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.ifi.uio.no'.
24 (Most non-US mirrors of `ftp.gnu.org' will have it too.) The file you
25 need is `glibc-crypt-VERSION.tar.gz'.
27 You will need recent versions of several GNU tools: definitely GCC
28 and GNU Make, and possibly others. *Note Tools for Compilation::,
31 Configuring and compiling GNU Libc
32 ==================================
34 GNU Libc can be compiled in the source directory but we'd advise to
35 build in a separate build directory. For example, if you have unpacked
36 the glibc sources in `/src/gnu/glibc-2.1.0', create a directory
37 `/src/gnu/glibc-build' to put the object files in.
39 From your object directory, run the shell script `configure' found
40 at the top level of the source tree. In the scenario above, you'd type
42 $ ../glibc-2.1.0/configure ARGS...
44 `configure' takes many options, but you can get away with knowing only
45 two: `--prefix' and `--enable-add-ons'. The `--prefix' option tells
46 configure where you want glibc installed. This defaults to
47 `/usr/local'. The `--enable-add-ons' option tells configure to use all
48 the add-on bundles it finds in the source directory. Since important
49 functionality is provided in add-ons, you should always give this
52 It may also be useful to set the CC and CFLAGS variables in the
53 environment when running `configure'. CC selects the C compiler that
54 will be used, and CFLAGS sets optimization options for the compiler.
56 Here are all the useful options known by `configure':
59 Install machine-independent data files in subdirectories of
60 `DIRECTORY'. The default is to install in `/usr/local'.
62 `--exec-prefix=DIRECTORY'
63 Install the library and other machine-dependent files in
64 subdirectories of `DIRECTORY'. The default is to the `--prefix'
65 directory if that option is given, or `/usr/local' otherwise.
67 `--with-headers=DIRECTORY'
68 Look for kernel header files in DIRECTORY, not `/usr/include'.
69 Glibc needs information from the kernel's private header files.
70 It will normally look in `/usr/include' for them, but if you give
71 this option, it will look in DIRECTORY instead.
73 This option is primarily of use on a system where the headers in
74 `/usr/include' come from an older version of glibc. Conflicts can
75 occasionally happen in this case. Note that Linux libc5 qualifies
76 as an older version of glibc. You can also use this option if you
77 want to compile glibc with a newer set of kernel headers than the
78 ones found in `/usr/include'.
80 `--enable-add-ons[=LIST]'
81 Enable add-on packages in your source tree. If this option is
82 given with no list, it enables all the add-on packages it finds.
83 If you do not wish to use some add-on package that you have
84 present in your source tree, give this option a list of the
85 add-ons that you *do* want used, like this:
86 `--enable-add-ons=crypt,linuxthreads'
88 `--with-binutils=DIRECTORY'
89 Use the binutils (assembler and linker) in `DIRECTORY', not the
90 ones the C compiler would default to. You could use this option if
91 the default binutils on your system cannot deal with all the
92 constructs in the GNU C library. (`configure' will detect the
93 problem and suppress these constructs, so the library will still
94 be usable, but functionality may be lost--for example, you can not
95 build a shared libc with old binutils.)
98 Use this option if your computer lacks hardware floating-point
99 support and your operating system does not emulate an FPU.
102 Don't build static libraries. Static libraries aren't that useful
103 these days, but we recommend you build them in case you need them.
106 Don't build shared libraries even if we could. Not all systems
107 support shared libraries; you need ELF support and (currently) the
111 Don't build libraries with profiling information. You may want to
112 use this option if you don't plan to do profiling.
115 Use maximum optimization for the normal (static and shared)
116 libraries, and compile separate static libraries with debugging
117 information and no optimisation. We recommend against this. The
118 extra optimization doesn't gain you much, it may provoke compiler
119 bugs, and you won't be able to trace bugs through the C library.
121 `--disable-versioning'
122 Don't compile the shared libraries with symbol version information.
123 Doing this will make the library that's built incompatible with old
124 binaries, so it's not recommended.
