Installing the GNU C Library
****************************

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.

Two components of GNU Libc are distributed as add-on bundles separate from the main distribution.  Unless you are doing an unusual installation, you should get them both.  Support for the crypt function is distributed separately because of US 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.  Support for POSIX threads is maintained by someone else, so it's in a separate package. At the moment it is only available for Linux systems; 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.  Both add-on bundles should be unpacked into the top level of the libc source tree.

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

Configuring and compiling GNU Libc
==================================

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: --enable-add-ons and --prefix.  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.  The --prefix option tells configure where you want glibc installed. This defaults to /usr/local.  If you are installing glibc as your primary C library, give the option --prefix=/usr, which will put components in /usr or / as appropriate.

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:

--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 given, or /usr/local otherwise.

--with-headers=DIRECTORY
     Look for kernel header files in DIRECTORY, not /usr/include.  Glibc needs information from the kernel's private header files.  It will normally look in /usr/include for them, but if you give 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 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 /usr/include.

--enable-add-ons[=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 do want used, like this: --enable-add-ons=crypt,linuxthreads

--with-binutils=DIRECTORY
     Use the binutils (assembler and linker) in 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.  (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.)

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

--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.

--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.

--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-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.

--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.

--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.

--build=BUILD-SYSTEM
--host=HOST-SYSTEM
     These options are for cross-compiling.  If you give them both and BUILD-SYSTEM is different from HOST-SYSTEM, 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 one of these, configure will get confused.  If configure doesn't correctly guess your system type for a native build, report that as a bug.

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 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.

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.  If you want to install the files in a different place than the one specified at configuration time you can specify a value for the Makefile variable install_root on the command line. This is useful to create chroot'ed environment or to prepare binary releases.

Recommended Tools for Compilation
=================================

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

  * GNU 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.

  * 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.

  * GNU 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.

  * GNU 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 mechanisms for the info files is not present or works differently.

     On some Debian Linux based systems the install-info program supplied with the system works differently from the one we expect.  You must therefore run make install like this:

          make INSTALL_INFO=/path/to/GNU/install-info install

  * GNU 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; GNU awk 3.0 and mawk 1.3 are known to work.

  * 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.

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

  * GNU autoconf 2.12

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

  * GNU 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.

Supported Configurations
========================

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

     alpha-*-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.

While no other configurations are supported, there are handy aliases for these few.  (These aliases work in other GNU software as well.)

     decstation
     hp320-bsd4.3 hp300bsd
     i486-gnu
     i586-linux
     i386-sco
     i386-sco3.2v4
     i386-sequent-dynix
     i386-svr4
     news
     sun3-sunos4.N sun3
     sun4-solaris2.N sun4-sunos5.N
     sun4-sunos4.N sun4

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.

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.

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. When reporting a bug, send your test case, the results you got, the results you expected, what you think the problem might be (if you've thought of anything), your system type, and the version of the GNU C library which you are using.  Also include the files config.status and config.make which are created by running configure; they will be in whatever directory was current when you ran configure.

If you think you have found some way in which the GNU C library does not conform to the ISO and POSIX standards (see Standards and Portability), that is definitely a bug.  Report it!

Send bug reports to the Internet address bug-glibc@gnu.org using the glibcbug script which is installed by the GNU C library.  If you have other problems with installation or use, please report those as well.

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.