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 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 to remove the whole build directory in case an error occurs
40 which is the safest way to get a clean way 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 compiliation 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 give 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 Here are all the useful options known by `configure':
66 Install machine-independent data files in subdirectories of
67 `DIRECTORY'. The default is to install in `/usr/local'.
69 `--exec-prefix=DIRECTORY'
70 Install the library and other machine-dependent files in
71 subdirectories of `DIRECTORY'. The default is to the `--prefix'
72 directory if that option is given, or `/usr/local' otherwise.
74 `--with-headers=DIRECTORY'
75 Look for kernel header files in DIRECTORY, not `/usr/include'.
76 Glibc needs information from the kernel's private header files.
77 It will normally look in `/usr/include' for them, but if you give
78 this option, it will look in DIRECTORY instead.
80 This option is primarily of use on a system where the headers in
81 `/usr/include' come from an older version of glibc. Conflicts can
82 occasionally happen in this case. Note that Linux libc5 qualifies
83 as an older version of glibc. You can also use this option if you
84 want to compile glibc with a newer set of kernel headers than the
85 ones found in `/usr/include'.
87 `--enable-add-ons[=LIST]'
88 Enable add-on packages in your source tree. If this option is
89 given with no list, it enables all the add-on packages it finds.
90 If you do not wish to use some add-on package that you have
91 present in your source tree, give this option a list of the
92 add-ons that you _do_ want used, like this:
93 `--enable-add-ons=crypt,linuxthreads'
95 `--with-binutils=DIRECTORY'
96 Use the binutils (assembler and linker) in `DIRECTORY', not the
97 ones the C compiler would default to. You could use this option if
98 the default binutils on your system cannot deal with all the
99 constructs in the GNU C library. (`configure' will detect the
100 problem and suppress these constructs, so the library will still
101 be usable, but functionality may be lost--for example, you can not
102 build a shared libc with old binutils.)
105 Use this option if your computer lacks hardware floating-point
106 support and your operating system does not emulate an FPU.
109 Don't build shared libraries even if we could. Not all systems
110 support shared libraries; you need ELF support and (currently) the
114 Don't build libraries with profiling information. You may want to
115 use this option if you don't plan to do profiling.
118 Use maximum optimization for the normal (static and shared)
119 libraries, and compile separate static libraries with debugging
120 information and no optimisation. We recommend against this. The
121 extra optimization doesn't gain you much, it may provoke compiler
122 bugs, and you won't be able to trace bugs through the C library.
124 `--disable-versioning'
125 Don't compile the shared libraries with symbol version information.
126 Doing this will make the library that's built 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.
135 `--build=BUILD-SYSTEM'
137 These options are for cross-compiling. If you give them both and
138 BUILD-SYSTEM is different from HOST-SYSTEM, `configure' will
139 prepare to cross-compile glibc from BUILD-SYSTEM to be used on
140 HOST-SYSTEM. You'll probably need the `--with-headers' option
141 too, and you may have to override CONFIGURE's selection of the
142 compiler and/or binutils.
144 If you give just `--host', configure will prepare for a native
145 compile but use what you say instead of guessing what your system
146 is. This is most useful to change the CPU submodel. For example,
147 if configure guesses your machine as `i586-pc-linux-gnu' but you
148 want to compile a library optimized for 386es, give
149 `--host=i386-pc-linux-gnu' or just `--host=i386-linux' and add the
150 appropriate compiler flags (`-mcpu=i386' will do the trick) to
151 CFLAGS. (A library compiled for a Pentium (`i586') will still work
152 on a 386, but it may be slower.)
154 If you give 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 later
164 versions of EGCS), all supported versions of GCC have a problem which
165 causes them to take several minutes to compile certain files in the
166 iconvdata directory. Do not panic if the compiler appears to hang.
168 If you want to run a parallel make, you can't just give `make' the
169 `-j' option, because it won't be passed down to the sub-makes.
170 Instead, edit the generated `Makefile' and uncomment the line
172 # PARALLELMFLAGS = -j 4
174 You can change the `4' to some other number as appropriate for your
175 system. Instead of changing the `Makefile', you could give this option
176 directly to `make' and call it as, e.g. `make PARALLELMFLAGS=-j4'. If
177 you're building in the source directory, you've got to use the latter
178 approach since in this case no new `Makefile' is generated which you
181 To build and run some test programs which exercise some of the
182 library facilities, type `make check'. This should complete
183 successfully; if it doesn't, do not use the built library, and report a
184 bug. *Note Reporting Bugs::, for how to do that. Note that some of
185 the tests assume they are not being run by `root'. We recommend you
186 compile and test glibc as an unprivileged user.
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 Installing the C Library
195 ========================
197 To install the library and its header files, and the Info files of
198 the manual, type `make install'. This will build things if necessary,
199 before installing them. Don't rely on that; compile everything first.
200 If you are installing glibc as your primary C library, we recommend you
201 shut the system down to single-user mode first, and reboot afterward.