126 `--enable-static-nss'
127 Compile static versions of the NSS (Name Service Switch) libraries.
128 This is not recommended because it defeats the purpose of NSS; a
129 program linked statically with the NSS libraries cannot be
130 dynamically reconfigured to use a different name database.
132 `--build=BUILD-SYSTEM'
134 These options are for cross-compiling. If you give them both and
135 BUILD-SYSTEM is different from HOST-SYSTEM, `configure' will
136 prepare to cross-compile glibc from BUILD-SYSTEM to be used on
137 HOST-SYSTEM. You'll probably need the `--with-headers' option
138 too, and you may have to override CONFIGURE's selection of the
139 compiler and/or binutils.
141 If you give just `--host', configure will prepare for a native
142 compile but use what you say instead of guessing what your system
143 is. This is most useful to change the CPU submodel. For example,
144 if configure guesses your machine as `i586-pc-linux-gnu' but you
145 want to compile a library optimized for 386es, give
146 `--host=i386-pc-linux-gnu' or just `--host=i386-linux'. (A
147 library compiled for a Pentium (`i586') will still work on a 386,
148 but it may be slower.)
150 If you give just `--build', configure will get confused.
152 To build the library and related programs, type `make'. This will
153 produce a lot of output, some of which may look like errors from `make'
154 but isn't. Look for error messages from `make' containing `***'.
155 Those indicate that something is really wrong.
157 The compilation process takes several hours even on fast hardware.
158 Expect at least two hours for the default configuration on i586 for
159 Linux. For Hurd times are much longer. Except for EGCS 1.1 (and later
160 versions of EGCS), all supported versions of GCC have a problem which
161 causes them to take several minutes to compile certain files in the
162 iconvdata directory. Do not panic if the compiler appears to hang.
164 If you want to run a parallel make, you can't just give `make' the
165 `-j' option, because it won't be passed down to the sub-makes.
166 Instead, edit the generated `Makefile' and uncomment the line
168 # PARALLELMFLAGS = -j 4
170 You can change the `4' to some other number as appropriate for your
173 To build and run some test programs which exercise some of the
174 library facilities, type `make check'. This should complete
175 successfully; if it doesn't, do not use the built library, and report a
176 bug. *Note Reporting Bugs::, for how to do that. Note that some of
177 the tests assume they are not being run by `root'. We recommend you
178 compile and test glibc as an unprivileged user.
180 To format the `GNU C Library Reference Manual' for printing, type
181 `make dvi'. You need a working TeX installation to do this. The
182 distribution already includes the on-line formatted version of the
183 manual, as Info files. You can regenerate those with `make info', but
184 it shouldn't be necessary.
186 Installing the C Library
187 ========================
189 To install the library and its header files, and the Info files of
190 the manual, type `make install'. This will build things if necessary,
191 before installing them. Don't rely on that; compile everything first.
192 If you are installing glibc as your primary C library, we recommend you
193 shut the system down to single-user mode first, and reboot afterward.
194 This minimizes the risk of breaking things when the library changes out
197 If you are upgrading from a previous installation of glibc 2.0 or
198 2.1, `make install' will do the entire job. If you're upgrading from
199 Linux libc5 or some other C library, you need to rename the old
200 `/usr/include' directory out of the way first, or you will end up with
201 a mixture of header files from both libraries, and you won't be able to
202 compile anything. You may also need to reconfigure GCC to work with
203 the new library. The easiest way to do that is to figure out the
204 compiler switches to make it work again
205 (`-Wl,-dynamic-linker=/lib/ld-linux.so.2' should work on Linux systems)
206 and use them to recompile gcc. You can also edit the specs file
207 (`/usr/lib/gcc-lib/TARGET/VERSION/specs'), but that is a bit of a black
210 You can install glibc somewhere other than where you configured it
211 to go by setting the `install_root' variable on the command line for
212 `make install'. The value of this variable is prepended to all the
213 paths for installation. This is useful when setting up a chroot
214 environment or preparing a binary distribution.
216 Glibc 2.1 includes two daemons, `nscd' and `utmpd', which you may or
217 may not want to run. `nscd' caches name service lookups; it can
218 dramatically improve performance with NIS+, and may help with DNS as
219 well. `utmpd' allows programs that use the old format for the `utmp'
220 file to coexist with new programs. For more information see the files
221 `nscd/README' and `login/README.utmpd'.
