1 Installing the GNU C Library
2 ****************************
4 Before you do anything else, you should read the file `FAQ' found 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 tarfiles 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. As of the
13 2.2 release, one important component of glibc is distributed as
14 "official" add-ons: the linuxthreads add-on. Unless you are doing an
15 unusual installation, you should get this.
17 Support for POSIX threads is maintained by someone else, so it's in a
18 separate package. It is only available for Linux systems, but this will
19 change in the future. Get it from the same place you got the main
20 bundle; the file is `glibc-linuxthreads-VERSION.tar.gz'.
22 You will need recent versions of several GNU tools: definitely GCC
23 and GNU Make, and possibly others. *Note Tools for Compilation::,
26 Configuring and compiling GNU Libc
27 ==================================
29 GNU libc can be compiled in the source directory, but we strongly
30 advise to build it in a separate build directory. For example, if you
31 have unpacked the glibc sources in `/src/gnu/glibc-2.2.0', create a
32 directory `/src/gnu/glibc-build' to put the object files in. This
33 allows removing the whole build directory in case an error occurs,
34 which is the safest way to get a fresh start and should always be done.
36 From your object directory, run the shell script `configure' found
37 at the top level of the source tree. In the scenario above, you'd type
39 $ ../glibc-2.2.0/configure ARGS...
41 Please note that even if you're building in a separate build
42 directory, the compilation needs to modify a few files in the source
43 directory, especially some files in the manual subdirectory.
45 `configure' takes many options, but you can get away with knowing only
46 two: `--prefix' and `--enable-add-ons'. The `--prefix' option tells
47 configure where you want glibc installed. This defaults to
48 `/usr/local'. The `--enable-add-ons' option tells configure to use all
49 the add-on bundles it finds in the source directory. Since important
50 functionality is provided in add-ons, you should always specify this
53 It may also be useful to set the CC and CFLAGS variables in the
54 environment when running `configure'. CC selects the C compiler that
55 will be used, and CFLAGS sets optimization options for the compiler.
57 The following list describes all of the available options for
61 Install machine-independent data files in subdirectories of
62 `DIRECTORY'. The default is to install in `/usr/local'.
64 `--exec-prefix=DIRECTORY'
65 Install the library and other machine-dependent files in
66 subdirectories of `DIRECTORY'. The default is to the `--prefix'
67 directory if that option is specified, or `/usr/local' otherwise.
69 `--with-headers=DIRECTORY'
70 Look for kernel header files in DIRECTORY, not `/usr/include'.
71 Glibc needs information from the kernel's private header files.
72 It will normally look in `/usr/include' for them, but if you
73 specify this option, it will look in DIRECTORY instead.
75 This option is primarily of use on a system where the headers in
76 `/usr/include' come from an older version of glibc. Conflicts can
77 occasionally happen in this case. Note that Linux libc5 qualifies
78 as an older version of glibc. You can also use this option if you
79 want to compile glibc with a newer set of kernel headers than the
80 ones found in `/usr/include'.
82 `--enable-add-ons[=LIST]'
83 Enable add-on packages in your source tree. If this option is
84 specified with no list, it enables all the add-on packages it
85 finds. If you do not wish to use some add-on package that you
86 have present in your source tree, give this option a list of the
87 add-ons that you _do_ want used, like this:
88 `--enable-add-ons=linuxthreads'
90 `--enable-kernel=VERSION'
91 This option is currently only useful on Linux systems. The
92 VERSION parameter should have the form X.Y.Z and describes the
93 smallest version of the Linux kernel the generated library is
94 expected to support. The higher the VERSION number is, the less
95 compatibility code is added, and the faster the code gets.
97 `--with-binutils=DIRECTORY'
98 Use the binutils (assembler and linker) in `DIRECTORY', not the
99 ones the C compiler would default to. You could use this option if
100 the default binutils on your system cannot deal with all the
101 constructs in the GNU C library. In that case, `configure' will
102 detect the problem and suppress these constructs, so that the
103 library will still be usable, but functionality may be lost--for
104 example, you can't build a shared libc with old binutils.
