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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
2.1 release, two important components of glibc are distributed as
"official" add-ons. Unless you are doing an unusual installation, you
should get them both.
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'.
Support for the crypt
function is distributed separately because
of United States export restrictions. If you are outside the US or
Canada, you must get crypt
support from a site outside the US,
such as `ftp.ifi.uio.no'.
(Most non-US mirrors of `ftp.gnu.org' will have it too.) The file
you need is `glibc-crypt-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 cannot be compiled in the source directory. You must create a separate directory for the object files. This directory should be outside the source tree. For example, if you have unpacked the glibc sources in `/src/gnu/glibc-2.1.0', create a directory `/src/gnu/glibc-build' to put the object files in.
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-2.1.0/configure args...
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 give 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.
Here are all the useful options known by configure
:
configure
will detect the problem and
suppress these constructs, so the library will still be usable, but
functionality may be lost--for example, you can not 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 give just `--host', configure will prepare for a native
compile but use what you say 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 optimized for 386es, give
`--host=i386-pc-linux-gnu' or just `--host=i386-linux'. (A
library compiled for a Pentium (i586
) will still work on a 386,
but it may be slower.)
If you give 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 later versions of EGCS), 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.
To build and run some test programs which exercise some of the library
facilities, type make check
. This should complete successfully;
if it doesn't, do not use the built library, and report a bug.
See section Reporting Bugs, for how to do that. 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.
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. Don't rely on that; compile everything first.
If you are installing glibc as your primary C library, we recommend 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 are upgrading from a previous installation of glibc 2.0 or 2.1, `make install' will do the entire job. If you're upgrading from Linux libc5 or some other C library, you need to rename the old `/usr/include' directory out of the way first, or you will end up with a mixture of header files from both libraries, and you won't be able to compile anything. 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.
Glibc 2.1 includes two daemons, nscd
and utmpd
, 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. utmpd
allows programs that use the old format for the
`utmp' file to coexist with new programs. For more information see
the files `nscd/README' and `login/README.utmpd'.
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 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'.
We recommend installing the following GNU tools before attempting to build the GNU C library:
make
3.75
You need the latest version of GNU make
. Modifying the GNU C
Library to work with other make
programs would be so hard that we
recommend you port GNU make
instead. Really. We
recommend version GNU make
version 3.75 or 3.77. All earlier
versions have severe bugs or lack features. Version 3.76 is known to
have bugs which only show up in big projects like GNU libc
.
Version 3.76.1 seems OK but some people have reported problems.
binutils
2.9.1, or 2.9.1.0.16
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.
2.9.1 and 2.9.1.0.16 are known to work. Versions after
2.8.1.0.23 may or may not work. Older versions definitely don't.
2.9.1.0.16 is required on some platforms, like PPC and Arm.
For PPC you might need some patches even on top of the last binutils
version. See the FAQ.
texinfo
3.11
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.
If you change any of the `configure.in' files you will also need
autoconf
2.12
and if you change any of the message translation files you will need
gettext
0.10.35 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 arm-*-linuxaout arm-*-none ix86-*-gnu ix86-*-linux m68k-*-linux powerpc-*-linux sparc-*-linux sparc64-*-linux
Former releases of this library (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 bug-glibc@gnu.org.
Each case of `ix86' can be `i386', `i486', `i586', or `i686'. All of those configurations produce a library that can run on any of these processors. The library will be optimized for the specified processor, but will not use instructions not available on all of them. If you want the library to use instructions only available on newer processors, give GCC the appropriate `-m' switches via CFLAGS.
If you are installing GNU libc on a Linux system, you need to have the header files from a development kernel around for reference. You do not need to use the development kernel, just have its headers where glibc can get at them. The easiest way to do this is to unpack a development kernel in a directory such as `/usr/src/linux-dev'. In that directory, run `make config' and accept all the defaults. Then configure glibc with the option `--with-headers=/usr/src/linux-dev/include'. Use the latest development kernel you can get your hands on.
An alternate tactic is to unpack the development 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 development 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
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.
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 bug-glibc@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 bug-glibc-manual@gnu.org. If you refer to specific sections when reporting on the manual, please include the section names for easier identification.
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