223 One auxiliary program, `/usr/libexec/pt_chown', is installed setuid
224 `root'. This program is invoked by the `grantpt' function; it sets the
225 permissions on a pseudoterminal so it can be used by the calling
226 process. This means programs like `xterm' and `screen' do not have to
227 be setuid to get a pty. (There may be other reasons why they need
228 privileges.) If you are using a 2.1 or newer Linux kernel with the
229 `devptsfs' or `devfs' filesystems providing pty slaves, you don't need
230 this program; otherwise you do. The source for `pt_chown' is in
231 `login/programs/pt_chown.c'.
233 Recommended Tools for Compilation
234 =================================
236 We recommend installing the following GNU tools before attempting to
237 build the GNU C library:
241 You need the latest version of GNU `make'. Modifying the GNU C
242 Library to work with other `make' programs would be so hard that we
243 recommend you port GNU `make' instead. *Really.* We recommend
244 version GNU `make' version 3.75 or 3.77. All earlier versions
245 have severe bugs or lack features. Version 3.76 is known to have
246 bugs which only show up in big projects like GNU `libc'. Version
247 3.76.1 seems OK but some people have reported problems.
249 * EGCS 1.1.1, 1.1 or 1.0.3
251 The GNU C library can only be compiled with the GNU C compiler
252 family. We recommend EGCS 1.0.3 or higher. GCC 2.8.1 and older
253 versions of EGCS may have problems, particularly on non-Intel
254 architectures. GCC 2.7.x has catastrophic bugs and cannot be used
255 at all. (You can use GCC 2.7.x to compile programs that use GNU
256 libc, but you may have problems, particularly with the math
259 On Alpha machines you need at least EGCS 1.1.1. Earlier versions
262 For PPC you might need some patches even on top of the last EGCS
263 version. See the FAQ.
265 * GNU `binutils' 2.9.1, or 2.9.1.0.16
267 You must use GNU binutils (as and ld) if you want to build a shared
268 library. Even if you don't, we recommend you use them anyway. No
269 one has tested compilation with non-GNU binutils in a long time.
271 The quality of binutils releases has varied a bit recently. The
272 bugs are in obscure features, but glibc uses quite a few of those.
273 2.9.1 and 2.9.1.0.16 are known to work. Versions after 2.8.1.0.23
274 may or may not work. Older versions definitely don't. 2.9.1.0.16
275 is required on some platforms, like PPC and Arm.
277 For PPC you might need some patches even on top of the last
278 binutils version. See the FAQ.
282 To correctly translate and install the Texinfo documentation you
283 need this version of the `texinfo' package. Earlier versions do
284 not understand all the tags used in the document, and the
285 installation mechanism for the info files is not present or works
288 * GNU `awk' 3.0, or some other POSIX awk
290 Awk is used in several places to generate files. The scripts
291 should work with any POSIX-compliant awk implementation; `gawk'
292 3.0 and `mawk' 1.3 are known to work.
296 Perl is not required, but it is used if present to test the
297 installation. We may decide to use it elsewhere in the future.
299 If you change any of the `configure.in' files you will also need
301 * GNU `autoconf' 2.12
303 and if you change any of the message translation files you will need
305 * GNU `gettext' 0.10.35 or later
307 You may also need these packages if you upgrade your source tree using
308 patches, although we try to avoid this.
310 Supported Configurations
311 ========================
313 The GNU C Library currently supports configurations that match the
327 Former releases of this library (version 1.09.1 and perhaps earlier
328 versions) used to run on the following configurations:
339 iX86-force_cpu386-none
353 Since no one has volunteered to test and fix these configurations,
354 they are not supported at the moment. They probably don't compile;
355 they definitely don't work anymore. Porting the library is not hard.
356 If you are interested in doing a port, please contact the glibc
357 maintainers by sending electronic mail to <bug-glibc@gnu.org>.
