@c This is for making the `INSTALL' file for the distribution.
@c Makeinfo ignores it when processing the file from the include.
@setfilename INSTALL

@node Installation, Maintenance, Library Summary, Top
@c %MENU% How to install the GNU C library
@appendix Installing the GNU C Library

Before you do anything else, you should read the file @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 @dfn{add-on} bundles.  These are
separate tarfiles which you unpack into the top level of the source
tree.  Then you give @code{configure} the @samp{--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 @file{glibc-linuxthreads-@var{VERSION}.tar.gz}.
Support for the @code{crypt} function is distributed separately because
of United States export restrictions.  If you are outside the US or
Canada, you must get @code{crypt} support from a site outside the US,
such as @samp{ftp.ifi.uio.no}.
@c Check this please someone:
(Most non-US mirrors of @samp{ftp.gnu.org} will have it too.)  The file
you need is @file{glibc-crypt-@var{VERSION}.tar.gz}.  

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

@menu
* Configuring and compiling::   How to compile and test GNU libc.
* Installation::                How to install it once you've got it compiled.
* Tools for Compilation::       You'll need these first.
* Supported Configurations::    What it runs on, what it doesn't.
* Linux::                       Specific advice for Linux systems.
* Reporting Bugs::              So they'll get fixed.
@end menu

@node Configuring and compiling
@appendixsec Configuring and compiling GNU Libc
@cindex configuring
@cindex compiling

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 @file{/src/gnu/glibc-2.1.0}, create a directory
@file{/src/gnu/glibc-build} to put the object files in.

From your object directory, run the shell script @file{configure} found
at the top level of the source tree.  In the scenario above, you'd type

@smallexample
$ ../glibc-2.1.0/configure @var{args...}
@end smallexample

@noindent
@code{configure} takes many options, but you can get away with knowing
only two: @samp{--prefix} and @samp{--enable-add-ons}.  The
@code{--prefix} option tells configure where you want glibc installed.
This defaults to @file{/usr/local}.  The @samp{--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 @var{CC} and @var{CFLAGS} variables in
the environment when running @code{configure}.  @var{CC} selects the C
compiler that will be used, and @var{CFLAGS} sets optimization options
for the compiler.

Here are all the useful options known by @code{configure}:

@table @samp
@item --prefix=@var{directory}
Install machine-independent data files in subdirectories of
@file{@var{directory}}.  The default is to install in @file{/usr/local}.

@item --exec-prefix=@var{directory}
Install the library and other machine-dependent files in subdirectories
of @file{@var{directory}}.  The default is to the @samp{--prefix}
directory if that option is given, or @file{/usr/local} otherwise.

@item --with-headers=@var{directory}
Look for kernel header files in @var{directory}, not
@file{/usr/include}.  Glibc needs information from the kernel's private
header files.  It will normally look in @file{/usr/include} for them,
but if you give this option, it will look in @var{DIRECTORY} instead.

This option is primarily of use on a system where the headers in
@file{/usr/include} come from an older version of glibc.  Conflicts can
occasionally happen in this case.  Note that Linux libc5 qualifies as an
older version of glibc.  You can also use this option if you want to
compile glibc with a newer set of kernel headers than the ones found in
@file{/usr/include}.

@item --enable-add-ons[=@var{list}]
Enable add-on packages in your source tree.  If this option is given
with no list, it enables all the add-on packages it finds.  If you do
not wish to use some add-on package that you have present in your source
tree, give this option a list of the add-ons that you @emph{do} want
used, like this: @samp{--enable-add-ons=crypt,linuxthreads}

@item --with-binutils=@var{directory}
Use the binutils (assembler and linker) in @file{@var{directory}}, not
the ones the C compiler would default to.  You could use this option if
the default binutils on your system cannot deal with all the constructs
in the GNU C library.  (@code{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.)

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

@item --disable-static
Don't build static libraries.  Static libraries aren't that useful these
days, but we recommend you build them in case you need them.

@item --disable-shared
Don't build shared libraries even if we could.  Not all systems support
shared libraries; you need ELF support and (currently) the GNU linker.