107 Use this option if your computer lacks hardware floating-point
108 support and your operating system does not emulate an FPU.
111 Don't build shared libraries even if it is possible. Not all
112 systems support shared libraries; you need ELF support and
113 (currently) the GNU linker.
116 Don't build libraries with profiling information. You may want to
117 use this option if you don't plan to do profiling.
120 Use maximum optimization for the normal (static and shared)
121 libraries, and compile separate static libraries with debugging
122 information and no optimization. We recommend against this. The
123 extra optimization doesn't gain you much, it may provoke compiler
124 bugs, and you won't be able to trace bugs through the C library.
126 `--disable-versioning'
127 Don't compile the shared libraries with symbol version information.
128 Doing this will make the resulting library incompatible with old
129 binaries, so it's not recommended.
131 `--enable-static-nss'
132 Compile static versions of the NSS (Name Service Switch) libraries.
133 This is not recommended because it defeats the purpose of NSS; a
134 program linked statically with the NSS libraries cannot be
135 dynamically reconfigured to use a different name database.
138 By default the C library is build with support for thread-local
139 storage if the used tools support it. By using `--without-tls'
140 this can be prevented though there generally is no reason since it
141 creates compatibility problems.
143 `--build=BUILD-SYSTEM'
145 These options are for cross-compiling. If you specify both
146 options and BUILD-SYSTEM is different from HOST-SYSTEM, `configure'
147 will prepare to cross-compile glibc from BUILD-SYSTEM to be used
148 on HOST-SYSTEM. You'll probably need the `--with-headers' option
149 too, and you may have to override CONFIGURE's selection of the
150 compiler and/or binutils.
152 If you only specify `--host', configure will prepare for a native
153 compile but use what you specify instead of guessing what your
154 system is. This is most useful to change the CPU submodel. For
155 example, if configure guesses your machine as `i586-pc-linux-gnu'
156 but you want to compile a library for 386es, give
157 `--host=i386-pc-linux-gnu' or just `--host=i386-linux' and add the
158 appropriate compiler flags (`-mcpu=i386' will do the trick) to
161 If you specify just `--build', configure will get confused.
163 To build the library and related programs, type `make'. This will
164 produce a lot of output, some of which may look like errors from `make'
165 but isn't. Look for error messages from `make' containing `***'.
166 Those indicate that something is really wrong.
168 The compilation process can take several hours. Expect at least two
169 hours for the default configuration on i586 for Linux. For Hurd times
170 are much longer. Except for EGCS 1.1 and GCC 2.95 (and later versions
171 of GCC), all supported versions of GCC have a problem which causes them
172 to take several minutes to compile certain files in the iconvdata
173 directory. Do not panic if the compiler appears to hang.
175 If you want to run a parallel make, simply pass the `-j' option with
176 an appropriate numeric parameter to `make'. You need a recent GNU
177 `make' version, though.
179 To build and run test programs which exercise some of the library
180 facilities, type `make check'. If it does not complete successfully,
181 do not use the built library, and report a bug after verifying that the
182 problem is not already known. *Note Reporting Bugs::, for instructions
183 on reporting bugs. Note that some of the tests assume they are not
184 being run by `root'. We recommend you compile and test glibc as an
187 Before reporting bugs make sure there is no problem with your system.
188 The tests (and later installation) uses some pre-existing files of the
189 system such as `/etc/passwd', `/etc/nsswitch.conf' and others. These
190 files must all contain correct and sensible content.
192 To format the `GNU C Library Reference Manual' for printing, type
193 `make dvi'. You need a working TeX installation to do this. The
194 distribution already includes the on-line formatted version of the
195 manual, as Info files. You can regenerate those with `make info', but
196 it shouldn't be necessary.
