1 Installing the GNU C Library
2 ****************************
4 Before you do anything else, you should read the file `FAQ' located at
5 the top level of the source tree. This file answers common questions
6 and describes problems you may experience with compilation and
7 installation. It is updated more frequently than this manual.
9 Features can be added to GNU Libc via "add-on" bundles. These are
10 separate tar files, which you unpack into the top level of the source
11 tree. Then you give `configure' the `--enable-add-ons' option to
12 activate them, and they will be compiled into the library.
14 You will need recent versions of several GNU tools: definitely GCC
15 and GNU Make, and possibly others. *Note Tools for Compilation::,
18 Configuring and compiling GNU Libc
19 ==================================
21 GNU libc cannot be compiled in the source directory. You must build it
22 in a separate build directory. For example, if you have unpacked the
23 glibc sources in `/src/gnu/glibc-2.4', create a directory
24 `/src/gnu/glibc-build' to put the object files in. This allows
25 removing the whole build directory in case an error occurs, which is
26 the safest way to get a fresh start and should always be done.
28 From your object directory, run the shell script `configure' located
29 at the top level of the source tree. In the scenario above, you'd type
31 $ ../glibc-2.4/configure ARGS...
33 Please note that even though you're building in a separate build
34 directory, the compilation needs to modify a few files in the source
35 directory, especially some files in the manual subdirectory.
37 `configure' takes many options, but the only one that is usually
38 mandatory is `--prefix'. This option tells `configure' where you want
39 glibc installed. This defaults to `/usr/local', but the normal setting
40 to install as the standard system library is `--prefix=/usr' for
41 GNU/Linux systems and `--prefix=' (an empty prefix) for GNU/Hurd
44 It may also be useful to set the CC and CFLAGS variables in the
45 environment when running `configure'. CC selects the C compiler that
46 will be used, and CFLAGS sets optimization options for the compiler.
48 The following list describes all of the available options for
52 Install machine-independent data files in subdirectories of
53 `DIRECTORY'. The default is to install in `/usr/local'.
55 `--exec-prefix=DIRECTORY'
56 Install the library and other machine-dependent files in
57 subdirectories of `DIRECTORY'. The default is to the `--prefix'
58 directory if that option is specified, or `/usr/local' otherwise.
60 `--with-headers=DIRECTORY'
61 Look for kernel header files in DIRECTORY, not `/usr/include'.
62 Glibc needs information from the kernel's private header files.
63 Glibc will normally look in `/usr/include' for them, but if you
64 specify this option, it will look in DIRECTORY instead.
66 This option is primarily of use on a system where the headers in
67 `/usr/include' come from an older version of glibc. Conflicts can
68 occasionally happen in this case. Note that Linux libc5 qualifies
69 as an older version of glibc. You can also use this option if you
70 want to compile glibc with a newer set of kernel headers than the
71 ones found in `/usr/include'.
73 `--enable-add-ons[=LIST]'
74 Specify add-on packages to include in the build. If this option is
75 specified with no list, it enables all the add-on packages it
76 finds in the main source directory; this is the default behavior.
77 You may specify an explicit list of add-ons to use in LIST,
78 separated by spaces or commas (if you use spaces, remember to
79 quote them from the shell). Each add-on in LIST can be an
80 absolute directory name or can be a directory name relative to the
81 main source directory, or relative to the build directory (that
82 is, the current working directory). For example,
83 `--enable-add-ons=nptl,../glibc-libidn-2.4'.
85 `--enable-kernel=VERSION'
86 This option is currently only useful on GNU/Linux systems. The
87 VERSION parameter should have the form X.Y.Z and describes the
88 smallest version of the Linux kernel the generated library is
89 expected to support. The higher the VERSION number is, the less
90 compatibility code is added, and the faster the code gets.
