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-VERSION', 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-VERSION/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 header files describing
63 the interface to the kernel. Glibc will normally look in
64 `/usr/include' for them, but if you specify this option, it will
65 look in DIRECTORY instead.
67 This option is primarily of use on a system where the headers in
68 `/usr/include' come from an older version of glibc. Conflicts can
69 occasionally happen in this case. You can also use this option if
70 you want to compile glibc with a newer set of kernel headers than
71 the 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-VERSION'.
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.
106 Don't build shared libraries even if it is possible. Not all
107 systems support shared libraries; you need ELF support and
108 (currently) the GNU linker.
111 Don't build libraries with profiling information. You may want to
112 use this option if you don't plan to do profiling.
114 `--disable-versioning'
115 Don't compile the shared libraries with symbol version information.
116 Doing this will make the resulting library incompatible with old
117 binaries, so it's not recommended.
119 `--enable-static-nss'
120 Compile static versions of the NSS (Name Service Switch) libraries.
121 This is not recommended because it defeats the purpose of NSS; a
122 program linked statically with the NSS libraries cannot be
123 dynamically reconfigured to use a different name database.
126 By default the C library is built with support for thread-local
127 storage if the used tools support it. By using `--without-tls'
128 this can be prevented though there generally is no reason since it
129 creates compatibility problems.
131 `--build=BUILD-SYSTEM'
133 These options are for cross-compiling. If you specify both
134 options and BUILD-SYSTEM is different from HOST-SYSTEM, `configure'
135 will prepare to cross-compile glibc from BUILD-SYSTEM to be used
136 on HOST-SYSTEM. You'll probably need the `--with-headers' option
137 too, and you may have to override CONFIGURE's selection of the
138 compiler and/or binutils.
140 If you only specify `--host', `configure' will prepare for a
141 native compile but use what you specify instead of guessing what
142 your system is. This is most useful to change the CPU submodel.
143 For example, if `configure' guesses your machine as
144 `i586-pc-linux-gnu' but you want to compile a library for 386es,
145 give `--host=i386-pc-linux-gnu' or just `--host=i386-linux' and add
146 the appropriate compiler flags (`-mcpu=i386' will do the trick) to
149 If you specify just `--build', `configure' will get confused.
151 To build the library and related programs, type `make'. This will
152 produce a lot of output, some of which may look like errors from `make'
153 but isn't. Look for error messages from `make' containing `***'.
154 Those indicate that something is seriously wrong.
156 The compilation process can take a long time, depending on the
157 configuration and the speed of your machine. Some complex modules may
158 take a very long time to compile, as much as several minutes on slower
159 machines. Do not panic if the compiler appears to hang.
161 If you want to run a parallel make, simply pass the `-j' option with
162 an appropriate numeric parameter to `make'. You need a recent GNU
163 `make' version, though.
165 To build and run test programs which exercise some of the library
166 facilities, type `make check'. If it does not complete successfully,
167 do not use the built library, and report a bug after verifying that the
168 problem is not already known. *Note Reporting Bugs::, for instructions
169 on reporting bugs. Note that some of the tests assume they are not
170 being run by `root'. We recommend you compile and test glibc as an
173 Before reporting bugs make sure there is no problem with your system.
174 The tests (and later installation) use some pre-existing files of the
175 system such as `/etc/passwd', `/etc/nsswitch.conf' and others. These
176 files must all contain correct and sensible content.
178 To format the `GNU C Library Reference Manual' for printing, type
179 `make dvi'. You need a working TeX installation to do this. The
180 distribution already includes the on-line formatted version of the
181 manual, as Info files. You can regenerate those with `make info', but
182 it shouldn't be necessary.
184 The library has a number of special-purpose configuration parameters
185 which you can find in `Makeconfig'. These can be overwritten with the
186 file `configparms'. To change them, create a `configparms' in your
187 build directory and add values as appropriate for your system. The
188 file is included and parsed by `make' and has to follow the conventions
191 It is easy to configure the GNU C library for cross-compilation by
192 setting a few variables in `configparms'. Set `CC' to the
193 cross-compiler for the target you configured the library for; it is
194 important to use this same `CC' value when running `configure', like
195 this: `CC=TARGET-gcc configure TARGET'. Set `BUILD_CC' to the compiler
196 to use for programs run on the build system as part of compiling the
197 library. You may need to set `AR' to cross-compiling versions of `ar'
198 if the native tools are not configured to work with object files for
199 the target you configured for.
201 Installing the C Library
202 ========================
204 To install the library and its header files, and the Info files of the
205 manual, type `env LANGUAGE=C LC_ALL=C make install'. This will build
206 things, if necessary, before installing them; however, you should still
207 compile everything first. If you are installing glibc as your primary
208 C library, we recommend that you shut the system down to single-user
209 mode first, and reboot afterward. This minimizes the risk of breaking
210 things when the library changes out from underneath.
