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Configuring and compiling GNU Libc

GNU Libc can be compiled in the source directory but we'd advise to build in a separate build directory. 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:

`--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 `--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.


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