198 The library has a number of special-purpose configuration parameters
199 which you can find in `Makeconfig'. These can be overwritten with the
200 file `configparms'. To change them, create a `configparms' in your
201 build directory and add values as appropriate for your system. The
202 file is included and parsed by `make' and has to follow the conventions
205 It is easy to configure the GNU C library for cross-compilation by
206 setting a few variables in `configparms'. Set `CC' to the
207 cross-compiler for the target you configured the library for; it is
208 important to use this same `CC' value when running `configure', like
209 this: `CC=TARGET-gcc configure TARGET'. Set `BUILD_CC' to the compiler
210 to use for for programs run on the build system as part of compiling
211 the library. You may need to set `AR' and `RANLIB' to cross-compiling
212 versions of `ar' and `ranlib' if the native tools are not configured to
213 work with object files for the target you configured for.
215 Installing the C Library
216 ========================
218 To install the library and its header files, and the Info files of
219 the manual, type `env LANGUAGE=C LC_ALL=C make install'. This will
220 build things if necessary, before installing them. However, you should
221 still compile everything first. If you are installing glibc as your
222 primary C library, we recommend that you shut the system down to
223 single-user mode first, and reboot afterward. This minimizes the risk
224 of breaking things when the library changes out from underneath.
226 If you're upgrading from Linux libc5 or some other C library, you
227 need to replace the `/usr/include' with a fresh directory before
228 installing it. The new `/usr/include' should contain the Linux
229 headers, but nothing else.
231 You must first build the library (`make'), optionally check it
232 (`make check'), switch the include directories and then install (`make
233 install'). The steps must be done in this order. Not moving the
234 directory before install will result in an unusable mixture of header
235 files from both libraries, but configuring, building, and checking the
236 library requires the ability to compile and run programs against the old
239 If you are upgrading from a previous installation of glibc 2.0 or
240 2.1, `make install' will do the entire job. You do not need to remove
241 the old includes - if you want to do so anyway you must then follow the
244 You may also need to reconfigure GCC to work with the new library.
245 The easiest way to do that is to figure out the compiler switches to
246 make it work again (`-Wl,--dynamic-linker=/lib/ld-linux.so.2' should
247 work on Linux systems) and use them to recompile gcc. You can also
248 edit the specs file (`/usr/lib/gcc-lib/TARGET/VERSION/specs'), but that
249 is a bit of a black art.
251 You can install glibc somewhere other than where you configured it
252 to go by setting the `install_root' variable on the command line for
253 `make install'. The value of this variable is prepended to all the
254 paths for installation. This is useful when setting up a chroot
255 environment or preparing a binary distribution. The directory should be
256 specified with an absolute file name.
258 Glibc 2.2 includes a daemon called `nscd', which you may or may not
259 want to run. `nscd' caches name service lookups; it can dramatically
260 improve performance with NIS+, and may help with DNS as well.
262 One auxiliary program, `/usr/libexec/pt_chown', is installed setuid
263 `root'. This program is invoked by the `grantpt' function; it sets the
264 permissions on a pseudoterminal so it can be used by the calling
265 process. This means programs like `xterm' and `screen' do not have to
266 be setuid to get a pty. (There may be other reasons why they need
267 privileges.) If you are using a 2.1 or newer Linux kernel with the
268 `devptsfs' or `devfs' filesystems providing pty slaves, you don't need
269 this program; otherwise you do. The source for `pt_chown' is in
270 `login/programs/pt_chown.c'.
272 After installation you might want to configure the timezone and
273 locale installation of your system. The GNU C library comes with a
274 locale database which gets configured with `localedef'. For example, to
275 set up a German locale with name `de_DE', simply issue the command
276 `localedef -i de_DE -f ISO-8859-1 de_DE'. To configure all locales
277 that are supported by glibc, you can issue from your build directory the
278 command `make localedata/install-locales'.
280 To configure the locally used timezone, you can either set the `TZ'
281 environment variable. The script `tzselect' helps you to select the
282 right value. As an example for Germany, tzselect would tell you to use
283 `TZ='Europe/Berlin''. For a system wide installation (the given paths
284 are for an installation with `--prefix=/usr'), link the timezone file
285 which is in `/usr/share/zoneinfo' to the file `/etc/localtime'. For
286 Germany, you might execute `ln -s /usr/share/zoneinfo/Europe/Berlin
289 Recommended Tools for Compilation
290 =================================
292 We recommend installing the following GNU tools before attempting to
293 build the GNU C library:
295 * GNU `make' 3.79 or newer
297 You need the latest version of GNU `make'. Modifying the GNU C
298 Library to work with other `make' programs would be so difficult
299 that we recommend you port GNU `make' instead. *Really.* We
300 recommend version GNU `make' version 3.79. All earlier versions
301 have severe bugs or lack features.