212 `make install' will do the entire job of upgrading from a previous
213 installation of glibc 2.x. There may sometimes be headers left behind
214 from the previous installation, but those are generally harmless. If
215 you want to avoid leaving headers behind you can do things in the
218 You must first build the library (`make'), optionally check it
219 (`make check'), switch the include directories and then install (`make
220 install'). The steps must be done in this order. Not moving the
221 directory before install will result in an unusable mixture of header
222 files from both libraries, but configuring, building, and checking the
223 library requires the ability to compile and run programs against the old
224 library. The new `/usr/include', after switching the include
225 directories and before installing the library should contain the Linux
226 headers, but nothing else. If you do this, you will need to restore
227 any headers from non-glibc libraries youself after installing the
230 You can install glibc somewhere other than where you configured it
231 to go by setting the `install_root' variable on the command line for
232 `make install'. The value of this variable is prepended to all the
233 paths for installation. This is useful when setting up a chroot
234 environment or preparing a binary distribution. The directory should be
235 specified with an absolute file name.
237 Glibc includes a daemon called `nscd', which you may or may not want
238 to run. `nscd' caches name service lookups; it can dramatically
239 improve performance with NIS+, and may help with DNS as well.
241 One auxiliary program, `/usr/libexec/pt_chown', is installed setuid
242 `root'. This program is invoked by the `grantpt' function; it sets the
243 permissions on a pseudoterminal so it can be used by the calling
244 process. This means programs like `xterm' and `screen' do not have to
245 be setuid to get a pty. (There may be other reasons why they need
246 privileges.) If you are using a 2.1 or newer Linux kernel with the
247 `devptsfs' or `devfs' filesystems providing pty slaves, you don't need
248 this program; otherwise you do. The source for `pt_chown' is in
249 `login/programs/pt_chown.c'.
251 After installation you might want to configure the timezone and
252 locale installation of your system. The GNU C library comes with a
253 locale database which gets configured with `localedef'. For example, to
254 set up a German locale with name `de_DE', simply issue the command
255 `localedef -i de_DE -f ISO-8859-1 de_DE'. To configure all locales
256 that are supported by glibc, you can issue from your build directory the
257 command `make localedata/install-locales'.
259 To configure the locally used timezone, set the `TZ' environment
260 variable. The script `tzselect' helps you to select the right value.
261 As an example, for Germany, `tzselect' would tell you to use
262 `TZ='Europe/Berlin''. For a system wide installation (the given paths
263 are for an installation with `--prefix=/usr'), link the timezone file
264 which is in `/usr/share/zoneinfo' to the file `/etc/localtime'. For
265 Germany, you might execute `ln -s /usr/share/zoneinfo/Europe/Berlin
268 Recommended Tools for Compilation
269 =================================
271 We recommend installing the following GNU tools before attempting to
272 build the GNU C library:
274 * GNU `make' 3.79 or newer
276 You need the latest version of GNU `make'. Modifying the GNU C
277 Library to work with other `make' programs would be so difficult
278 that we recommend you port GNU `make' instead. *Really.* We
279 recommend GNU `make' version 3.79. All earlier versions have
280 severe bugs or lack features.
282 * GCC 3.4 or newer, GCC 4.1 recommended
284 GCC 3.4 or higher is required; as of this writing, GCC 4.4 is the
285 compiler we advise to use for current versions. On certain
286 machines including `powerpc64', compilers prior to GCC 4.0 have
287 bugs that prevent them compiling the C library code. On other
288 machines, GCC 4.1 is required to build the C library with support
289 for the correct `long double' type format; these include `powerpc'
290 (32 bit), `s390' and `s390x'. For other architectures special
291 compiler-provided headers are needed (like `cpuid.h' on x86) which
292 only come with later compiler versions.
294 You can use whatever compiler you like to compile programs that
295 use GNU libc, but be aware that both GCC 2.7 and 2.8 have bugs in
296 their floating-point support that may be triggered by the math
299 Check the FAQ for any special compiler issues on particular
302 * GNU `binutils' 2.15 or later
304 You must use GNU `binutils' (as and ld) to build the GNU C library.
305 No other assembler or linker has the necessary functionality at the
308 * GNU `texinfo' 3.12f
310 To correctly translate and install the Texinfo documentation you
311 need this version of the `texinfo' package. Earlier versions do
312 not understand all the tags used in the document, and the
313 installation mechanism for the info files is not present or works
316 * GNU `awk' 3.0, or higher
318 `Awk' is used in several places to generate files. `gawk' 3.0 is
323 Perl is not required, but it is used if present to test the
324 installation. We may decide to use it elsewhere in the future.
