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 2.1 release, two important components of glibc are distributed as
14 "official" add-ons. Unless you are doing an unusual installation, you
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'. Support for
21 the `crypt' function is distributed separately because of United States
22 export restrictions. If you are outside the US or Canada, you must get
23 `crypt' support from a site outside the US, such as `ftp.gwdg.de'.
24 `ftp.gwdg.de' has the crypt distribution in `pub/linux/glibc'. (Most
25 non-US mirrors of `ftp.gnu.org' will have it too.) The file you need
26 is `glibc-crypt-VERSION.tar.gz'.
28 You will need recent versions of several GNU tools: definitely GCC
29 and GNU Make, and possibly others. *Note Tools for Compilation::,
32 Configuring and compiling GNU Libc
33 ==================================
35 GNU libc can be compiled in the source directory, but we strongly
36 advise to build it in a separate build directory. For example, if you
37 have unpacked the glibc sources in `/src/gnu/glibc-2.1.0', create a
38 directory `/src/gnu/glibc-build' to put the object files in. This
39 allows removing the whole build directory in case an error occurs,
40 which is the safest way to get a fresh start and should always be done.
42 From your object directory, run the shell script `configure' found
43 at the top level of the source tree. In the scenario above, you'd type
45 $ ../glibc-2.1.0/configure ARGS...
47 Please note that even if you're building in a separate build
48 directory, the compilation needs to modify a few files in the source
49 directory, especially some files in the manual subdirectory.
51 `configure' takes many options, but you can get away with knowing only
52 two: `--prefix' and `--enable-add-ons'. The `--prefix' option tells
53 configure where you want glibc installed. This defaults to
54 `/usr/local'. The `--enable-add-ons' option tells configure to use all
55 the add-on bundles it finds in the source directory. Since important
56 functionality is provided in add-ons, you should always specify this
59 It may also be useful to set the CC and CFLAGS variables in the
60 environment when running `configure'. CC selects the C compiler that
61 will be used, and CFLAGS sets optimization options for the compiler.
63 The following list describes all of the available options for
67 Install machine-independent data files in subdirectories of
68 `DIRECTORY'. The default is to install in `/usr/local'.
70 `--exec-prefix=DIRECTORY'
71 Install the library and other machine-dependent files in
72 subdirectories of `DIRECTORY'. The default is to the `--prefix'
73 directory if that option is specified, or `/usr/local' otherwise.
75 `--with-headers=DIRECTORY'
76 Look for kernel header files in DIRECTORY, not `/usr/include'.
77 Glibc needs information from the kernel's private header files.
78 It will normally look in `/usr/include' for them, but if you
79 specify this option, it will look in DIRECTORY instead.
81 This option is primarily of use on a system where the headers in
82 `/usr/include' come from an older version of glibc. Conflicts can
83 occasionally happen in this case. Note that Linux libc5 qualifies
84 as an older version of glibc. You can also use this option if you
85 want to compile glibc with a newer set of kernel headers than the
86 ones found in `/usr/include'.
88 `--enable-add-ons[=LIST]'
89 Enable add-on packages in your source tree. If this option is
90 specified with no list, it enables all the add-on packages it
91 finds. If you do not wish to use some add-on package that you
92 have present in your source tree, give this option a list of the
93 add-ons that you _do_ want used, like this:
94 `--enable-add-ons=crypt,linuxthreads'
96 `--with-binutils=DIRECTORY'
97 Use the binutils (assembler and linker) in `DIRECTORY', not the
98 ones the C compiler would default to. You could use this option if
99 the default binutils on your system cannot deal with all the
100 constructs in the GNU C library. In that case, `configure' will
101 detect the problem and suppress these constructs, so that the
102 library will still be usable, but functionality may be lost--for
103 example, you can't build a shared libc with old binutils.
106 Use this option if your computer lacks hardware floating-point
107 support and your operating system does not emulate an FPU.
110 Don't build shared libraries even if it is possible. Not all
111 systems support shared libraries; you need ELF support and
112 (currently) the GNU linker.
115 Don't build libraries with profiling information. You may want to
116 use this option if you don't plan to do profiling.