305 The GNU C library can only be compiled with the GNU C compiler
306 family. As of the 2.2 release, GCC 2.95.2 or higher is required.
307 As of this writing, GCC 2.95.3 is the compiler we advise to use.
309 You can use whatever compiler you like to compile programs that
310 use GNU libc, but be aware that both GCC 2.7 and 2.8 have bugs in
311 their floating-point support that may be triggered by the math
314 For PPC you might need some patches even on top of the last GCC
315 version. See the FAQ.
317 * GNU `binutils' 2.10.1 or later
319 You must use GNU binutils (as and ld) if you want to build a shared
320 library. Even if you don't, we recommend you use them anyway. No
321 one has tested compilation with non-GNU binutils in a long time.
323 The quality of binutils releases has varied a bit recently. The
324 bugs are in obscure features, but glibc uses quite a few of those.
325 2.10.1 and later releases are known to work. Versions after
326 2.8.1.0.23 may or may not work. Older versions definitely don't.
328 For PPC you might need some patches even on top of the last
329 binutils version. See the FAQ.
331 * GNU `texinfo' 3.12f
333 To correctly translate and install the Texinfo documentation you
334 need this version of the `texinfo' package. Earlier versions do
335 not understand all the tags used in the document, and the
336 installation mechanism for the info files is not present or works
339 * GNU `awk' 3.0, or some other POSIX awk
341 Awk is used in several places to generate files. The scripts
342 should work with any POSIX-compliant awk implementation; `gawk'
343 3.0 and `mawk' 1.3 are known to work.
347 Perl is not required, but it is used if present to test the
348 installation. We may decide to use it elsewhere in the future.
350 * GNU `sed' 3.02 or newer
352 Sed is used in several places to generate files. Most scripts
353 work with any version of `sed'. The known exception is the script
354 `po2test.sed' in the `intl' subdirectory which is used to generate
355 `msgs.h' for the testsuite. This script works correctly only with
356 GNU `sed' 3.02. If you like to run the testsuite, you should
357 definitely upgrade `sed'.
360 If you change any of the `configure.in' files you will also need
362 * GNU `autoconf' 2.12 or higher
364 and if you change any of the message translation files you will need
366 * GNU `gettext' 0.10.36 or later
368 You may also need these packages if you upgrade your source tree using
369 patches, although we try to avoid this.
371 Supported Configurations
372 ========================
374 The GNU C Library currently supports configurations that match the
392 Former releases of this library (version 2.1 and/or 2.0) used to run
393 on the following configurations:
398 Very early releases (version 1.09.1 and perhaps earlier versions)
399 used to run on the following configurations:
410 iX86-force_cpu386-none
424 Since no one has volunteered to test and fix these configurations,
425 they are not supported at the moment. They probably don't compile;
426 they definitely don't work anymore. Porting the library is not hard.
427 If you are interested in doing a port, please contact the glibc
428 maintainers by sending electronic mail to <bug-glibc@gnu.org>.
430 Valid cases of `iX86' include `i386', `i486', `i586', and `i686'.
431 All of those configurations produce a library that can run on this
432 processor and newer processors. The GCC compiler by default generates
433 code that's optimized for the machine it's configured for and will use
434 the instructions available on that machine. For example if your GCC is
435 configured for `i686', gcc will optimize for `i686' and might issue
436 some `i686' specific instructions. To generate code for other models,
437 you have to configure for that model and give GCC the appropriate
438 `-march=' and `-mcpu=' compiler switches via CFLAGS.
440 Specific advice for Linux systems
441 =================================
443 If you are installing GNU libc on a Linux system, you need to have
444 the header files from a 2.2 or newer kernel around for reference. For
445 some architectures, like ia64, sh and hppa, you need at least headers
446 from kernel 2.3.99 (sh and hppa) or 2.4.0 (ia64). You do not need to
447 use that kernel, just have its headers where glibc can access at them.
