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'd advise to
36 build in a separate build directory. For example, if you have unpacked
37 the glibc sources in `/src/gnu/glibc-2.1.0', create a directory
38 `/src/gnu/glibc-build' to put the object files in.
40 From your object directory, run the shell script `configure' found
41 at the top level of the source tree. In the scenario above, you'd type
43 $ ../glibc-2.1.0/configure ARGS...
45 Please note that even if you're building in a separate build
46 directory, the compiliation needs to modify a few files in the source
47 directory, especially some files in the manual subdirectory.
49 `configure' takes many options, but you can get away with knowing only
50 two: `--prefix' and `--enable-add-ons'. The `--prefix' option tells
51 configure where you want glibc installed. This defaults to
52 `/usr/local'. The `--enable-add-ons' option tells configure to use all
53 the add-on bundles it finds in the source directory. Since important
54 functionality is provided in add-ons, you should always give this
57 It may also be useful to set the CC and CFLAGS variables in the
58 environment when running `configure'. CC selects the C compiler that
59 will be used, and CFLAGS sets optimization options for the compiler.
61 Here are all the useful options known by `configure':
64 Install machine-independent data files in subdirectories of
65 `DIRECTORY'. The default is to install in `/usr/local'.
67 `--exec-prefix=DIRECTORY'
68 Install the library and other machine-dependent files in
69 subdirectories of `DIRECTORY'. The default is to the `--prefix'
70 directory if that option is given, or `/usr/local' otherwise.
72 `--with-headers=DIRECTORY'
73 Look for kernel header files in DIRECTORY, not `/usr/include'.
74 Glibc needs information from the kernel's private header files.
75 It will normally look in `/usr/include' for them, but if you give
76 this option, it will look in DIRECTORY instead.
78 This option is primarily of use on a system where the headers in
79 `/usr/include' come from an older version of glibc. Conflicts can
80 occasionally happen in this case. Note that Linux libc5 qualifies
81 as an older version of glibc. You can also use this option if you
82 want to compile glibc with a newer set of kernel headers than the
83 ones found in `/usr/include'.
85 `--enable-add-ons[=LIST]'
86 Enable add-on packages in your source tree. If this option is
87 given with no list, it enables all the add-on packages it finds.
88 If you do not wish to use some add-on package that you have
89 present in your source tree, give this option a list of the
90 add-ons that you *do* want used, like this:
91 `--enable-add-ons=crypt,linuxthreads'
93 `--with-binutils=DIRECTORY'
94 Use the binutils (assembler and linker) in `DIRECTORY', not the
95 ones the C compiler would default to. You could use this option if
96 the default binutils on your system cannot deal with all the
97 constructs in the GNU C library. (`configure' will detect the
98 problem and suppress these constructs, so the library will still
99 be usable, but functionality may be lost--for example, you can not
100 build a shared libc with old binutils.)
103 Use this option if your computer lacks hardware floating-point
104 support and your operating system does not emulate an FPU.
107 Don't build shared libraries even if we could. Not all systems
108 support shared libraries; you need ELF support and (currently) the
112 Don't build libraries with profiling information. You may want to
113 use this option if you don't plan to do profiling.
116 Use maximum optimization for the normal (static and shared)
117 libraries, and compile separate static libraries with debugging
118 information and no optimisation. We recommend against this. The
119 extra optimization doesn't gain you much, it may provoke compiler
120 bugs, and you won't be able to trace bugs through the C library.
122 `--disable-versioning'
123 Don't compile the shared libraries with symbol version information.
124 Doing this will make the library that's built incompatible with old
125 binaries, so it's not recommended.
127 `--enable-static-nss'
128 Compile static versions of the NSS (Name Service Switch) libraries.
129 This is not recommended because it defeats the purpose of NSS; a
130 program linked statically with the NSS libraries cannot be
131 dynamically reconfigured to use a different name database.
133 `--build=BUILD-SYSTEM'
135 These options are for cross-compiling. If you give them both and
136 BUILD-SYSTEM is different from HOST-SYSTEM, `configure' will
137 prepare to cross-compile glibc from BUILD-SYSTEM to be used on
138 HOST-SYSTEM. You'll probably need the `--with-headers' option
139 too, and you may have to override CONFIGURE's selection of the
140 compiler and/or binutils.