119 Use maximum optimization for the normal (static and shared)
120 libraries, and compile separate static libraries with debugging
121 information and no optimisation. We recommend against this. The
122 extra optimization doesn't gain you much, it may provoke compiler
123 bugs, and you won't be able to trace bugs through the C library.
125 `--disable-versioning'
126 Don't compile the shared libraries with symbol version information.
127 Doing this will make the resulting library incompatible with old
128 binaries, so it's not recommended.
130 `--enable-static-nss'
131 Compile static versions of the NSS (Name Service Switch) libraries.
132 This is not recommended because it defeats the purpose of NSS; a
133 program linked statically with the NSS libraries cannot be
134 dynamically reconfigured to use a different name database.
136 `--build=BUILD-SYSTEM'
138 These options are for cross-compiling. If you specify both
139 options and BUILD-SYSTEM is different from HOST-SYSTEM, `configure'
140 will prepare to cross-compile glibc from BUILD-SYSTEM to be used
141 on HOST-SYSTEM. You'll probably need the `--with-headers' option
142 too, and you may have to override CONFIGURE's selection of the
143 compiler and/or binutils.
145 If you only specify `--host', configure will prepare for a native
146 compile but use what you specify instead of guessing what your
147 system is. This is most useful to change the CPU submodel. For
148 example, if configure guesses your machine as `i586-pc-linux-gnu'
149 but you want to compile a library for 386es, give
150 `--host=i386-pc-linux-gnu' or just `--host=i386-linux' and add the
151 appropriate compiler flags (`-mcpu=i386' will do the trick) to
154 If you specify just `--build', configure will get confused.
156 To build the library and related programs, type `make'. This will
157 produce a lot of output, some of which may look like errors from `make'
158 but isn't. Look for error messages from `make' containing `***'.
159 Those indicate that something is really wrong.
161 The compilation process takes several hours even on fast hardware.
162 Expect at least two hours for the default configuration on i586 for
163 Linux. For Hurd times are much longer. Except for EGCS 1.1 and GCC
164 2.95 (and later versions of GCC), all supported versions of GCC have a
165 problem which causes them to take several minutes to compile certain
166 files in the iconvdata directory. Do not panic if the compiler appears
169 If you want to run a parallel make, you can't just give `make' the
170 `-j' option, because it won't be passed down to the sub-makes.
171 Instead, edit the generated `Makefile' and uncomment the line
173 # PARALLELMFLAGS = -j 4
175 You can change the `4' to some other number as appropriate for your
176 system. Instead of changing the `Makefile', you could give this option
177 directly to `make' and call it as, for example, `make
178 PARALLELMFLAGS=-j4'. If you're building in the source directory, you
179 must use the latter approach since in this case no new `Makefile' is
180 generated for you to change.
182 To build and run test programs which exercise some of the library
183 facilities, type `make check'. If it does not complete successfully,
184 do not use the built library, and report a bug after verifying that the
185 problem is not already known. *Note Reporting Bugs::, for instructions
186 on reporting bugs. Note that some of the tests assume they are not
187 being run by `root'. We recommend you compile and test glibc as an
190 To format the `GNU C Library Reference Manual' for printing, type
191 `make dvi'. You need a working TeX installation to do this. The
192 distribution already includes the on-line formatted version of the
193 manual, as Info files. You can regenerate those with `make info', but
194 it shouldn't be necessary.
196 The library has a number of special-purpose configuration parameters
197 which you can find in `Makeconfig'. These can be overwritten with the
198 file `configparms'. To change them, create a `configparms' in your
199 build directory and add values as appropriate for your system. The
200 file is included and parsed by `make' and has to follow the conventions
203 It is easy to configure the GNU C library for cross-compilation by
204 setting a few variables in `configparms'. Set `CC' to the
205 cross-compiler for the target you configured the library for; it is
206 important to use this same `CC' value when running `configure', like
207 this: `CC=TARGET-gcc configure TARGET'. Set `BUILD_CC' to the compiler
208 to use for for programs run on the build system as part of compiling
209 the library. You may need to set `AR' and `RANLIB' to cross-compiling
210 versions of `ar' and `ranlib' if the native tools are not configured to
211 work with object files for the target you configured for.