92 `--with-binutils=DIRECTORY'
93 Use the binutils (assembler and linker) in `DIRECTORY', not the
94 ones the C compiler would default to. You can use this option if
95 the default binutils on your system cannot deal with all the
96 constructs in the GNU C library. In that case, `configure' will
97 detect the problem and suppress these constructs, so that the
98 library will still be usable, but functionality may be lost--for
99 example, you can't build a shared libc with old binutils.
102 Use this option if your computer lacks hardware floating-point
103 support and your operating system does not emulate an FPU.
108 Don't build shared libraries even if it is possible. Not all
109 systems support shared libraries; you need ELF support and
110 (currently) the GNU linker.
113 Don't build libraries with profiling information. You may want to
114 use this option if you don't plan to do profiling.
117 Use maximum optimization for the normal (static and shared)
118 libraries, and compile separate static libraries with debugging
119 information and no optimization. We recommend not doing this.
120 The extra optimization doesn't gain you much, it may provoke
121 compiler bugs, and you won't be able to trace bugs through the C
124 `--disable-versioning'
125 Don't compile the shared libraries with symbol version information.
126 Doing this will make the resulting library incompatible with old
127 binaries, so it's not recommended.
129 `--enable-static-nss'
130 Compile static versions of the NSS (Name Service Switch) libraries.
131 This is not recommended because it defeats the purpose of NSS; a
132 program linked statically with the NSS libraries cannot be
133 dynamically reconfigured to use a different name database.
136 By default the C library is built with support for thread-local
137 storage if the used tools support it. By using `--without-tls'
138 this can be prevented though there generally is no reason since it
139 creates compatibility problems.
141 `--build=BUILD-SYSTEM'
143 These options are for cross-compiling. If you specify both
144 options and BUILD-SYSTEM is different from HOST-SYSTEM, `configure'
145 will prepare to cross-compile glibc from BUILD-SYSTEM to be used
146 on HOST-SYSTEM. You'll probably need the `--with-headers' option
147 too, and you may have to override CONFIGURE's selection of the
148 compiler and/or binutils.
150 If you only specify `--host', `configure' will prepare for a
151 native compile but use what you specify instead of guessing what
152 your system is. This is most useful to change the CPU submodel.
153 For example, if `configure' guesses your machine as
154 `i586-pc-linux-gnu' but you want to compile a library for 386es,
155 give `--host=i386-pc-linux-gnu' or just `--host=i386-linux' and add
156 the appropriate compiler flags (`-mcpu=i386' will do the trick) to
159 If you specify just `--build', `configure' will get confused.
161 To build the library and related programs, type `make'. This will
162 produce a lot of output, some of which may look like errors from `make'
163 but isn't. Look for error messages from `make' containing `***'.
164 Those indicate that something is seriously wrong.
166 The compilation process can take a long time, depending on the
167 configuration and the speed of your machine. Some complex modules may
168 take a very long time to compile, as much as several minutes on slower
169 machines. Do not panic if the compiler appears to hang.
171 If you want to run a parallel make, simply pass the `-j' option with
172 an appropriate numeric parameter to `make'. You need a recent GNU
173 `make' version, though.
175 To build and run test programs which exercise some of the library
176 facilities, type `make check'. If it does not complete successfully,
177 do not use the built library, and report a bug after verifying that the
178 problem is not already known. *Note Reporting Bugs::, for instructions
179 on reporting bugs. Note that some of the tests assume they are not
180 being run by `root'. We recommend you compile and test glibc as an
183 Before reporting bugs make sure there is no problem with your system.
184 The tests (and later installation) use some pre-existing files of the
185 system such as `/etc/passwd', `/etc/nsswitch.conf' and others. These
186 files must all contain correct and sensible content.
188 To format the `GNU C Library Reference Manual' for printing, type
189 `make dvi'. You need a working TeX installation to do this. The
190 distribution already includes the on-line formatted version of the
191 manual, as Info files. You can regenerate those with `make info', but
192 it shouldn't be necessary.
