Before you do anything else, you should read the file `FAQ' found at the top level of the source tree. This file answers common questions and describes problems you may experience with compilation and installation. It is updated more frequently than this manual.
Features can be added to GNU Libc via add-on bundles. These are
separate tarfiles 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. As of the
2.2 release, one important component of glibc is distributed as
"official" add-ons: the linuxthreads add-on. Unless you are doing an
unusual installation, you should get this.
Support for POSIX threads is maintained by someone else, so it's in a separate package. It is only available for Linux systems, but this will change in the future. Get it from the same place you got the main bundle; the file is `glibc-linuxthreads-VERSION.tar.gz'.
You will need recent versions of several GNU tools: definitely GCC and GNU Make, and possibly others. See section Recommended Tools for Compilation, below.
GNU libc can be compiled in the source directory, but we strongly advise to build it in a separate build directory. For example, if you have unpacked the glibc sources in `/src/gnu/glibc-2.2.0', 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' found at the top level of the source tree. In the scenario above, you'd type
$ ../glibc-2.2.0/configure args...
Please note that even if you're building in a separate build directory, the compilation needs to modify a few files in the source directory, especially some files in the manual subdirectory.
configure takes many options, but you can get away with knowing
only two: `--prefix' and `--enable-add-ons'. The
--prefix option tells configure where you want glibc installed.
This defaults to `/usr/local'. The `--enable-add-ons' option
tells configure to use all the add-on bundles it finds in the source
directory. Since important functionality is provided in add-ons, you
should always specify this option.
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:
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.
configure
will prepare to cross-compile glibc 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 i586-pc-linux-gnu but you want
to compile a library for 386es, give `--host=i386-pc-linux-gnu' or
just `--host=i386-linux' and add the appropriate compiler flags
(`-mcpu=i386' will do the trick) to CFLAGS.
If you specify just `--build', configure will get confused.
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 really wrong.
The compilation process takes several hours even on fast hardware. Expect at least two hours for the default configuration on i586 for Linux. For Hurd times are much longer. Except for EGCS 1.1 and GCC 2.95 (and later versions of GCC), all supported versions of GCC have a problem which causes them to take several minutes to compile certain files in the iconvdata directory. Do not panic if the compiler appears to hang.
If you want to run a parallel make, you can't just give make the
`-j' option, because it won't be passed down to the sub-makes.
Instead, edit the generated `Makefile' and uncomment the line
# PARALLELMFLAGS = -j 4
You can change the `4' to some other number as appropriate for
your system. Instead of changing the `Makefile', you could give
this option directly to make and call it as, for example,
make PARALLELMFLAGS=-j4. If you're building in the source
directory, you must use the latter approach since in this case no
new `Makefile' is generated for you to change.
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 section 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 glibc as an unprivileged user.
To format the GNU C Library Reference Manual for printing, type
make dvi. You need a working TeX installation to do this.
The distribution already includes the on-line formatted version of the
manual, as Info files. You can regenerate those with make
info, but it shouldn't be necessary.
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: `CC=target-gcc configure
target'. Set BUILD_CC to the compiler to use for for
programs run on the build system as part of compiling the library. You
may need to set AR and RANLIB to cross-compiling versions
of ar and ranlib if the native tools are not configured to
work with object files for the target you configured for.
To install the library and its header files, and the Info files of the
manual, type env LANGUAGE=C LC_ALL=C make install. This will
build things if necessary, before installing them. However, you should
still compile everything first. If you are installing glibc 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.
If you're upgrading from Linux libc5 or some other C library, you need to replace the `/usr/include' with a fresh directory before installing it. The new `/usr/include' should contain the Linux headers, but nothing else.
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.
If you are upgrading from a previous installation of glibc 2.0 or 2.1, `make install' will do the entire job. You do not need to remove the old includes -- if you want to do so anyway you must then follow the order given above.
You may also need to reconfigure GCC to work with the new library. The easiest way to do that is to figure out the compiler switches to make it work again (`-Wl,--dynamic-linker=/lib/ld-linux.so.2' should work on Linux systems) and use them to recompile gcc. You can also edit the specs file (`/usr/lib/gcc-lib/TARGET/VERSION/specs'), but that is a bit of a black art.
You can install glibc 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.
Glibc 2.2 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. This program is invoked by the grantpt function; it
sets the permissions on a pseudoterminal so it can be used by the
calling process. This means programs like xterm and
screen do not have to be setuid to get a pty. (There may be
other reasons why they need privileges.) If you are using a 2.1 or
newer Linux kernel with the devptsfs or devfs filesystems
providing pty slaves, you don't need this program; otherwise you do.
The source for `pt_chown' is in `login/programs/pt_chown.c'.
After installation you might want to configure the timezone and locale
installation of your system. The GNU C library 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 glibc, you can issue from your build directory the
command `make localedata/install-locales'.
To configure the locally used timezone, you can either 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'.
We recommend installing the following GNU tools before attempting to build the GNU C library:
make 3.79 or newer
You need the latest version of GNU make. Modifying the GNU C
Library to work with other make programs would be so difficult that we
recommend you port GNU make instead. Really. We
recommend version GNU make version 3.79. All earlier
versions have severe bugs or lack features.
binutils 2.10.1 or later
You must use GNU binutils (as and ld) if you want to build a shared
library. Even if you don't, we recommend you use them anyway. No one
has tested compilation with non-GNU binutils in a long time.