213 Installing the C Library
214 ========================
216 To install the library and its header files, and the Info files of
217 the manual, type `make install'. This will build things if necessary,
218 before installing them. However, you should still compile everything
219 first. If you are installing glibc as your primary C library, we
220 recommend that you shut the system down to single-user mode first, and
221 reboot afterward. This minimizes the risk of breaking things when the
222 library changes out from underneath.
224 If you're upgrading from Linux libc5 or some other C library, you
225 need to replace the `/usr/include' with a fresh directory before
226 installing it. The new `/usr/include' should contain the Linux
227 headers, but nothing else.
229 You must first build the library (`make'), optionally check it
230 (`make check'), switch the include directories and then install (`make
231 install'). The steps must be done in this order. Not moving the
232 directory before install will result in an unusable mixture of header
233 files from both libraries, but configuring, building, and checking the
234 library requires the ability to compile and run programs against the old
237 If you are upgrading from a previous installation of glibc 2.0 or
238 2.1, `make install' will do the entire job. You do not need to remove
239 the old includes - if you want to do so anyway you must then follow the
242 You may also need to reconfigure GCC to work with the new library.
243 The easiest way to do that is to figure out the compiler switches to
244 make it work again (`-Wl,--dynamic-linker=/lib/ld-linux.so.2' should
245 work on Linux systems) and use them to recompile gcc. You can also
246 edit the specs file (`/usr/lib/gcc-lib/TARGET/VERSION/specs'), but that
247 is a bit of a black art.
249 You can install glibc somewhere other than where you configured it
250 to go by setting the `install_root' variable on the command line for
251 `make install'. The value of this variable is prepended to all the
252 paths for installation. This is useful when setting up a chroot
253 environment or preparing a binary distribution. The directory should be
254 specified with an absolute file name.
256 Glibc 2.1 includes two daemons, `nscd' and `utmpd', which you may or
257 may not want to run. `nscd' caches name service lookups; it can
258 dramatically improve performance with NIS+, and may help with DNS as
259 well. `utmpd' allows programs that use the old format for the `utmp'
260 file to coexist with new programs. For more information see the file
261 `login/README.utmpd'.
263 One auxiliary program, `/usr/libexec/pt_chown', is installed setuid
264 `root'. This program is invoked by the `grantpt' function; it sets the
265 permissions on a pseudoterminal so it can be used by the calling
266 process. This means programs like `xterm' and `screen' do not have to
267 be setuid to get a pty. (There may be other reasons why they need
268 privileges.) If you are using a 2.1 or newer Linux kernel with the
269 `devptsfs' or `devfs' filesystems providing pty slaves, you don't need
270 this program; otherwise you do. The source for `pt_chown' is in
271 `login/programs/pt_chown.c'.
273 After installation you might want to configure the timezone and
274 locale installation of your system. The GNU C library comes with a
275 locale database which gets configured with `localedef'. For example, to
276 set up a German locale with name `de_DE', simply issue the command
277 `localedef -i de_DE -f ISO-8859-1 de_DE'. To configure all locales
278 that are supported by glibc, you can issue from your build directory the
279 command `make localedata/install-locales'.
281 To configure the locally used timezone, you can either set the `TZ'
282 environment variable. The script `tzselect' helps you to select the
283 right value. As an example for Germany, tzselect would tell you to use
284 `TZ='Europe/Berlin''. For a system wide installation (the given paths
285 are for an installation with `--prefix=/usr'), link the timezone file
286 which is in `/usr/share/zoneinfo' to the file `/etc/localtime'. For
287 Germany, you might execute `ln -s /usr/share/zoneinfo/Europe/Berlin
290 Recommended Tools for Compilation
291 =================================
293 We recommend installing the following GNU tools before attempting to
294 build the GNU C library:
298 You need the latest version of GNU `make'. Modifying the GNU C
299 Library to work with other `make' programs would be so difficult
300 that we recommend you port GNU `make' instead. *Really.* We
301 recommend version GNU `make' version 3.75 or 3.77. All earlier
302 versions have severe bugs or lack features. Version 3.76 is known
303 to have bugs which only show up in big projects like GNU `libc'.
