for cross-compiling. If you specify both options
and BUILD-SYSTEM is different from HOST-SYSTEM, ‘configure’ will
prepare to cross-compile the GNU C Library from BUILD-SYSTEM to be
used on HOST-SYSTEM. You’ll probably need the ‘--with-headers’
option too, and you may have to override CONFIGURE’s selection of
the compiler and/or binutils.
If you only specify ‘--host’, ‘configure’ will prepare for a native
compile but use what you specify instead of guessing what your
system is. This is most useful to change the CPU submodel. For
example, if ‘configure’ guesses your machine as ‘i686-pc-linux-gnu’
but you want to compile a library for 586es, give
‘--host=i586-pc-linux-gnu’ or just ‘--host=i586-linux’ and add the
appropriate compiler flags (‘-mcpu=i586’ will do the trick) to
‘CC’.
If you specify just ‘--build’, ‘configure’ will get confused.
‘--with-pkgversion=VERSION’
Specify a description, possibly including a build number or build
date, of the binaries being built, to be included in ‘--version’
output from programs installed with the GNU C Library. For
example, ‘--with-pkgversion='FooBar GNU/Linux glibc build 123'’.
The default value is ‘GNU libc’.
‘--with-bugurl=URL’
Specify the URL that users should visit if they wish to report a
bug, to be included in ‘--help’ output from programs installed with
the GNU C Library. The default value refers to the main
bug-reporting information for the GNU C Library.
‘--enable-fortify-source’
‘--enable-fortify-source=LEVEL’
Use -D_FORTIFY_SOURCE=‘LEVEL’ to control hardening in the GNU C
Library. If not provided, ‘LEVEL’ defaults to highest possible
value supported by the build compiler.
Default is to disable fortification.
To build the library and related programs, type ‘make’. This will
produce a lot of output, some of which may look like errors from ‘make’
but aren’t. Look for error messages from ‘make’ containing ‘***’.
Those indicate that something is seriously wrong.
The compilation process can take a long time, depending on the
configuration and the speed of your machine. Some complex modules may
take a very long time to compile, as much as several minutes on slower
machines. Do not panic if the compiler appears to hang.
If you want to run a parallel make, simply pass the ‘-j’ option with
an appropriate numeric parameter to ‘make’. You need a recent GNU
‘make’ version, though.
To build and run test programs which exercise some of the library
facilities, type ‘make check’. If it does not complete successfully, do
not use the built library, and report a bug after verifying that the
problem is not already known. *Note Reporting Bugs::, for instructions
on reporting bugs. Note that some of the tests assume they are not
being run by ‘root’. We recommend you compile and test the GNU C
Library as an unprivileged user.
Before reporting bugs make sure there is no problem with your system.
The tests (and later installation) use some pre-existing files of the
system such as ‘/etc/passwd’, ‘/etc/nsswitch.conf’ and others. These
files must all contain correct and sensible content.
Normally, ‘make check’ will run all the tests before reporting all
problems found and exiting with error status if any problems occurred.
You can specify ‘stop-on-test-failure=y’ when running ‘make check’ to
make the test run stop and exit with an error status immediately when a
failure occurs.
To format the ‘GNU C Library Reference Manual’ for printing, type
‘make dvi’. You need a working TeX installation to do this. The
distribution builds the on-line formatted version of the manual, as Info
files, as part of the build process. You can build them manually with
‘make info’.
The library has a number of special-purpose configuration parameters
which you can find in ‘Makeconfig’. These can be overwritten with the
file ‘configparms’. To change them, create a ‘configparms’ in your
build directory and add values as appropriate for your system. The file
is included and parsed by ‘make’ and has to follow the conventions for
makefiles.