142 If you give just `--host', configure will prepare for a native
143 compile but use what you say instead of guessing what your system
144 is. This is most useful to change the CPU submodel. For example,
145 if configure guesses your machine as `i586-pc-linux-gnu' but you
146 want to compile a library optimized for 386es, give
147 `--host=i386-pc-linux-gnu' or just `--host=i386-linux'. (A
148 library compiled for a Pentium (`i586') will still work on a 386,
149 but it may be slower.)
151 If you give just `--build', configure will get confused.
153 To build the library and related programs, type `make'. This will
154 produce a lot of output, some of which may look like errors from `make'
155 but isn't. Look for error messages from `make' containing `***'.
156 Those indicate that something is really wrong.
158 The compilation process takes several hours even on fast hardware.
159 Expect at least two hours for the default configuration on i586 for
160 Linux. For Hurd times are much longer. Except for EGCS 1.1 (and later
161 versions of EGCS), all supported versions of GCC have a problem which
162 causes them to take several minutes to compile certain files in the
163 iconvdata directory. Do not panic if the compiler appears to hang.
165 If you want to run a parallel make, you can't just give `make' the
166 `-j' option, because it won't be passed down to the sub-makes.
167 Instead, edit the generated `Makefile' and uncomment the line
169 # PARALLELMFLAGS = -j 4
171 You can change the `4' to some other number as appropriate for your
172 system. Instead of changing the `Makefile', you could give this option
173 directly to `make' and call it as, e.g. `make PARALLELMFLAGS=-j4'. If
174 you're building in the source directory, you've got to use the latter
175 approach since in this case no new `Makefile' is generated which you
178 To build and run some test programs which exercise some of the
179 library facilities, type `make check'. This should complete
180 successfully; if it doesn't, do not use the built library, and report a
181 bug. *Note Reporting Bugs::, for how to do that. Note that some of
182 the tests assume they are not being run by `root'. We recommend you
183 compile and test glibc as an unprivileged user.
185 To format the `GNU C Library Reference Manual' for printing, type
186 `make dvi'. You need a working TeX installation to do this. The
187 distribution already includes the on-line formatted version of the
188 manual, as Info files. You can regenerate those with `make info', but
189 it shouldn't be necessary.
191 Installing the C Library
192 ========================
194 To install the library and its header files, and the Info files of
195 the manual, type `make install'. This will build things if necessary,
196 before installing them. Don't rely on that; compile everything first.
197 If you are installing glibc as your primary C library, we recommend you
198 shut the system down to single-user mode first, and reboot afterward.
199 This minimizes the risk of breaking things when the library changes out
202 If you are upgrading from a previous installation of glibc 2.0 or
203 2.1, `make install' will do the entire job. If you're upgrading from
204 Linux libc5 or some other C library, you need to rename the old
205 `/usr/include' directory out of the way before running `make install',
206 or you will end up with a mixture of header files from both libraries,
207 and you won't be able to compile anything. You may also need to
208 reconfigure GCC to work with the new library. The easiest way to do
209 that is to figure out the compiler switches to make it work again
210 (`-Wl,--dynamic-linker=/lib/ld-linux.so.2' should work on Linux
211 systems) and use them to recompile gcc. You can also edit the specs
212 file (`/usr/lib/gcc-lib/TARGET/VERSION/specs'), but that is a bit of a
215 You can install glibc somewhere other than where you configured it
216 to go by setting the `install_root' variable on the command line for
217 `make install'. The value of this variable is prepended to all the
218 paths for installation. This is useful when setting up a chroot
219 environment or preparing a binary distribution.
221 Glibc 2.1 includes two daemons, `nscd' and `utmpd', which you may or
222 may not want to run. `nscd' caches name service lookups; it can
223 dramatically improve performance with NIS+, and may help with DNS as
224 well. `utmpd' allows programs that use the old format for the `utmp'
225 file to coexist with new programs. For more information see the file
226 `login/README.utmpd'.