202 This minimizes the risk of breaking things when the library changes out
205 If you are upgrading from a previous installation of glibc 2.0 or
206 2.1, `make install' will do the entire job. If you're upgrading from
207 Linux libc5 or some other C library, you need to rename the old
208 `/usr/include' directory out of the way before running `make install',
209 or you will end up with a mixture of header files from both libraries,
210 and you won't be able to compile anything. You may also need to
211 reconfigure GCC to work with the new library. The easiest way to do
212 that is to figure out the compiler switches to make it work again
213 (`-Wl,--dynamic-linker=/lib/ld-linux.so.2' should work on Linux
214 systems) and use them to recompile gcc. You can also edit the specs
215 file (`/usr/lib/gcc-lib/TARGET/VERSION/specs'), but that is a bit of a
218 You can install glibc somewhere other than where you configured it
219 to go by setting the `install_root' variable on the command line for
220 `make install'. The value of this variable is prepended to all the
221 paths for installation. This is useful when setting up a chroot
222 environment or preparing a binary distribution.
224 Glibc 2.1 includes two daemons, `nscd' and `utmpd', which you may or
225 may not want to run. `nscd' caches name service lookups; it can
226 dramatically improve performance with NIS+, and may help with DNS as
227 well. `utmpd' allows programs that use the old format for the `utmp'
228 file to coexist with new programs. For more information see the file
229 `login/README.utmpd'.
231 One auxiliary program, `/usr/libexec/pt_chown', is installed setuid
232 `root'. This program is invoked by the `grantpt' function; it sets the
233 permissions on a pseudoterminal so it can be used by the calling
234 process. This means programs like `xterm' and `screen' do not have to
235 be setuid to get a pty. (There may be other reasons why they need
236 privileges.) If you are using a 2.1 or newer Linux kernel with the
237 `devptsfs' or `devfs' filesystems providing pty slaves, you don't need
238 this program; otherwise you do. The source for `pt_chown' is in
239 `login/programs/pt_chown.c'.
241 Recommended Tools for Compilation
242 =================================
244 We recommend installing the following GNU tools before attempting to
245 build the GNU C library:
249 You need the latest version of GNU `make'. Modifying the GNU C
250 Library to work with other `make' programs would be so hard that we
251 recommend you port GNU `make' instead. *Really.* We recommend
252 version GNU `make' version 3.75 or 3.77. All earlier versions
253 have severe bugs or lack features. Version 3.76 is known to have
254 bugs which only show up in big projects like GNU `libc'. Version
255 3.76.1 seems OK but some people have reported problems.
257 * EGCS 1.1.1, 1.1 or 1.0.3, or GCC 2.8.1
259 The GNU C library can only be compiled with the GNU C compiler
260 family. As of the 2.1 release, EGCS 1.0.3 or higher is required.
261 GCC 2.8.1 can also be used (but see the FAQ for reasons why you
262 might not want to). Earlier versions simply are too buggy.
264 You can use whatever compiler you like to compile programs that
265 use GNU libc, but be aware that both GCC 2.7 and 2.8 have bugs in
266 their floating-point support that may be triggered by the math
269 On Alpha machines you need at least EGCS 1.1.1. Earlier versions
272 For PPC you might need some patches even on top of the last EGCS
273 version. See the FAQ.
275 * GNU `binutils' 2.9.1, 2.9.1.0.16, or later 2.9.1.0.x release
277 You must use GNU binutils (as and ld) if you want to build a shared
278 library. Even if you don't, we recommend you use them anyway. No
279 one has tested compilation with non-GNU binutils in a long time.
281 The quality of binutils releases has varied a bit recently. The
282 bugs are in obscure features, but glibc uses quite a few of those.
283 2.9.1, 2.9.1.0.16, and later 2.9.1.0.x releases are known to
284 work. Versions after 2.8.1.0.23 may or may not work. Older
285 versions definitely don't. 2.9.1.0.16 or higher is required on
286 some platforms, like PPC and Arm.
288 For PPC you might need some patches even on top of the last
289 binutils version. See the FAQ.
291 * GNU `texinfo' 3.12f
293 To correctly translate and install the Texinfo documentation you
294 need this version of the `texinfo' package. Earlier versions do
295 not understand all the tags used in the document, and the
296 installation mechanism for the info files is not present or works
299 * GNU `awk' 3.0, or some other POSIX awk
301 Awk is used in several places to generate files. The scripts
302 should work with any POSIX-compliant awk implementation; `gawk'
303 3.0 and `mawk' 1.3 are known to work.
307 Perl is not required, but it is used if present to test the
308 installation. We may decide to use it elsewhere in the future.
311 If you change any of the `configure.in' files you will also need
313 * GNU `autoconf' 2.12 or higher
315 and if you change any of the message translation files you will need
317 * GNU `gettext' 0.10.35 or later (version 0.10.35 is a alpha release
318 and available via ftp from alpha.gnu.org/gnu)
320 You may also need these packages if you upgrade your source tree using
321 patches, although we try to avoid this.
323 Supported Configurations
324 ========================
326 The GNU C Library currently supports configurations that match the
340 Former releases of this library (version 1.09.1 and perhaps earlier
341 versions) used to run on the following configurations:
352 iX86-force_cpu386-none
366 Since no one has volunteered to test and fix these configurations,
367 they are not supported at the moment. They probably don't compile;
368 they definitely don't work anymore. Porting the library is not hard.