359 Each case of `iX86' can be `i386', `i486', `i586', or `i686'. All
360 of those configurations produce a library that can run on any of these
361 processors. The library will be optimized for the specified processor,
362 but will not use instructions not available on all of them. If you
363 want the library to use instructions only available on newer
364 processors, give GCC the appropriate `-m' switches via CFLAGS.
366 Specific advice for Linux systems
367 =================================
369 If you are installing GNU libc on a Linux system, you need to have
370 the header files from a development kernel around for reference. You
371 do not need to use the development kernel, just have its headers where
372 glibc can get at them. The easiest way to do this is to unpack a
373 development kernel in a directory such as `/usr/src/linux-dev'. In that
374 directory, run `make config' and accept all the defaults. Then
375 configure glibc with the option
376 `--with-headers=/usr/src/linux-dev/include'. Use the latest
377 development kernel you can get your hands on.
379 An alternate tactic is to unpack the development kernel and run
380 `make config' as above. Then rename or delete `/usr/include', create a
381 new `/usr/include', and make the usual symbolic links of
382 `/usr/include/linux' and `/usr/include/asm' into the development kernel
383 sources. You can then configure glibc with no special options. This
384 tactic is recommended if you are upgrading from libc5, since you need
385 to get rid of the old header files anyway.
387 Note that `/usr/include/net' and `/usr/include/scsi' should *not* be
388 symlinks into the kernel sources. GNU libc provides its own versions
391 Linux expects some components of the libc installation to be in
392 `/lib' and some in `/usr/lib'. This is handled automatically if you
393 configure glibc with `--prefix=/usr'. If you set some other prefix or
394 allow it to default to `/usr/local', then all the components are
397 If you are upgrading from libc5, you need to recompile every shared
398 library on your system against the new library for the sake of new code,
399 but keep the old libraries around for old binaries to use. This is
400 complicated and difficult. Consult the Glibc2 HOWTO at
401 `http://www.imaxx.net/~thrytis/glibc' for details.
403 You cannot use `nscd' with 2.0 kernels, due to bugs in the
404 kernel-side thread support. `nscd' happens to hit these bugs
405 particularly hard, but you might have problems with any threaded
411 There are probably bugs in the GNU C library. There are certainly
412 errors and omissions in this manual. If you report them, they will get
413 fixed. If you don't, no one will ever know about them and they will
414 remain unfixed for all eternity, if not longer.
416 To report a bug, first you must find it. Hopefully, this will be the
417 hard part. Once you've found a bug, make sure it's really a bug. A
418 good way to do this is to see if the GNU C library behaves the same way
419 some other C library does. If so, probably you are wrong and the
420 libraries are right (but not necessarily). If not, one of the libraries
421 is probably wrong. It might not be the GNU library. Many historical
422 Unix C libraries permit things that we don't, such as closing a file
425 If you think you have found some way in which the GNU C library does
426 not conform to the ISO and POSIX standards (*note Standards and
427 Portability::.), that is definitely a bug. Report it!
429 Once you're sure you've found a bug, try to narrow it down to the
430 smallest test case that reproduces the problem. In the case of a C
431 library, you really only need to narrow it down to one library function
432 call, if possible. This should not be too difficult.
434 The final step when you have a simple test case is to report the bug.
435 Do this using the `glibcbug' script. It is installed with libc, or if
436 you haven't installed it, will be in your build directory. Send your
437 test case, the results you got, the results you expected, and what you
438 think the problem might be (if you've thought of anything). `glibcbug'
439 will insert the configuration information we need to see, and ship the
440 report off to <bug-glibc@gnu.org>. Don't send a message there
441 directly; it is fed to a program that expects mail to be formatted in a
442 particular way. Use the script.
444 If you are not sure how a function should behave, and this manual
445 doesn't tell you, that's a bug in the manual. Report that too! If the
446 function's behavior disagrees with the manual, then either the library
447 or the manual has a bug, so report the disagreement. If you find any
448 errors or omissions in this manual, please report them to the Internet
449 address <bug-glibc-manual@gnu.org>. If you refer to specific sections
450 when reporting on the manual, please include the section names for
451 easier identification.