It is easy to configure the GNU C Library for cross-compilation by
setting a few variables in ‘configparms’. Set ‘CC’ to the
cross-compiler for the target you configured the library for; it is
important to use this same ‘CC’ value when running ‘configure’, like
this: ‘configure TARGET CC=TARGET-gcc’. Set ‘BUILD_CC’ to the compiler
to use for programs run on the build system as part of compiling the
library. You may need to set ‘AR’ to cross-compiling versions of ‘ar’
if the native tools are not configured to work with object files for the
target you configured for. When cross-compiling the GNU C Library, it
may be tested using ‘make check
test-wrapper="SRCDIR/scripts/cross-test-ssh.sh HOSTNAME"’, where SRCDIR
is the absolute directory name for the main source directory and
HOSTNAME is the host name of a system that can run the newly built
binaries of the GNU C Library. The source and build directories must be
visible at the same locations on both the build system and HOSTNAME.
The ‘cross-test-ssh.sh’ script requires ‘flock’ from ‘util-linux’ to
work when GLIBC_TEST_ALLOW_TIME_SETTING environment variable is set.
It is also possible to execute tests, which require setting the date
on the target machine. Following use cases are supported:
• ‘GLIBC_TEST_ALLOW_TIME_SETTING’ is set in the environment in which
eligible tests are executed and have the privilege to run
‘clock_settime’. In this case, nothing prevents those tests from
running in parallel, so the caller shall assure that those tests
are serialized or provide a proper wrapper script for them.
• The ‘cross-test-ssh.sh’ script is used and one passes the
‘--allow-time-setting’ flag. In this case, both sets
‘GLIBC_TEST_ALLOW_TIME_SETTING’ and serialization of test execution
are assured automatically.
In general, when testing the GNU C Library, ‘test-wrapper’ may be set
to the name and arguments of any program to run newly built binaries.
This program must preserve the arguments to the binary being run, its
working directory and the standard input, output and error file
descriptors. If ‘TEST-WRAPPER env’ will not work to run a program with
environment variables set, then ‘test-wrapper-env’ must be set to a
program that runs a newly built program with environment variable
assignments in effect, those assignments being specified as ‘VAR=VALUE’
before the name of the program to be run. If multiple assignments to
the same variable are specified, the last assignment specified must take
precedence. Similarly, if ‘TEST-WRAPPER env -i’ will not work to run a
program with an environment completely empty of variables except those
directly assigned, then ‘test-wrapper-env-only’ must be set; its use has
the same syntax as ‘test-wrapper-env’, the only difference in its
semantics being starting with an empty set of environment variables
rather than the ambient set.
For AArch64 with SVE, when testing the GNU C Library, ‘test-wrapper’
may be set to "SRCDIR/sysdeps/unix/sysv/linux/aarch64/vltest.py
VECTOR-LENGTH" to change Vector Length.
Installing the C Library
========================
To install the library and its header files, and the Info files of the
manual, type ‘make install’. This will build things, if necessary,
before installing them; however, you should still compile everything
first. If you are installing the GNU C Library as your primary C
library, we recommend that you shut the system down to single-user mode
first, and reboot afterward. This minimizes the risk of breaking things
when the library changes out from underneath.
‘make install’ will do the entire job of upgrading from a previous
installation of the GNU C Library version 2.x. There may sometimes be
headers left behind from the previous installation, but those are
generally harmless. If you want to avoid leaving headers behind you can
do things in the following order.
You must first build the library (‘make’), optionally check it (‘make
check’), switch the include directories and then install (‘make
install’). The steps must be done in this order. Not moving the
directory before install will result in an unusable mixture of header
files from both libraries, but configuring, building, and checking the
library requires the ability to compile and run programs against the old
library. The new ‘/usr/include’, after switching the include
directories and before installing the library should contain the Linux
headers, but nothing else. If you do this, you will need to restore any
headers from libraries other than the GNU C Library yourself after
installing the library.
You can install the GNU C Library somewhere other than where you
configured it to go by setting the ‘DESTDIR’ GNU standard make variable
on the command line for ‘make install’. The value of this variable is
prepended to all the paths for installation. This is useful when
setting up a chroot environment or preparing a binary distribution. The
directory should be specified with an absolute file name. Installing
with the ‘prefix’ and ‘exec_prefix’ GNU standard make variables set is
not supported.