The quality of binutils releases has varied a bit recently. The bugs
are in obscure features, but glibc uses quite a few of those. 2.10.1
and later releases are known to work. Versions after 2.8.1.0.23 may or
may not work. Older versions definitely don't.
For PPC you might need some patches even on top of the last binutils
version. See the FAQ.
texinfo 3.12f
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.
awk 3.0, or some other POSIX awk
Awk is used in several places to generate files. The scripts should
work with any POSIX-compliant awk implementation; gawk 3.0 and
mawk 1.3 are known to work.
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 testsuite. This script works correctly
only with GNU sed 3.02. If you like to run the testsuite, you
should definitely upgrade sed.
If you change any of the `configure.in' files you will also need
autoconf 2.12 or higher
and if you change any of the message translation files you will need
gettext 0.10.36 or later
You may also need these packages if you upgrade your source tree using patches, although we try to avoid this.
The GNU C Library currently supports configurations that match the following patterns:
alpha*-*-linux arm-*-linux cris-*-linux hppa-*-linux ix86-*-gnu ix86-*-linux ia64-*-linux m68k-*-linux mips*-*-linux powerpc-*-linux s390-*-linux s390x-*-linux sparc-*-linux sparc64-*-linux
Former releases of this library (version 2.1 and/or 2.0) used to run on the following configurations:
arm-*-linuxaout arm-*-none
Very early releases (version 1.09.1 and perhaps earlier versions) used to run on the following configurations:
alpha-dec-osf1 alpha-*-linuxecoff ix86-*-bsd4.3 ix86-*-isc2.2 ix86-*-isc3.n ix86-*-sco3.2 ix86-*-sco3.2v4 ix86-*-sysv ix86-*-sysv4 ix86-force_cpu386-none ix86-sequent-bsd i960-nindy960-none m68k-hp-bsd4.3 m68k-mvme135-none m68k-mvme136-none m68k-sony-newsos3 m68k-sony-newsos4 m68k-sun-sunos4.n mips-dec-ultrix4.n mips-sgi-irix4.n sparc-sun-solaris2.n sparc-sun-sunos4.n
Since no one has volunteered to test and fix these configurations, they are not supported at the moment. They probably don't compile; they definitely don't work anymore. Porting the library is not hard. If you are interested in doing a port, please contact the glibc maintainers by sending electronic mail to @email{bug-glibc@gnu.org}.
Valid cases of `ix86' include `i386', `i486', `i586', and `i686'. All of those configurations produce a library that can run on this processor and newer processors. The GCC compiler by default generates code that's optimized for the machine it's configured for and will use the instructions available on that machine. For example if your GCC is configured for `i686', gcc will optimize for `i686' and might issue some `i686' specific instructions. To generate code for other models, you have to configure for that model and give GCC the appropriate `-march=' and `-mcpu=' compiler switches via CFLAGS.
If you are installing GNU libc on a Linux system, you need to have the header files from a 2.2 kernel around for reference. You do not need to use the 2.2 kernel, just have its headers where glibc can access at them. The easiest way to do this is to unpack it in a directory such as `/usr/src/linux-2.2.1'. In that directory, run `make config' and accept all the defaults. Then run `make include/linux/version.h'. Finally, configure glibc with the option `--with-headers=/usr/src/linux-2.2.1/include'. Use the most recent kernel you can get your hands on.
An alternate tactic is to unpack the 2.2 kernel and run `make config' as above. Then rename or delete `/usr/include', create a new `/usr/include', and make the usual symbolic links of `/usr/include/linux' and `/usr/include/asm' into the 2.2 kernel sources. You can then configure glibc with no special options. This tactic is recommended if you are upgrading from libc5, since you need to get rid of the old header files anyway.
Note that `/usr/include/net' and `/usr/include/scsi' should not be symlinks into the kernel sources. GNU libc provides its own versions of these files.
Linux expects some components of the libc installation to be in `/lib' and some in `/usr/lib'. This is handled automatically if you configure glibc with `--prefix=/usr'. If you set some other prefix or allow it to default to `/usr/local', then all the components are installed there.
If you are upgrading from libc5, you need to recompile every shared library on your system against the new library for the sake of new code, but keep the old libraries around for old binaries to use. This is complicated and difficult. Consult the Glibc2 HOWTO at @url{http://www.imaxx.net/~thrytis/glibc} for details.
You cannot use nscd with 2.0 kernels, due to bugs in the
kernel-side thread support. nscd happens to hit these bugs
particularly hard, but you might have problems with any threaded
program.
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 bug tracking system has a WWW interface at @url{http://www-gnats.gnu.org:8080/cgi-bin/wwwgnats.pl}. The WWW interface gives you access to open and closed reports. The closed reports normally include a patch or a hint on solving the problem.
To report a bug, first you must find it. Hopefully, 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 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 (see section 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 using the glibcbug script. It is installed with libc, or
if you haven't installed it, will be in your build directory. Send your
test case, the results you got, the results you expected, and what you
think the problem might be (if you've thought of anything).
glibcbug will insert the configuration information we need to
see, and ship the report off to @email{bugs@gnu.org}. Don't send
a message there directly; it is fed to a program that expects mail to be
formatted in a particular way. Use the script.
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 Internet address @email{bug-glibc-manual@gnu.org}. If you refer to specific sections of the manual, please include the section names for easier identification.
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