448 The easiest way to do this is to unpack it in a directory such as
449 `/usr/src/linux-2.2.1'. In that directory, run `make config' and
450 accept all the defaults. Then run `make include/linux/version.h'.
451 Finally, configure glibc with the option
452 `--with-headers=/usr/src/linux-2.2.1/include'. Use the most recent
453 kernel you can get your hands on.
455 An alternate tactic is to unpack the 2.2 kernel and run `make
456 config' as above. Then rename or delete `/usr/include', create a new
457 `/usr/include', and make the usual symbolic links of
458 `/usr/include/linux' and `/usr/include/asm' into the 2.2 kernel
459 sources. You can then configure glibc with no special options. This
460 tactic is recommended if you are upgrading from libc5, since you need
461 to get rid of the old header files anyway.
463 Note that `/usr/include/net' and `/usr/include/scsi' should *not* be
464 symlinks into the kernel sources. GNU libc provides its own versions
467 Linux expects some components of the libc installation to be in
468 `/lib' and some in `/usr/lib'. This is handled automatically if you
469 configure glibc with `--prefix=/usr'. If you set some other prefix or
470 allow it to default to `/usr/local', then all the components are
473 If you are upgrading from libc5, you need to recompile every shared
474 library on your system against the new library for the sake of new code,
475 but keep the old libraries around for old binaries to use. This is
476 complicated and difficult. Consult the Glibc2 HOWTO at
477 <http://www.imaxx.net/~thrytis/glibc> for details.
479 You cannot use `nscd' with 2.0 kernels, due to bugs in the
480 kernel-side thread support. `nscd' happens to hit these bugs
481 particularly hard, but you might have problems with any threaded
487 There are probably bugs in the GNU C library. There are certainly
488 errors and omissions in this manual. If you report them, they will get
489 fixed. If you don't, no one will ever know about them and they will
490 remain unfixed for all eternity, if not longer.
492 It is a good idea to verify that the problem has not already been
493 reported. Bugs are documented in two places: The file `BUGS' describes
494 a number of well known bugs and the bug tracking system has a WWW
495 interface at <http://www-gnats.gnu.org:8080/cgi-bin/wwwgnats.pl>. The
496 WWW interface gives you access to open and closed reports. The closed
497 reports normally include a patch or a hint on solving the problem.
499 To report a bug, first you must find it. Hopefully, this will be the
500 hard part. Once you've found a bug, make sure it's really a bug. A
501 good way to do this is to see if the GNU C library behaves the same way
502 some other C library does. If so, probably you are wrong and the
503 libraries are right (but not necessarily). If not, one of the libraries
504 is probably wrong. It might not be the GNU library. Many historical
505 Unix C libraries permit things that we don't, such as closing a file
508 If you think you have found some way in which the GNU C library does
509 not conform to the ISO and POSIX standards (*note Standards and
510 Portability::), that is definitely a bug. Report it!
512 Once you're sure you've found a bug, try to narrow it down to the
513 smallest test case that reproduces the problem. In the case of a C
514 library, you really only need to narrow it down to one library function
515 call, if possible. This should not be too difficult.
517 The final step when you have a simple test case is to report the bug.
518 Do this using the `glibcbug' script. It is installed with libc, or if
519 you haven't installed it, will be in your build directory. Send your
520 test case, the results you got, the results you expected, and what you
521 think the problem might be (if you've thought of anything). `glibcbug'
522 will insert the configuration information we need to see, and ship the
523 report off to <bugs@gnu.org>. Don't send a message there directly; it
524 is fed to a program that expects mail to be formatted in a particular
527 If you are not sure how a function should behave, and this manual
528 doesn't tell you, that's a bug in the manual. Report that too! If the
529 function's behavior disagrees with the manual, then either the library
530 or the manual has a bug, so report the disagreement. If you find any
531 errors or omissions in this manual, please report them to the Internet
532 address <bug-glibc-manual@gnu.org>. If you refer to specific sections
533 of the manual, please include the section names for easier