304 Version 3.76.1 seems OK but some people have reported problems.
306 * EGCS 1.1.1, 1.1 or 1.0.3, or GCC 2.8.1, 2.95 or newer
308 The GNU C library can only be compiled with the GNU C compiler
309 family. As of the 2.1 release, EGCS 1.0.3 or higher is required.
310 GCC 2.8.1 can also be used (but see the FAQ for reasons why you
311 might not want to). Earlier versions simply are too buggy. As of
312 this writing, GCC 2.95.2 is the compiler we advise to use.
314 You can use whatever compiler you like to compile programs that
315 use GNU libc, but be aware that both GCC 2.7 and 2.8 have bugs in
316 their floating-point support that may be triggered by the math
319 On Alpha machines you need at least EGCS 1.1.1. Earlier versions
322 For PPC you might need some patches even on top of the last EGCS
323 version. See the FAQ.
325 * GNU `binutils' 2.9.1, 2.9.1.0.16, or later 2.9.1.0.x release
327 You must use GNU binutils (as and ld) if you want to build a shared
328 library. Even if you don't, we recommend you use them anyway. No
329 one has tested compilation with non-GNU binutils in a long time.
331 The quality of binutils releases has varied a bit recently. The
332 bugs are in obscure features, but glibc uses quite a few of those.
333 2.9.1, 2.9.1.0.16, and later 2.9.1.0.x releases are known to
334 work. Versions after 2.8.1.0.23 may or may not work. Older
335 versions definitely don't. 2.9.1.0.16 or higher is required on
336 some platforms, like PPC and Arm.
338 For PPC you might need some patches even on top of the last
339 binutils version. See the FAQ.
341 * GNU `texinfo' 3.12f
343 To correctly translate and install the Texinfo documentation you
344 need this version of the `texinfo' package. Earlier versions do
345 not understand all the tags used in the document, and the
346 installation mechanism for the info files is not present or works
349 * GNU `awk' 3.0, or some other POSIX awk
351 Awk is used in several places to generate files. The scripts
352 should work with any POSIX-compliant awk implementation; `gawk'
353 3.0 and `mawk' 1.3 are known to work.
357 Perl is not required, but it is used if present to test the
358 installation. We may decide to use it elsewhere in the future.
360 * GNU `sed' 3.02 or newer
362 Sed is used in several places to generate files. Most scripts
363 work with any version of `sed'. The known exception is the script
364 `po2test.sed' in the `intl' subdirectory which is used to generate
365 `msgs.h' for the testsuite. This script works correctly only with
366 GNU `sed' 3.02. If you like to run the testsuite, you should
367 definitly upgrade `sed'.
370 If you change any of the `configure.in' files you will also need
372 * GNU `autoconf' 2.12 or higher
374 and if you change any of the message translation files you will need
376 * GNU `gettext' 0.10.35 or later (version 0.10.35 is a alpha release
377 and available via ftp from alpha.gnu.org/gnu)
379 You may also need these packages if you upgrade your source tree using
380 patches, although we try to avoid this.
382 Supported Configurations
383 ========================
385 The GNU C Library currently supports configurations that match the
399 Former releases of this library (version 1.09.1 and perhaps earlier
400 versions) used to run on the following configurations:
411 iX86-force_cpu386-none
425 Since no one has volunteered to test and fix these configurations,
426 they are not supported at the moment. They probably don't compile;
427 they definitely don't work anymore. Porting the library is not hard.
428 If you are interested in doing a port, please contact the glibc
429 maintainers by sending electronic mail to <bug-glibc@gnu.org>.
431 Valid cases of `iX86' include `i386', `i486', `i586', and `i686'.
432 All of those configurations produce a library that can run on this
433 processor and newer processors. The GCC compiler by default generates
434 code that's optimized for the machine it's configured for and will use
435 the instructions available on that machine. For example if your GCC is
436 configured for `i686', gcc will optimize for `i686' and might issue
437 some `i686' specific instructions. To generate code for other models,
438 you have to configure for that model and give GCC the appropriate
439 `-march=' and `-mcpu=' compiler switches via CFLAGS.