@item --disable-profile
Don't build libraries with profiling information.  You may want to use
this option if you don't plan to do profiling.

@item --enable-omitfp
Use maximum optimization for the normal (static and shared)
libraries, and compile separate static libraries with debugging
information and no optimisation.  We recommend against this.  The extra
optimization doesn't gain you much, it may provoke compiler bugs, and
you won't be able to trace bugs through the C library.

@item --disable-versioning
Don't compile the shared libraries with symbol version information.
Doing this will make the library that's built incompatible with old
binaries, so it's not recommended.

@item --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.

@item --build=@var{build-system}
@itemx --host=@var{host-system}
These options are for cross-compiling.  If you give them both and
@var{build-system} is different from @var{host-system}, @code{configure}
will prepare to cross-compile glibc from @var{build-system} to be used
on @var{host-system}.  You'll probably need the @samp{--with-headers}
option too, and you may have to override @var{configure}'s selection of
the compiler and/or binutils.

If you give just @samp{--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 @code{i586-pc-linux-gnu} but you want
to compile a library optimized for 386es, give
@samp{--host=i386-pc-linux-gnu} or just @samp{--host=i386-linux}.  (A
library compiled for a Pentium (@code{i586}) will still work on a 386,
but it may be slower.)

If you give just @samp{--build}, configure will get confused.
@end table

To build the library and related programs, type @code{make}.  This will
produce a lot of output, some of which may look like errors from
@code{make} but isn't.  Look for error messages from @code{make}
containing @samp{***}.  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 @code{make} the
@samp{-j} option, because it won't be passed down to the sub-makes.
Instead, edit the generated @file{Makefile} and uncomment the line

@smallexample
# PARALLELMFLAGS = -j 4
@end smallexample

@noindent
You can change the @samp{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 @code{make check}.  This should complete successfully;
if it doesn't, do not use the built library, and report a bug.
@xref{Reporting Bugs}, for how to do that.  Note that some of the tests
assume they are not being run by @code{root}.  We recommend you compile
and test glibc as an unprivileged user.

To format the @cite{GNU C Library Reference Manual} for printing, type
@w{@code{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 @w{@code{make
info}}, but it shouldn't be necessary.

@node Installation
@appendixsec Installing the C Library
@cindex installing

To install the library and its header files, and the Info files of the
manual, type @code{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,
@samp{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
@file{/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
(@samp{-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 (@file{/usr/lib/gcc-lib/@var{TARGET}/@var{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 @code{install_root} variable on the command line for
@samp{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, @code{nscd} and @code{utmpd}, which you
may or may not want to run.  @code{nscd} caches name service lookups; it
can dramatically improve performance with NIS+, and may help with DNS as
well.  @code{utmpd} allows programs that use the old format for the
@file{utmp} file to coexist with new programs.  For more information see
the files @file{nscd/README} and @file{login/README.utmpd}.

One auxiliary program, @file{/usr/libexec/pt_chown}, is installed setuid
@code{root}.  This program is invoked by the @code{grantpt} function; it
sets the permissions on a pseudoterminal so it can be used by the
calling process.  This means programs like @code{xterm} and
@code{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 @code{devptsfs} or @code{devfs} filesystems providing
pty slaves, you don't need this program; otherwise you do.  The source
for @file{pt_chown} is in @file{login/programs/pt_chown.c}.

@node Tools for Compilation
@appendixsec Recommended Tools for Compilation
@cindex installation tools
@cindex tools, for installing library

We recommend installing the following GNU tools before attempting to
build the GNU C library:

@itemize @bullet
@item
GNU @code{make} 3.75

You need the latest version of GNU @code{make}.  Modifying the GNU C
Library to work with other @code{make} programs would be so hard that we
recommend you port GNU @code{make} instead.  @strong{Really.}  We
recommend version GNU @code{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 @code{libc}.
Version 3.76.1 seems OK but some people have reported problems.