The GNU C Library includes a daemon called ‘nscd’, which you may or
may not want to run. ‘nscd’ caches name service lookups; it can
dramatically improve performance with NIS+, and may help with DNS as
well.
One auxiliary program, ‘/usr/libexec/pt_chown’, is installed setuid
‘root’ if the ‘--enable-pt_chown’ configuration option is used. This
program is invoked by the ‘grantpt’ function; it sets the permissions on
a pseudoterminal so it can be used by the calling process. If you are
using a Linux kernel with the ‘devpts’ filesystem enabled and mounted at
‘/dev/pts’, you don’t need this program.
After installation you should configure the timezone and install
locales for your system. The time zone configuration ensures that your
system time matches the time for your current timezone. The locales
ensure that the display of information on your system matches the
expectations of your language and geographic region.
The GNU C Library is able to use two kinds of localization
information sources, the first is a locale database named
‘locale-archive’ which is generally installed as
‘/usr/lib/locale/locale-archive’. The locale archive has the benefit of
taking up less space and being very fast to load, but only if you plan
to install sixty or more locales. If you plan to install one or two
locales you can instead install individual locales into their self-named
directories e.g. ‘/usr/lib/locale/en_US.utf8’. For example to install
the German locale using the character set for UTF-8 with name ‘de_DE’
into the locale archive issue the command ‘localedef -i de_DE -f UTF-8
de_DE’, and to install just the one locale issue the command ‘localedef
--no-archive -i de_DE -f UTF-8 de_DE’. To configure all locales that
are supported by the GNU C Library, you can issue from your build
directory the command ‘make localedata/install-locales’ to install all
locales into the locale archive or ‘make
localedata/install-locale-files’ to install all locales as files in the
default configured locale installation directory (derived from
‘--prefix’ or ‘--localedir’). To install into an alternative system
root use ‘DESTDIR’ e.g. ‘make localedata/install-locale-files
DESTDIR=/opt/glibc’, but note that this does not change the configured
prefix.
To configure the locally used timezone, set the ‘TZ’ environment
variable. The script ‘tzselect’ helps you to select the right value.
As an example, for Germany, ‘tzselect’ would tell you to use
‘TZ='Europe/Berlin'’. For a system wide installation (the given paths
are for an installation with ‘--prefix=/usr’), link the timezone file
which is in ‘/usr/share/zoneinfo’ to the file ‘/etc/localtime’. For
Germany, you might execute ‘ln -s /usr/share/zoneinfo/Europe/Berlin
/etc/localtime’.
Recommended Tools for Compilation
=================================
We recommend installing the following GNU tools before attempting to
build the GNU C Library:
• GNU ‘make’ 4.0 or newer
As of release time, GNU ‘make’ 4.4.1 is the newest verified to work
to build the GNU C Library.
• GCC 6.2 or newer
GCC 6.2 or higher is required. In general it is recommended to use
the newest version of the compiler that is known to work for
building the GNU C Library, as newer compilers usually produce
better code. As of release time, GCC 13.2 is the newest compiler
verified to work to build the GNU C Library.
For PowerPC 64-bits little-endian (powerpc64le), a GCC version with
support for ‘-mno-gnu-attribute’, ‘-mabi=ieeelongdouble’, and
‘-mabi=ibmlondouble’ is required. Likewise, the compiler must also
support passing ‘-mlong-double-128’ with the preceding options. As
of release, this implies GCC 7.4 and newer (excepting GCC 7.5.0,
see GCC PR94200). These additional features are required for
building the GNU C Library with support for IEEE long double.
For ARC architecture builds, GCC 8.3 or higher is needed.
For s390x architecture builds, GCC 7.1 or higher is needed (See gcc
Bug 98269).
For AArch64 architecture builds with mathvec enabled, GCC 10 or
higher is needed due to dependency on arm_sve.h.