326 * GNU `sed' 3.02 or newer
328 `Sed' is used in several places to generate files. Most scripts
329 work with any version of `sed'. The known exception is the script
330 `po2test.sed' in the `intl' subdirectory which is used to generate
331 `msgs.h' for the test suite. This script works correctly only
332 with GNU `sed' 3.02. If you like to run the test suite, you
333 should definitely upgrade `sed'.
336 If you change any of the `configure.in' files you will also need
338 * GNU `autoconf' 2.53 or higher
340 and if you change any of the message translation files you will need
342 * GNU `gettext' 0.10.36 or later
344 You may also need these packages if you upgrade your source tree using
345 patches, although we try to avoid this.
347 Specific advice for GNU/Linux systems
348 =====================================
350 If you are installing GNU libc on a GNU/Linux system, you need to have
351 the header files from a 2.6.19.1 or newer kernel around for reference.
352 These headers must be installed using `make headers_install'; the
353 headers present in the kernel source directory are not suitable for
354 direct use by GNU libc. You do not need to use that kernel, just have
355 its headers installed where glibc can access them, referred to here as
356 INSTALL-DIRECTORY. The easiest way to do this is to unpack it in a
357 directory such as `/usr/src/linux-VERSION'. In that directory, run
358 `make headers_install INSTALL_HDR_PATH=INSTALL-DIRECTORY'. Finally,
359 configure glibc with the option
360 `--with-headers=INSTALL-DIRECTORY/include'. Use the most recent kernel
361 you can get your hands on. (If you are cross-compiling GNU libc, you
362 need to specify `ARCH=ARCHITECTURE' in the `make headers_install'
363 command, where ARCHITECTURE is the architecture name used by the Linux
364 kernel, such as `x86' or `powerpc'.)
366 After installing GNU libc, you may need to remove or rename
367 directories such as `/usr/include/linux' and `/usr/include/asm', and
368 replace them with copies of directories such as `linux' and `asm' from
369 `INSTALL-DIRECTORY/include'. All directories present in
370 `INSTALL-DIRECTORY/include' should be copied, except that GNU libc
371 provides its own version of `/usr/include/scsi'; the files provided by
372 the kernel should be copied without replacing those provided by GNU
373 libc. The `linux', `asm' and `asm-generic' directories are required to
374 compile programs using GNU libc; the other directories describe
375 interfaces to the kernel but are not required if not compiling programs
376 using those interfaces. You do not need to copy kernel headers if you
377 did not specify an alternate kernel header source using
380 GNU/Linux expects some components of the libc installation to be in
381 `/lib' and some in `/usr/lib'. This is handled automatically if you
382 configure glibc with `--prefix=/usr'. If you set some other prefix or
383 allow it to default to `/usr/local', then all the components are
386 You cannot use `nscd' with 2.0 kernels, due to bugs in the
387 kernel-side thread support. `nscd' happens to hit these bugs
388 particularly hard, but you might have problems with any threaded
394 There are probably bugs in the GNU C library. There are certainly
395 errors and omissions in this manual. If you report them, they will get
396 fixed. If you don't, no one will ever know about them and they will
397 remain unfixed for all eternity, if not longer.
399 It is a good idea to verify that the problem has not already been
400 reported. Bugs are documented in two places: The file `BUGS' describes
401 a number of well known bugs and the bug tracking system has a WWW
402 interface at `http://sources.redhat.com/bugzilla/'. The WWW interface
403 gives you access to open and closed reports. A closed report normally
404 includes a patch or a hint on solving the problem.
406 To report a bug, first you must find it. With any luck, this will
407 be the hard part. Once you've found a bug, make sure it's really a
408 bug. A good way to do this is to see if the GNU C library behaves the
409 same way some other C library does. If so, probably you are wrong and
410 the libraries are right (but not necessarily). If not, one of the
411 libraries is probably wrong. It might not be the GNU library. Many
412 historical Unix C libraries permit things that we don't, such as
413 closing a file twice.
415 If you think you have found some way in which the GNU C library does
416 not conform to the ISO and POSIX standards (*note Standards and
417 Portability::), that is definitely a bug. Report it!
419 Once you're sure you've found a bug, try to narrow it down to the
420 smallest test case that reproduces the problem. In the case of a C
421 library, you really only need to narrow it down to one library function
422 call, if possible. This should not be too difficult.
424 The final step when you have a simple test case is to report the bug.
425 Do this using the WWW interface to the bug database.
427 If you are not sure how a function should behave, and this manual
428 doesn't tell you, that's a bug in the manual. Report that too! If the
429 function's behavior disagrees with the manual, then either the library
430 or the manual has a bug, so report the disagreement. If you find any
431 errors or omissions in this manual, please report them to the bug
432 database. If you refer to specific sections of the manual, please
433 include the section names for easier identification.
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