     [file macros.texi not included]
     [file pkgvers.texi not included]

Installing theglibc
*******************

Before you do anything else, you should read the FAQ at http://sourceware.org/glibc/wiki/FAQ.  It answers common questions and describes problems you may experience with compilation and installation.

Features can be added to theglibc via add-on bundles.  These are separate tar files, which you unpack into the top level of the source tree.  Then you give configure the --enable-add-ons option to activate them, and they will be compiled into the library.

You will need recent versions of several GNU tools: definitely GCC and GNU Make, and possibly others.  See Tools for Compilation, below.

Configuring and compiling theglibc
==================================

Theglibc cannot be compiled in the source directory.  You must build it in a separate build directory.  For example, if you have unpacked the glibcadj 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 theglibc installed.  This defaults to /usr/local, but the normal setting to install as the standard system library is --prefix=/usr for gnulinuxsystems and --prefix= (an empty prefix) for gnuhurdsystems.

It may also be useful to set the CC and CFLAGS variables in the environment when running configure.  CC selects the C compiler that will be used, and CFLAGS sets optimization options for the compiler.

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.  Theglibc needs information from the kernel's header files describing the interface to the kernel.  Theglibc 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 theglibc.  Conflicts can occasionally happen in this case.  You can also use this option if you want to compile theglibc with a newer set of kernel headers than the ones found in /usr/include.

--enable-add-ons[=LIST]
     Specify add-on packages to include in the build.  If this option is specified with no list, it enables all the add-on packages it finds in the main source directory; this is the default behavior.  You may specify an explicit list of add-ons to use in LIST, separated by spaces or commas (if you use spaces, remember to quote them from the shell).  Each add-on in LIST can be an absolute directory name or can be a directory name relative to the main source directory, or relative to the build directory (that is, the current working directory). For example, --enable-add-ons=nptl,../glibc-libidn-VERSION.

--enable-kernel=VERSION
     This option is currently only useful on gnulinuxsystems.  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 theglibc.  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.

--without-fp
     Use this option if your computer lacks hardware floating-point support and your operating system does not emulate an FPU.

--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-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.

--without-tls
     By default the C library is built with support for thread-local storage if the used tools support it.  By using --without-tls this can be prevented though there generally is no reason since it creates compatibility problems.

--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.

--enable-lock-elision=yes
     Enable lock elision for pthread mutexes by default.

--enable-pt_chown
     The file pt_chown is a helper binary for grantpt (see Pseudo-Terminals) that is installed setuid root to fix up pseudo-terminal ownership.  It is not built by default because systems using the Linux kernel are commonly built with the devpts filesystem enabled and mounted at /dev/pts, which manages pseudo-terminal ownership automatically.  By using --enable-pt_chown, you may build pt_chown and install it setuid and owned by root.  The use of pt_chown introduces additional security risks to the system and you should enable it only if you understand and accept those risks.

--disable-werror
     By default, theglibc 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 theglibc was tested with, so new warnings cause the build with -Werror to fail), you can configure with --disable-werror.

--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 theglibc 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 CFLAGS.

     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 theglibc. 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 theglibc.  The default value refers to the main bug-reporting information for theglibc.

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 isn'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.  See 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 theglibc 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 theglibc 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: CC=TARGET-gcc configure TARGET.  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 theglibc, 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 theglibc.  The source and build directories must be visible at the same locations on both the build system and HOSTNAME.

In general, when testing theglibc, 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.

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 theglibc 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 theglibc 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 theglibc yourself after installing the library.

You can install theglibc somewhere other than where you configured it to go by setting the install_root 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.

Theglibc 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 might want to configure the timezone and locale installation of your system.  Theglibc comes with a locale database which gets configured with localedef.  For example, to set up a German locale with name de_DE, simply issue the command localedef -i de_DE -f ISO-8859-1 de_DE.  To configure all locales that are supported by theglibc, you can issue from your build directory the command make localedata/install-locales.

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 theglibc:

  * GNU make 3.79 or newer

     You need the latest version of GNU make.  Modifying theglibc to work with other make programs would be so difficult that we recommend you port GNU make instead.  Really.  We recommend GNU make version 3.79.  All earlier versions have severe bugs or lack features.

  * GCC 4.6 or newer

     GCC 4.6 or higher is required.  In general it is recommended to use the newest version of the compiler that is known to work for building theglibc, as newer compilers usually produce better code.  As of release time, GCC 4.9.2 is the newest compiler verified to work to build theglibc.

     You can use whatever compiler you like to compile programs that use theglibc.

     Check the FAQ for any special compiler issues on particular platforms.

  * GNU binutils 2.22 or later

     You must use GNU binutils (as and ld) to build theglibc. No other assembler or linker has the necessary functionality at the moment. As of release time, GNU binutils 2.25 is the newest verified to work to build theglibc.

  * 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 5.2 is the newest verified to work to build theglibc.

  * 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.

  * Perl 5

     Perl is not required, but it is used if present to test the installation.  We may decide to use it elsewhere in the future.

  * GNU sed 3.02 or newer

     Sed is used in several places to generate files.  Most scripts work with any version of sed.  The known exception is the script po2test.sed in the intl subdirectory which is used to generate msgs.h for the test suite.  This script works correctly only with GNU sed 3.02.  If you like to run the test suite, you should definitely upgrade sed.

If you change any of the configure.ac files you will also need

  * GNU autoconf 2.69 (exactly)

and if you change any of the message translation files you will need

  * GNU gettext 0.10.36 or later

If you wish to regenerate the yacc parser code in the intl subdirectory you will need

  * GNU bison 2.7 or later

You may also need these packages if you upgrade your source tree using patches, although we try to avoid this.

Specific advice for gnulinuxsystems
===================================

If you are installing theglibc on gnulinuxsystems, you need to have the header files from a 2.6.32 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 theglibc.  You do not need to use that kernel, just have its headers installed where theglibc 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 theglibc with the option --with-headers=INSTALL-DIRECTORY/include. Use the most recent kernel you can get your hands on.  (If you are cross-compiling theglibc, 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 theglibc, 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 theglibc provides its own version of /usr/include/scsi; the files provided by the kernel should be copied without replacing those provided by theglibc.  The linux, asm and asm-generic directories are required to compile programs using theglibc; 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 gnulinuxsystems expects some components of the glibcadj installation to be in /lib and some in /usr/lib.  This is handled automatically if you configure theglibc with --prefix=/usr.  If you set some other prefix or allow it to default to /usr/local, then all the components are installed there.

Reporting Bugs
==============

There are probably bugs in theglibc.  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 glibcadj bug tracking system has a WWW interface at http://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 theglibc 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 theglibc.  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 theglibc does not conform to the ISO and POSIX standards (see 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 REPORT_BUGS_TO.

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.