228 One auxiliary program, `/usr/libexec/pt_chown', is installed setuid
229 `root'. This program is invoked by the `grantpt' function; it sets the
230 permissions on a pseudoterminal so it can be used by the calling
231 process. This means programs like `xterm' and `screen' do not have to
232 be setuid to get a pty. (There may be other reasons why they need
233 privileges.) If you are using a 2.1 or newer Linux kernel with the
234 `devptsfs' or `devfs' filesystems providing pty slaves, you don't need
235 this program; otherwise you do. The source for `pt_chown' is in
236 `login/programs/pt_chown.c'.
238 Recommended Tools for Compilation
239 =================================
241 We recommend installing the following GNU tools before attempting to
242 build the GNU C library:
246 You need the latest version of GNU `make'. Modifying the GNU C
247 Library to work with other `make' programs would be so hard that we
248 recommend you port GNU `make' instead. *Really.* We recommend
249 version GNU `make' version 3.75 or 3.77. All earlier versions
250 have severe bugs or lack features. Version 3.76 is known to have
251 bugs which only show up in big projects like GNU `libc'. Version
252 3.76.1 seems OK but some people have reported problems.
254 * EGCS 1.1.1, 1.1 or 1.0.3, or GCC 2.8.1
256 The GNU C library can only be compiled with the GNU C compiler
257 family. As of the 2.1 release, EGCS 1.0.3 or higher is required.
258 GCC 2.8.1 can also be used (but see the FAQ for reasons why you
259 might not want to). Earlier versions simply are too buggy.
261 You can use whatever compiler you like to compile programs that
262 use GNU libc, but be aware that both GCC 2.7 and 2.8 have bugs in
263 their floating-point support that may be triggered by the math
266 On Alpha machines you need at least EGCS 1.1.1. Earlier versions
269 For PPC you might need some patches even on top of the last EGCS
270 version. See the FAQ.
272 * GNU `binutils' 2.9.1, 2.9.1.0.16, or later 2.9.1.0.x release
274 You must use GNU binutils (as and ld) if you want to build a shared
275 library. Even if you don't, we recommend you use them anyway. No
276 one has tested compilation with non-GNU binutils in a long time.
278 The quality of binutils releases has varied a bit recently. The
279 bugs are in obscure features, but glibc uses quite a few of those.
280 2.9.1, 2.9.1.0.16, and later 2.9.1.0.x releases are known to
281 work. Versions after 2.8.1.0.23 may or may not work. Older
282 versions definitely don't. 2.9.1.0.16 or higher is required on
283 some platforms, like PPC and Arm.
285 For PPC you might need some patches even on top of the last
286 binutils version. See the FAQ.
288 * GNU `texinfo' 3.12f
290 To correctly translate and install the Texinfo documentation you
291 need this version of the `texinfo' package. Earlier versions do
292 not understand all the tags used in the document, and the
293 installation mechanism for the info files is not present or works
296 * GNU `awk' 3.0, or some other POSIX awk
298 Awk is used in several places to generate files. The scripts
299 should work with any POSIX-compliant awk implementation; `gawk'
300 3.0 and `mawk' 1.3 are known to work.
304 Perl is not required, but it is used if present to test the
305 installation. We may decide to use it elsewhere in the future.
307 If you change any of the `configure.in' files you will also need
309 * GNU `autoconf' 2.12 or higher
311 and if you change any of the message translation files you will need
313 * GNU `gettext' 0.10.35 or later (version 0.10.35 is a alpha release
314 and available via ftp from alpha.gnu.org/gnu)
316 You may also need these packages if you upgrade your source tree using
317 patches, although we try to avoid this.
319 Supported Configurations
320 ========================
322 The GNU C Library currently supports configurations that match the
336 Former releases of this library (version 1.09.1 and perhaps earlier
337 versions) used to run on the following configurations:
348 iX86-force_cpu386-none
362 Since no one has volunteered to test and fix these configurations,
363 they are not supported at the moment. They probably don't compile;
364 they definitely don't work anymore. Porting the library is not hard.
365 If you are interested in doing a port, please contact the glibc
366 maintainers by sending electronic mail to <bug-glibc@gnu.org>.
368 Each case of `iX86' can be `i386', `i486', `i586', or `i686'. All
369 of those configurations produce a library that can run on any of these
370 processors. The library will be optimized for the specified processor,
371 but will not use instructions not available on all of them. If you
372 want the library to use instructions only available on newer
373 processors, give GCC the appropriate `-m' switches via CFLAGS.