441 Specific advice for Linux systems
442 =================================
444 If you are installing GNU libc on a Linux system, you need to have
445 the header files from a 2.2 kernel around for reference. You do not
446 need to use the 2.2 kernel, just have its headers where glibc can access
447 at them. The easiest way to do this is to unpack it in a directory
448 such as `/usr/src/linux-2.2.1'. In that directory, run `make config'
449 and accept all the defaults. Then run `make include/linux/version.h'.
450 Finally, configure glibc with the option
451 `--with-headers=/usr/src/linux-2.2.1/include'. Use the most recent
452 kernel you can get your hands on.
454 An alternate tactic is to unpack the 2.2 kernel and run `make
455 config' as above. Then rename or delete `/usr/include', create a new
456 `/usr/include', and make the usual symbolic links of
457 `/usr/include/linux' and `/usr/include/asm' into the 2.2 kernel
458 sources. You can then configure glibc with no special options. This
459 tactic is recommended if you are upgrading from libc5, since you need
460 to get rid of the old header files anyway.
462 Note that `/usr/include/net' and `/usr/include/scsi' should *not* be
463 symlinks into the kernel sources. GNU libc provides its own versions
466 Linux expects some components of the libc installation to be in
467 `/lib' and some in `/usr/lib'. This is handled automatically if you
468 configure glibc with `--prefix=/usr'. If you set some other prefix or
469 allow it to default to `/usr/local', then all the components are
472 If you are upgrading from libc5, you need to recompile every shared
473 library on your system against the new library for the sake of new code,
474 but keep the old libraries around for old binaries to use. This is
475 complicated and difficult. Consult the Glibc2 HOWTO at
476 <http://www.imaxx.net/~thrytis/glibc> for details.
478 You cannot use `nscd' with 2.0 kernels, due to bugs in the
479 kernel-side thread support. `nscd' happens to hit these bugs
480 particularly hard, but you might have problems with any threaded
486 There are probably bugs in the GNU C library. There are certainly
487 errors and omissions in this manual. If you report them, they will get
488 fixed. If you don't, no one will ever know about them and they will
489 remain unfixed for all eternity, if not longer.
491 It is a good idea to verify that the problem has not already been
492 reported. Bugs are documented in two places: The file `BUGS' describes
493 a number of well known bugs and the bug tracking system has a WWW
494 interface at <http://www-gnats.gnu.org:8080/cgi-bin/wwwgnats.pl>. The
495 WWW interface gives you access to open and closed reports. The closed
496 reports normally include a patch or a hint on solving the problem.
498 To report a bug, first you must find it. Hopefully, this will be the
499 hard part. Once you've found a bug, make sure it's really a bug. A
500 good way to do this is to see if the GNU C library behaves the same way
501 some other C library does. If so, probably you are wrong and the
502 libraries are right (but not necessarily). If not, one of the libraries
503 is probably wrong. It might not be the GNU library. Many historical
504 Unix C libraries permit things that we don't, such as closing a file
507 If you think you have found some way in which the GNU C library does
508 not conform to the ISO and POSIX standards (*note Standards and
509 Portability::), that is definitely a bug. Report it!
511 Once you're sure you've found a bug, try to narrow it down to the
512 smallest test case that reproduces the problem. In the case of a C
513 library, you really only need to narrow it down to one library function
514 call, if possible. This should not be too difficult.
516 The final step when you have a simple test case is to report the bug.
517 Do this using the `glibcbug' script. It is installed with libc, or if
518 you haven't installed it, will be in your build directory. Send your
519 test case, the results you got, the results you expected, and what you
520 think the problem might be (if you've thought of anything). `glibcbug'
521 will insert the configuration information we need to see, and ship the
522 report off to <bugs@gnu.org>. Don't send a message there directly; it
523 is fed to a program that expects mail to be formatted in a particular
526 If you are not sure how a function should behave, and this manual
527 doesn't tell you, that's a bug in the manual. Report that too! If the
528 function's behavior disagrees with the manual, then either the library
529 or the manual has a bug, so report the disagreement. If you find any
530 errors or omissions in this manual, please report them to the Internet
531 address <bug-glibc-manual@gnu.org>. If you refer to specific sections
532 of the manual, please include the section names for easier