@item
EGCS 1.1 or 1.0.3

The GNU C library can only be compiled with the GNU C compiler family.
We recommend EGCS 1.0.3 or higher.  GCC 2.8.1 and older versions of EGCS
may have problems, particularly on non-Intel architectures.  GCC 2.7.x
has catastrophic bugs and cannot be used at all.  (You can use GCC 2.7.x
to compile programs that use GNU libc, but you may have problems,
particularly with the math functions.)

@item
GNU @code{binutils} 2.8.1.0.23, 2.9.1, or 2.9.0.15

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.
2.8.1.0.23, 2.9.1, and 2.9.0.15 are known to work.  Versions after
2.8.1.0.23 may or may not work.  Older versions definitely don't.

@item
GNU @code{texinfo} 3.11

To correctly translate and install the Texinfo documentation you need
this version of the @code{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.

@item
GNU @code{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; @code{gawk} 3.0 and
@code{mawk} 1.3 are known to work.

@item
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.

@end itemize

@noindent
If you change any of the @file{configure.in} files you will also need

@itemize @bullet
@item
GNU @code{autoconf} 2.12
@end itemize

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

@itemize @bullet
@item
GNU @code{gettext} 0.10.35 or later
@end itemize

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

@node Supported Configurations
@appendixsec Supported Configurations
@cindex configurations, all supported

The GNU C Library currently supports configurations that match the
following patterns:

@smallexample
alpha-@var{*}-linux
arm-@var{*}-linux
arm-@var{*}-linuxaout
arm-@var{*}-none
i@var{x}86-@var{*}-gnu
i@var{x}86-@var{*}-linux
m68k-@var{*}-linux
powerpc-@var{*}-linux
sparc-@var{*}-linux
sparc64-@var{*}-linux
@end smallexample

Former releases of this library (version 1.09.1 and perhaps earlier
versions) used to run on the following configurations:

@smallexample
alpha-dec-osf1
alpha-@var{*}-linuxecoff
i@var{x}86-@var{*}-bsd4.3
i@var{x}86-@var{*}-isc2.2
i@var{x}86-@var{*}-isc3.@var{n}
i@var{x}86-@var{*}-sco3.2
i@var{x}86-@var{*}-sco3.2v4
i@var{x}86-@var{*}-sysv
i@var{x}86-@var{*}-sysv4
i@var{x}86-force_cpu386-none
i@var{x}86-sequent-bsd
i960-nindy960-none
m68k-hp-bsd4.3
m68k-mvme135-none
m68k-mvme136-none
m68k-sony-newsos3
m68k-sony-newsos4
m68k-sun-sunos4.@var{n}
mips-dec-ultrix4.@var{n}
mips-sgi-irix4.@var{n}
sparc-sun-solaris2.@var{n}
sparc-sun-sunos4.@var{n}
@end smallexample

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}.

Each case of @samp{i@var{x}86} can be @samp{i386}, @samp{i486},
@samp{i586}, or @samp{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 @samp{-m}
switches via @var{CFLAGS}.

@node Linux
@appendixsec Specific advice for Linux systems
@cindex upgrading from libc5
@cindex kernel header files

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 @file{/usr/src/linux-dev}.  In that
directory, run @samp{make config} and accept all the defaults.  Then
configure glibc with the option
@samp{--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
@samp{make config} as above.  Then rename or delete @file{/usr/include},
create a new @file{/usr/include}, and make the usual symbolic links of
@file{/usr/include/linux} and @file{/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 @file{/usr/include/net} and @file{/usr/include/scsi} should
@strong{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
@file{/lib} and some in @file{/usr/lib}.  This is handled automatically
if you configure glibc with @samp{--prefix=/usr}.  If you set some other
prefix or allow it to default to @file{/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 @code{nscd} with 2.0 kernels, due to bugs in the
kernel-side thread support.  @code{nscd} happens to hit these bugs
particularly hard, but you might have problems with any threaded
program.

@node Reporting Bugs
@appendixsec Reporting Bugs
@cindex reporting bugs
@cindex bugs, reporting

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 (@pxref{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 @code{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).
@code{glibcbug} will insert the configuration information we need to
see, and ship the report off to @email{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 @email{bug-glibc-manual@@gnu.org}.  If you refer to specific
sections when reporting on the manual, please include the section names
for easier identification.