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

Installation of the GNU C library is relatively simple, but usually requires several GNU tools to be installed already.

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.

To configure the GNU C library for your system, run the shell script configure with sh.  You might use an argument which is the conventional GNU name for your system configuration---for example, i486-pc-linux-gnu, for Linux running on i486. See Installing GNU CC (Using and Porting GNU CC), for a full description of standard GNU configuration names.  If you omit the configuration name, configure will try to guess one for you by inspecting the system it is running on.  It may or may not be able to come up with a guess, and the guess might be wrong.  configure will tell you the canonical name of the chosen configuration before proceeding.

Here are some options that you should specify (if appropriate) when you run configure:

--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
--nfp

     Use this option if your computer lacks hardware floating-point support and your operating system does not emulate an FPU.

--prefix=DIRECTORY
     Install machine-independent data files in subdirectories of DIRECTORY.  (You can also set this in configparms; see below.)  The default is to install in `/usr/local'.

--exec-prefix=DIRECTORY
     Install the library and other machine-dependent files in subdirectories of DIRECTORY.  (You can also set this in configparms; see below.)  The default is to use <prefix>/bin and <prefix>/sbin.

--enable-shared
--disable-shared
     Enable or disable building of an ELF shared library on systems that support it.  The default is to build the shared library on systems using ELF when the GNU binutils are available.

--enable-profile
--disable-profile
     Enable or disable building of the profiled C library, -lc_p.  The default is to build the profiled library.  You may wish to disable it if you don't plan to do profiling, because it doubles the build time of compiling just the unprofiled static library.

--enable-omitfp
     Enable building a highly-optimized but possibly undebuggable C library.  This causes the normal static and shared (if enabled) C libraries to be compiled with maximal optimization, including the -fomit-frame-pointer switch that makes debugging impossible on many machines, and without debugging information (which makes the binaries substantially smaller).  An additional static library is compiled with no optimization and full debugging information, and installed as -lc_g.

--enable-add-ons[=LIST]
     Certain components of the C library are distributed separately from the rest of the sources.  In particular, the crypt function and its friends are separated due to US export control regulations, and the threading support code for Linux is maintained separately.  You can get these add-on packages from the same place you got the libc sources.  To use them, unpack them into your source tree, and give configure the --enable-add-ons option.

     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

You should not build the library in the same directory as the sources, because there are bugs in make clean.  Make a directory for the build, and run configure from that directory, like this:

     mkdir linux
     cd linux
     ../configure

configure looks for the sources in whatever directory you specified for finding configure itself.  It does not matter where in the file system the source and build directories are---as long as you specify the source directory when you run configure, you will get the proper results.

This feature lets you keep sources and binaries in different directories, and that makes it easy to build the library for several different machines from the same set of sources.  Simply create a build directory for each target machine, and run configure in that directory specifying the target machine's configuration name.

The library has a number of special-purpose configuration parameters. These are defined in the file configparms; see the comments in that file for the details.  To change them, copy configparms into your build directory and modify it as appropriate for your system. configure will not notice your modifications if you change the file in the source directory.

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.

Some of the machine-dependent code for some machines uses extensions in the GNU C compiler, so you may need to compile the library with GCC. (In fact, all of the existing complete ports require GCC.)

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.

To build and run some test programs which exercise some of the library facilities, type make check.  This will produce several files with names like PROGRAM.out.

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.

For now (in this alpha version, and at least on RedHat Linux), if you are trying to install this as your default libraries, a different installation method is recommended.  Move /usr/include out of the way, create a new /usr/include directory (don't forget the symlinks /usr/include/asm and /usr/include/linux, that should point to /usr/src/linux/include/asm and /usr/src/linux/include/linux -or wherever you keep your kernel sources-respectively), build normally and install into somewhere else via install_root. Then move your /usr/include back, and copy the newly created stuff by hand over the old. Remember to copy programs and shared libraries into FILENAME.new and then move FILENAME.new to FILENAME, as the files might be in use. You will have to ranlib your copies of the static libraries /usr/lib/libNAME.a. You will see that libbsd-compat.a, libieee.a, and libmcheck.a are just object files, not archives. This is normal.  Copy the new header files over the old ones by something like cd /usr; (cd INSTALL_ROOT; tar cf - include) | tar xf -.

Recommended Tools to Install the GNU C Library
==============================================

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.  Versions 3.76 and 3.76.1 are known to have bugs which only show up in big projects like GNU libc.

  * GCC 2.8.1/EGCS 1.0.2

     On most platforms, the GNU C library can only be compiled with the GNU C compiler family.  We recommend GCC version 2.8.1 and EGCS version 1.0.2 or later versions of these two; earlier versions may have problems.

  * GNU binutils 2.8.1.0.23

     Using the GNU binutils (assembler, linker, and related tools) is preferable when possible, and they are required to build an ELF shared C library.  Version 2.1 of the library uses ELF symbol versioning extensively.  Support for this feature is incomplete or buggy before binutils 2.8.1.0.23, so you must use at least this version.

  * 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

     Several files used during the build are generated using features of GNU awk that are not found in other implementations.

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 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-ANYTHING-linux
     arm-ANYTHING-linuxaout
     arm-ANYTHING-none
     iX86-ANYTHING-gnu
     iX86-ANYTHING-linux
     m68k-ANYTHING-linux
     powerpc-ANYTHING-linux
     sparc-ANYTHING-linux
     sparc64-ANYTHING-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-ANYTHING-linuxecoff
     iX86-ANYTHING-bsd4.3
     iX86-ANYTHING-isc2.2
     iX86-ANYTHING-isc3.N
     iX86-ANYTHING-sco3.2
     iX86-ANYTHING-sco3.2v4
     iX86-ANYTHING-sysv
     iX86-ANYTHING-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

Useful hints for the installation
=================================

There are a some more or less obvious methods one should know when compiling GNU libc:

  * Better never compile in the source directory.  Create a new directory and run the configure from there.  Everything should happen automagically.

  * You can use the -j option of GNU make by changing the line specifying PARALLELMAKE in the Makefile generated during the configuration.

     It is not useful to start the make process using the -j option since this option is not propagated down to the sub-makes.

  * If you made some changes after a complete build and only want to check these changes run make while specifying the list of subdirs it has to visit.

          make subdirs="nss elf"

     The above build run will only visit the subdirectories nss and elf.  Beside this it updates the libc files itself.

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.