369 If you are interested in doing a port, please contact the glibc
370 maintainers by sending electronic mail to <bug-glibc@gnu.org>.
372 Each case of `iX86' can be `i386', `i486', `i586', or `i686'. All
373 of those configurations produce a library that can run on any of these
374 processors if the compiler is configured correctly. The GCC compiler
375 by default generates code that's optimized for the machine it's
376 configured for and will use the instructions available on that machine.
377 For example if your GCC is configured for `i686', gcc will optimize
378 for `i686' and might issue some `i686' specific instructions. To
379 generate code for other models you should give GCC the appropriate
380 `-march=' and `-mcpu=' compiler switches via CFLAGS.
382 Specific advice for Linux systems
383 =================================
385 If you are installing GNU libc on a Linux system, you need to have
386 the header files from a 2.2 kernel around for reference. You do not
387 need to use the 2.2 kernel, just have its headers where glibc can get
388 at them. The easiest way to do this is to unpack it in a directory
389 such as `/usr/src/linux-2.2.1'. In that directory, run `make config'
390 and accept all the defaults. Then run `make include/linux/version.h'.
391 Finally, configure glibc with the option
392 `--with-headers=/usr/src/linux-2.2.1/include'. Use the most recent
393 kernel you can get your hands on.
395 An alternate tactic is to unpack the 2.2 kernel and run `make
396 config' as above. Then rename or delete `/usr/include', create a new
397 `/usr/include', and make the usual symbolic links of
398 `/usr/include/linux' and `/usr/include/asm' into the 2.2 kernel
399 sources. You can then configure glibc with no special options. This
400 tactic is recommended if you are upgrading from libc5, since you need
401 to get rid of the old header files anyway.
403 Note that `/usr/include/net' and `/usr/include/scsi' should *not* be
404 symlinks into the kernel sources. GNU libc provides its own versions
407 Linux expects some components of the libc installation to be in
408 `/lib' and some in `/usr/lib'. This is handled automatically if you
409 configure glibc with `--prefix=/usr'. If you set some other prefix or
410 allow it to default to `/usr/local', then all the components are
413 If you are upgrading from libc5, you need to recompile every shared
414 library on your system against the new library for the sake of new code,
415 but keep the old libraries around for old binaries to use. This is
416 complicated and difficult. Consult the Glibc2 HOWTO at
417 <http://www.imaxx.net/~thrytis/glibc> for details.
419 You cannot use `nscd' with 2.0 kernels, due to bugs in the
420 kernel-side thread support. `nscd' happens to hit these bugs
421 particularly hard, but you might have problems with any threaded
427 There are probably bugs in the GNU C library. There are certainly
428 errors and omissions in this manual. If you report them, they will get
429 fixed. If you don't, no one will ever know about them and they will
430 remain unfixed for all eternity, if not longer.
432 It is a good idea to check first that the problem was not reported
433 before. Bugs are documented in two places: The file `BUGS' describes a
434 number of well known bugs and the bug tracking system has a WWW
435 interface at <http://www-gnats.gnu.org:8080/cgi-bin/wwwgnats.pl>. The
436 WWW interface gives you access to open and closed reports. The closed
437 reports normally include a patch or a hint on solving the problem.
439 To report a bug, first you must find it. Hopefully, this will be the
440 hard part. Once you've found a bug, make sure it's really a bug. A
441 good way to do this is to see if the GNU C library behaves the same way
442 some other C library does. If so, probably you are wrong and the
443 libraries are right (but not necessarily). If not, one of the libraries
444 is probably wrong. It might not be the GNU library. Many historical
445 Unix C libraries permit things that we don't, such as closing a file
448 If you think you have found some way in which the GNU C library does
449 not conform to the ISO and POSIX standards (*note Standards and
450 Portability::.), that is definitely a bug. Report it!
452 Once you're sure you've found a bug, try to narrow it down to the
453 smallest test case that reproduces the problem. In the case of a C
454 library, you really only need to narrow it down to one library function
455 call, if possible. This should not be too difficult.
457 The final step when you have a simple test case is to report the bug.
458 Do this using the `glibcbug' script. It is installed with libc, or if
459 you haven't installed it, will be in your build directory. Send your
460 test case, the results you got, the results you expected, and what you
461 think the problem might be (if you've thought of anything). `glibcbug'
462 will insert the configuration information we need to see, and ship the
463 report off to <bugs@gnu.org>. Don't send a message there directly; it
464 is fed to a program that expects mail to be formatted in a particular
467 If you are not sure how a function should behave, and this manual
468 doesn't tell you, that's a bug in the manual. Report that too! If the
469 function's behavior disagrees with the manual, then either the library
470 or the manual has a bug, so report the disagreement. If you find any
471 errors or omissions in this manual, please report them to the Internet
472 address <bug-glibc-manual@gnu.org>. If you refer to specific sections
473 when reporting on the manual, please include the section names for
474 easier identification.