For multi-arch support it is recommended to use a GCC which has
been built with support for GNU indirect functions. This ensures
that correct debugging information is generated for functions
selected by IFUNC resolvers. This support can either be enabled by
configuring GCC with ‘--enable-gnu-indirect-function’, or by
enabling it by default by setting ‘default_gnu_indirect_function’
variable for a particular architecture in the GCC source file
‘gcc/config.gcc’.
You can use whatever compiler you like to compile programs that use
the GNU C Library.
Check the FAQ for any special compiler issues on particular
platforms.
• GNU ‘binutils’ 2.25 or later
You must use GNU ‘binutils’ (as and ld) to build the GNU C Library.
No other assembler or linker has the necessary functionality at the
moment. As of release time, GNU ‘binutils’ 2.42 is the newest
verified to work to build the GNU C Library.
For PowerPC 64-bits little-endian (powerpc64le), ‘objcopy’ is
required to support ‘--update-section’. This option requires
binutils 2.26 or newer.
ARC architecture needs ‘binutils’ 2.32 or higher for TLS related
fixes.
• GNU ‘texinfo’ 4.7 or later
To correctly translate and install the Texinfo documentation you
need this version of the ‘texinfo’ package. Earlier versions do
not understand all the tags used in the document, and the
installation mechanism for the info files is not present or works
differently. As of release time, ‘texinfo’ 7.0.3 is the newest
verified to work to build the GNU C Library.
• GNU ‘awk’ 3.1.2, or higher
‘awk’ is used in several places to generate files. Some ‘gawk’
extensions are used, including the ‘asorti’ function, which was
introduced in version 3.1.2 of ‘gawk’. As of release time, ‘gawk’
version 5.2.2 is the newest verified to work to build the GNU C
Library.
• GNU ‘bison’ 2.7 or later
‘bison’ is used to generate the ‘yacc’ parser code in the ‘intl’
subdirectory. As of release time, ‘bison’ version 3.8.2 is the
newest verified to work to build the GNU C Library.
• Perl 5
Perl is not required, but if present it is used in some tests and
the ‘mtrace’ program, to build the GNU C Library manual. As of
release time ‘perl’ version 5.38.2 is the newest verified to work
to build the GNU C Library.
• GNU ‘sed’ 3.02 or newer
‘Sed’ is used in several places to generate files. Most scripts
work with any version of ‘sed’. As of release time, ‘sed’ version
4.9 is the newest verified to work to build the GNU C Library.
• Python 3.4 or later
Python is required to build the GNU C Library. As of release time,
Python 3.11 is the newest verified to work for building and testing
the GNU C Library.
• PExpect 4.0
The pretty printer tests drive GDB through test programs and
compare its output to the printers’. PExpect is used to capture
the output of GDB, and should be compatible with the Python version
in your system. As of release time PExpect 4.8.0 is the newest
verified to work to test the pretty printers.
• The Python ‘abnf’ module.
This module is optional and used to verify some ABNF grammars in
the manual. Version 2.2.0 has been confirmed to work as expected.
A missing ‘abnf’ module does not reduce the test coverage of the
library itself.
• GDB 7.8 or later with support for Python 2.7/3.4 or later
GDB itself needs to be configured with Python support in order to
use the pretty printers. Notice that your system having Python
available doesn’t imply that GDB supports it, nor that your
system’s Python and GDB’s have the same version. As of release
time GNU ‘debugger’ 13.2 is the newest verified to work to test the
pretty printers.
Unless Python, PExpect and GDB with Python support are present, the
printer tests will report themselves as ‘UNSUPPORTED’. Notice that
some of the printer tests require the GNU C Library to be compiled
with debugging symbols.
If you change any of the ‘configure.ac’ files you will also need
• GNU ‘autoconf’ 2.71 (exactly)
and if you change any of the message translation files you will need
• GNU ‘gettext’ 0.10.36 or later
As of release time, GNU ‘gettext’ version 0.21.1 is the newest
version verified to work to build the GNU C Library.
You may also need these packages if you upgrade your source tree using
patches, although we try to avoid this.