375 Specific advice for Linux systems
376 =================================
378 If you are installing GNU libc on a Linux system, you need to have
379 the header files from a 2.2 kernel around for reference. You do not
380 need to use the 2.2 kernel, just have its headers where glibc can get
381 at them. The easiest way to do this is to unpack it in a directory
382 such as `/usr/src/linux-2.2.1'. In that directory, run `make config'
383 and accept all the defaults. Then run `make include/linux/version.h'.
384 Finally, configure glibc with the option
385 `--with-headers=/usr/src/linux-2.2.1/include'. Use the most recent
386 kernel you can get your hands on.
388 An alternate tactic is to unpack the 2.2 kernel and run `make
389 config' as above. Then rename or delete `/usr/include', create a new
390 `/usr/include', and make the usual symbolic links of
391 `/usr/include/linux' and `/usr/include/asm' into the 2.2 kernel
392 sources. You can then configure glibc with no special options. This
393 tactic is recommended if you are upgrading from libc5, since you need
394 to get rid of the old header files anyway.
396 Note that `/usr/include/net' and `/usr/include/scsi' should *not* be
397 symlinks into the kernel sources. GNU libc provides its own versions
400 Linux expects some components of the libc installation to be in
401 `/lib' and some in `/usr/lib'. This is handled automatically if you
402 configure glibc with `--prefix=/usr'. If you set some other prefix or
403 allow it to default to `/usr/local', then all the components are
406 If you are upgrading from libc5, you need to recompile every shared
407 library on your system against the new library for the sake of new code,
408 but keep the old libraries around for old binaries to use. This is
409 complicated and difficult. Consult the Glibc2 HOWTO at
410 `http://www.imaxx.net/~thrytis/glibc' for details.
412 You cannot use `nscd' with 2.0 kernels, due to bugs in the
413 kernel-side thread support. `nscd' happens to hit these bugs
414 particularly hard, but you might have problems with any threaded
420 There are probably bugs in the GNU C library. There are certainly
421 errors and omissions in this manual. If you report them, they will get
422 fixed. If you don't, no one will ever know about them and they will
423 remain unfixed for all eternity, if not longer.
425 It is a good idea to check first that the problem was not reported
426 before. Bugs are documented in two places: The file `BUGS' describes a
427 number of well known bugs and the bug tracking system has a WWW
428 interface at `http://www-gnats.gnu.org:8080/cgi-bin/wwwgnats.pl'. The
429 WWW interface gives you access to open and closed reports. The closed
430 reports normally include a patch or a hint on solving the problem.
432 To report a bug, first you must find it. Hopefully, this will be the
433 hard part. Once you've found a bug, make sure it's really a bug. A
434 good way to do this is to see if the GNU C library behaves the same way
435 some other C library does. If so, probably you are wrong and the
436 libraries are right (but not necessarily). If not, one of the libraries
437 is probably wrong. It might not be the GNU library. Many historical
438 Unix C libraries permit things that we don't, such as closing a file
441 If you think you have found some way in which the GNU C library does
442 not conform to the ISO and POSIX standards (*note Standards and
443 Portability::.), that is definitely a bug. Report it!
445 Once you're sure you've found a bug, try to narrow it down to the
446 smallest test case that reproduces the problem. In the case of a C
447 library, you really only need to narrow it down to one library function
448 call, if possible. This should not be too difficult.
450 The final step when you have a simple test case is to report the bug.
451 Do this using the `glibcbug' script. It is installed with libc, or if
452 you haven't installed it, will be in your build directory. Send your
453 test case, the results you got, the results you expected, and what you
454 think the problem might be (if you've thought of anything). `glibcbug'
455 will insert the configuration information we need to see, and ship the
456 report off to <bugs@gnu.org>. Don't send a message there directly; it
457 is fed to a program that expects mail to be formatted in a particular
460 If you are not sure how a function should behave, and this manual
461 doesn't tell you, that's a bug in the manual. Report that too! If the
462 function's behavior disagrees with the manual, then either the library
463 or the manual has a bug, so report the disagreement. If you find any
464 errors or omissions in this manual, please report them to the Internet
465 address <bug-glibc-manual@gnu.org>. If you refer to specific sections
466 when reporting on the manual, please include the section names for
467 easier identification.