194 The library has a number of special-purpose configuration parameters
195 which you can find in `Makeconfig'. These can be overwritten with the
196 file `configparms'. To change them, create a `configparms' in your
197 build directory and add values as appropriate for your system. The
198 file is included and parsed by `make' and has to follow the conventions
201 It is easy to configure the GNU C library for cross-compilation by
202 setting a few variables in `configparms'. Set `CC' to the
203 cross-compiler for the target you configured the library for; it is
204 important to use this same `CC' value when running `configure', like
205 this: `CC=TARGET-gcc configure TARGET'. Set `BUILD_CC' to the compiler
206 to use for programs run on the build system as part of compiling the
207 library. You may need to set `AR' and `RANLIB' to cross-compiling
208 versions of `ar' and `ranlib' if the native tools are not configured to
209 work with object files for the target you configured for.
211 Installing the C Library
212 ========================
214 To install the library and its header files, and the Info files of the
215 manual, type `env LANGUAGE=C LC_ALL=C make install'. This will build
216 things, if necessary, before installing them; however, you should still
217 compile everything first. If you are installing glibc as your primary
218 C library, we recommend that you shut the system down to single-user
219 mode first, and reboot afterward. This minimizes the risk of breaking
220 things when the library changes out from underneath.
222 If you're upgrading from Linux libc5 or some other C library, you
223 need to replace the `/usr/include' with a fresh directory before
224 installing it. The new `/usr/include' should contain the Linux
225 headers, but nothing else.
227 You must first build the library (`make'), optionally check it
228 (`make check'), switch the include directories and then install (`make
229 install'). The steps must be done in this order. Not moving the
230 directory before install will result in an unusable mixture of header
231 files from both libraries, but configuring, building, and checking the
232 library requires the ability to compile and run programs against the old
235 If you are upgrading from a previous installation of glibc 2.0 or
236 2.1, `make install' will do the entire job. You do not need to remove
237 the old includes - if you want to do so anyway you must then follow the
240 You may also need to reconfigure GCC to work with the new library.
241 The easiest way to do that is to figure out the compiler switches to
242 make it work again (`-Wl,--dynamic-linker=/lib/ld-linux.so.2' should
243 work on GNU/Linux systems) and use them to recompile gcc. You can also
244 edit the specs file (`/usr/lib/gcc-lib/TARGET/VERSION/specs'), but that
245 is a bit of a black art.
247 You can install glibc somewhere other than where you configured it
248 to go by setting the `install_root' variable on the command line for
249 `make install'. The value of this variable is prepended to all the
250 paths for installation. This is useful when setting up a chroot
251 environment or preparing a binary distribution. The directory should be
252 specified with an absolute file name.
254 Glibc 2.2 includes a daemon called `nscd', which you may or may not
255 want to run. `nscd' caches name service lookups; it can dramatically
256 improve performance with NIS+, and may help with DNS as well.
258 One auxiliary program, `/usr/libexec/pt_chown', is installed setuid
259 `root'. This program is invoked by the `grantpt' function; it sets the
260 permissions on a pseudoterminal so it can be used by the calling
261 process. This means programs like `xterm' and `screen' do not have to
262 be setuid to get a pty. (There may be other reasons why they need
263 privileges.) If you are using a 2.1 or newer Linux kernel with the
264 `devptsfs' or `devfs' filesystems providing pty slaves, you don't need
265 this program; otherwise you do. The source for `pt_chown' is in
266 `login/programs/pt_chown.c'.
268 After installation you might want to configure the timezone and
269 locale installation of your system. The GNU C library comes with a
270 locale database which gets configured with `localedef'. For example, to
271 set up a German locale with name `de_DE', simply issue the command
272 `localedef -i de_DE -f ISO-8859-1 de_DE'. To configure all locales
273 that are supported by glibc, you can issue from your build directory the
274 command `make localedata/install-locales'.