Specific advice for GNU/Linux systems
=====================================
If you are installing the GNU C Library on GNU/Linux systems, you need
to have the header files from a 3.2 or newer kernel around for
reference. These headers must be installed using ‘make
headers_install’; the headers present in the kernel source directory are
not suitable for direct use by the GNU C Library. You do not need to
use that kernel, just have its headers installed where the GNU C Library
can access them, referred to here as INSTALL-DIRECTORY. The easiest way
to do this is to unpack it in a directory such as
‘/usr/src/linux-VERSION’. In that directory, run ‘make headers_install
INSTALL_HDR_PATH=INSTALL-DIRECTORY’. Finally, configure the GNU C
Library with the option ‘--with-headers=INSTALL-DIRECTORY/include’. Use
the most recent kernel you can get your hands on. (If you are
cross-compiling the GNU C Library, you need to specify
‘ARCH=ARCHITECTURE’ in the ‘make headers_install’ command, where
ARCHITECTURE is the architecture name used by the Linux kernel, such as
‘x86’ or ‘powerpc’.)
After installing the GNU C Library, you may need to remove or rename
directories such as ‘/usr/include/linux’ and ‘/usr/include/asm’, and
replace them with copies of directories such as ‘linux’ and ‘asm’ from
‘INSTALL-DIRECTORY/include’. All directories present in
‘INSTALL-DIRECTORY/include’ should be copied, except that the GNU C
Library provides its own version of ‘/usr/include/scsi’; the files
provided by the kernel should be copied without replacing those provided
by the GNU C Library. The ‘linux’, ‘asm’ and ‘asm-generic’ directories
are required to compile programs using the GNU C Library; the other
directories describe interfaces to the kernel but are not required if
not compiling programs using those interfaces. You do not need to copy
kernel headers if you did not specify an alternate kernel header source
using ‘--with-headers’.
The Filesystem Hierarchy Standard for GNU/Linux systems expects some
components of the GNU C Library installation to be in ‘/lib’ and some in
‘/usr/lib’. This is handled automatically if you configure the GNU C
Library with ‘--prefix=/usr’. If you set some other prefix or allow it
to default to ‘/usr/local’, then all the components are installed there.
As of release time, Linux version 6.1.5 is the newest stable version
verified to work to build the GNU C Library.
Reporting Bugs
==============
There are probably bugs in the GNU C Library. There are certainly
errors and omissions in this manual. If you report them, they will get
fixed. If you don’t, no one will ever know about them and they will
remain unfixed for all eternity, if not longer.
It is a good idea to verify that the problem has not already been
reported. Bugs are documented in two places: The file ‘BUGS’ describes
a number of well known bugs and the central GNU C Library bug tracking
system has a WWW interface at <https://sourceware.org/bugzilla/>. The
WWW interface gives you access to open and closed reports. A closed
report normally includes a patch or a hint on solving the problem.
To report a bug, first you must find it. With any luck, this will be
the hard part. Once you’ve found a bug, make sure it’s really a bug. A
good way to do this is to see if the GNU C Library behaves the same way
some other C library does. If so, probably you are wrong and the
libraries are right (but not necessarily). If not, one of the libraries
is probably wrong. It might not be the GNU C Library. Many historical
Unix C libraries permit things that we don’t, such as closing a file
twice.
If you think you have found some way in which the GNU C Library does
not conform to the ISO and POSIX standards (*note Standards and
Portability::), that is definitely a bug. Report it!
Once you’re sure you’ve found a bug, try to narrow it down to the
smallest test case that reproduces the problem. In the case of a C
library, you really only need to narrow it down to one library function
call, if possible. This should not be too difficult.
The final step when you have a simple test case is to report the bug.
Do this at <https://www.gnu.org/software/libc/bugs.html>.
If you are not sure how a function should behave, and this manual
doesn’t tell you, that’s a bug in the manual. Report that too! If the
function’s behavior disagrees with the manual, then either the library
or the manual has a bug, so report the disagreement. If you find any
errors or omissions in this manual, please report them to the bug
database. If you refer to specific sections of the manual, please
include the section names for easier identification.
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