276 To configure the locally used timezone, set the `TZ' environment
277 variable. The script `tzselect' helps you to select the right value.
278 As an example, for Germany, `tzselect' would tell you to use
279 `TZ='Europe/Berlin''. For a system wide installation (the given paths
280 are for an installation with `--prefix=/usr'), link the timezone file
281 which is in `/usr/share/zoneinfo' to the file `/etc/localtime'. For
282 Germany, you might execute `ln -s /usr/share/zoneinfo/Europe/Berlin
285 Recommended Tools for Compilation
286 =================================
288 We recommend installing the following GNU tools before attempting to
289 build the GNU C library:
291 * GNU `make' 3.79 or newer
293 You need the latest version of GNU `make'. Modifying the GNU C
294 Library to work with other `make' programs would be so difficult
295 that we recommend you port GNU `make' instead. *Really.* We
296 recommend GNU `make' version 3.79. All earlier versions have
297 severe bugs or lack features.
299 * GCC 3.4 or newer, GCC 4.1 recommended
301 The GNU C library can only be compiled with the GNU C compiler
302 family. For the 2.3 releases, GCC 3.2 or higher is required; GCC
303 3.4 is the compiler we advise to use for 2.3 versions. For the
304 2.4 release, GCC 3.4 or higher is required; as of this writing,
305 GCC 4.1 is the compiler we advise to use for current versions. On
306 certain machines including `powerpc64', compilers prior to GCC 4.0
307 have bugs that prevent them compiling the C library code in the
308 2.4 release. On other machines, GCC 4.1 is required to build the C
309 library with support for the correct `long double' type format;
310 these include `powerpc' (32 bit), `s390' and `s390x'.
312 You can use whatever compiler you like to compile programs that
313 use GNU libc, but be aware that both GCC 2.7 and 2.8 have bugs in
314 their floating-point support that may be triggered by the math
317 Check the FAQ for any special compiler issues on particular
322 You must use GNU `binutils' (as and ld) to build the GNU C library.
323 No other assembler or linker has the necessary functionality at the
324 moment. The configure scripts checks for the appropriate version
325 for the platform. Too-old versions will prevent building glibc.
327 * GNU `texinfo' 3.12f
329 To correctly translate and install the Texinfo documentation you
330 need this version of the `texinfo' package. Earlier versions do
331 not understand all the tags used in the document, and the
332 installation mechanism for the info files is not present or works
335 * GNU `awk' 3.0, or higher
337 `Awk' is used in several places to generate files. `gawk' 3.0 is
342 Perl is not required, but it is used if present to test the
343 installation. We may decide to use it elsewhere in the future.
345 * GNU `sed' 3.02 or newer
347 `Sed' is used in several places to generate files. Most scripts
348 work with any version of `sed'. The known exception is the script
349 `po2test.sed' in the `intl' subdirectory which is used to generate
350 `msgs.h' for the test suite. This script works correctly only
351 with GNU `sed' 3.02. If you like to run the test suite, you
352 should definitely upgrade `sed'.
355 If you change any of the `configure.in' files you will also need
357 * GNU `autoconf' 2.53 or higher
359 and if you change any of the message translation files you will need
361 * GNU `gettext' 0.10.36 or later
363 You may also need these packages if you upgrade your source tree using
364 patches, although we try to avoid this.
366 Specific advice for GNU/Linux systems
367 =====================================
369 If you are installing GNU libc on a GNU/Linux system, you need to have
370 the header files from a 2.2 or newer kernel around for reference. For
371 some architectures, like ia64, sh and hppa, you need at least headers
372 from kernel 2.3.99 (sh and hppa) or 2.4.0 (ia64). You do not need to
373 use that kernel, just have its headers where glibc can access at them.
374 The easiest way to do this is to unpack it in a directory such as
375 `/usr/src/linux-2.2.1'. In that directory, run `make config' and
376 accept all the defaults. Then run `make include/linux/version.h'.
377 Finally, configure glibc with the option
378 `--with-headers=/usr/src/linux-2.2.1/include'. Use the most recent
379 kernel you can get your hands on.
381 An alternate tactic is to unpack the 2.2 kernel and run `make
382 config' as above; then, rename or delete `/usr/include', create a new
383 `/usr/include', and make symbolic links of `/usr/include/linux' and
384 `/usr/include/asm' into the kernel sources. You can then configure
385 glibc with no special options. This tactic is recommended if you are
386 upgrading from libc5, since you need to get rid of the old header files
389 After installing GNU libc, you may need to remove or rename
390 `/usr/include/linux' and `/usr/include/asm', and replace them with
391 copies of `include/linux' and `include/asm-$ARCHITECTURE' taken from
392 the Linux source package which supplied kernel headers for building the
393 library. ARCHITECTURE will be the machine architecture for which the
394 library was built, such as `i386' or `alpha'. You do not need to do
395 this if you did not specify an alternate kernel header source using
396 `--with-headers'. The intent here is that these directories should be
397 copies of, *not* symlinks to, the kernel headers used to build the
400 Note that `/usr/include/net' and `/usr/include/scsi' should *not* be
401 symlinks into the kernel sources. GNU libc provides its own versions
404 GNU/Linux expects some components of the libc installation to be in
405 `/lib' and some in `/usr/lib'. This is handled automatically if you
406 configure glibc with `--prefix=/usr'. If you set some other prefix or
407 allow it to default to `/usr/local', then all the components are
410 If you are upgrading from libc5, you need to recompile every shared
411 library on your system against the new library for the sake of new code,
412 but keep the old libraries around for old binaries to use. This is
413 complicated and difficult. Consult the Glibc2 HOWTO at
414 `http://www.imaxx.net/~thrytis/glibc' for details.
416 You cannot use `nscd' with 2.0 kernels, due to bugs in the
417 kernel-side thread support. `nscd' happens to hit these bugs
418 particularly hard, but you might have problems with any threaded
424 There are probably bugs in the GNU C library. There are certainly
425 errors and omissions in this manual. If you report them, they will get
426 fixed. If you don't, no one will ever know about them and they will
427 remain unfixed for all eternity, if not longer.
429 It is a good idea to verify that the problem has not already been
430 reported. Bugs are documented in two places: The file `BUGS' describes
431 a number of well known bugs and the bug tracking system has a WWW
432 interface at `http://sources.redhat.com/bugzilla/'. The WWW interface
433 gives you access to open and closed reports. A closed report normally
434 includes a patch or a hint on solving the problem.
436 To report a bug, first you must find it. With any luck, this will
437 be the hard part. Once you've found a bug, make sure it's really a
438 bug. A good way to do this is to see if the GNU C library behaves the
439 same way some other C library does. If so, probably you are wrong and
440 the libraries are right (but not necessarily). If not, one of the
441 libraries is probably wrong. It might not be the GNU library. Many
442 historical Unix C libraries permit things that we don't, such as
443 closing a file twice.
445 If you think you have found some way in which the GNU C library does
446 not conform to the ISO and POSIX standards (*note Standards and
447 Portability::), that is definitely a bug. Report it!
449 Once you're sure you've found a bug, try to narrow it down to the
450 smallest test case that reproduces the problem. In the case of a C
451 library, you really only need to narrow it down to one library function
452 call, if possible. This should not be too difficult.
454 The final step when you have a simple test case is to report the bug.
455 Do this using the WWW interface to the bug database.
457 If you are not sure how a function should behave, and this manual
458 doesn't tell you, that's a bug in the manual. Report that too! If the
459 function's behavior disagrees with the manual, then either the library
460 or the manual has a bug, so report the disagreement. If you find any
461 errors or omissions in this manual, please report them to the bug
462 database. If you refer to specific sections of the manual, please
463 include the section names for easier identification.