3dcf8ea677
1998-05-21 Ulrich Drepper <drepper@cygnus.com> * iconv/iconv_prog.c (print_known_names): Use strverscmp in all tsearch calls.
1158 lines
46 KiB
Plaintext
1158 lines
46 KiB
Plaintext
Frequently Asked Questions about the GNU C Library
|
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This document tries to answer questions a user might have when installing
|
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and using glibc. Please make sure you read this before sending questions or
|
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bug reports to the maintainers.
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|
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The GNU C library is very complex. The installation process has not been
|
||
completely automated; there are too many variables. You can do substantial
|
||
damage to your system by installing the library incorrectly. Make sure you
|
||
understand what you are undertaking before you begin.
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|
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If you have any questions you think should be answered in this document,
|
||
please let me know.
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--drepper@cygnus.com
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~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
|
||
|
||
1. Compiling glibc
|
||
|
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1.1. What systems does the GNU C Library run on?
|
||
1.2. What compiler do I need to build GNU libc?
|
||
1.3. When I try to compile glibc I get only error messages.
|
||
What's wrong?
|
||
1.4. Do I need a special linker or archiver?
|
||
1.5. Which compiler should I use for powerpc?
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||
1.6. Do I need some more things to compile GNU C Library?
|
||
1.7. What version of the Linux kernel headers should be used?
|
||
1.8. The compiler hangs while building iconvdata modules. What's
|
||
wrong?
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||
1.9. When I run `nm -u libc.so' on the produced library I still
|
||
find unresolved symbols. Can this be ok?
|
||
1.10. What are these `add-ons'?
|
||
1.11. My XXX kernel emulates a floating-point coprocessor for me.
|
||
Should I enable --with-fp?
|
||
1.12. When compiling GNU libc I get lots of errors saying functions
|
||
in glibc are duplicated in libgcc.
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||
1.13. Why do I get messages about missing thread functions when I use
|
||
librt? I don't even use threads.
|
||
1.14. What's the problem with configure --enable-omitfp?
|
||
|
||
2. Installation and configuration issues
|
||
|
||
2.1. Can I replace the libc on my Linux system with GNU libc?
|
||
2.2. How do I configure GNU libc so that the essential libraries
|
||
like libc.so go into /lib and the other into /usr/lib?
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||
2.3. How should I avoid damaging my system when I install GNU libc?
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2.4. Do I need to use GNU CC to compile programs that will use the
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||
GNU C Library?
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2.5. When linking with the new libc I get unresolved symbols
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`crypt' and `setkey'. Why aren't these functions in the
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libc anymore?
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2.6. When I use GNU libc on my Linux system by linking against
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the libc.so which comes with glibc all I get is a core dump.
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2.7. Looking through the shared libc file I haven't found the
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functions `stat', `lstat', `fstat', and `mknod' and while
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linking on my Linux system I get error messages. How is
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this supposed to work?
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2.8. How can I compile gcc 2.7.2.1 from the gcc source code using
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glibc 2.x?
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2.9. The `gencat' utility cannot process the catalog sources which
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were used on my Linux libc5 based system. Why?
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2.10. Programs using libc have their messages translated, but other
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behavior is not localized (e.g. collating order); why?
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2.11. I have set up /etc/nis.conf, and the Linux libc 5 with NYS
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works great. But the glibc NIS+ doesn't seem to work.
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2.12. I have killed ypbind to stop using NIS, but glibc
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continues using NIS.
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2.13. Under Linux/Alpha, I always get "do_ypcall: clnt_call:
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RPC: Unable to receive; errno = Connection refused" when using NIS.
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2.14. After installing glibc name resolving doesn't work properly.
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2.15. How do I create the databases for NSS?
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2.16. I have /usr/include/net and /usr/include/scsi as symlinks
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into my Linux source tree. Is that wrong?
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2.17. Programs like `logname', `top', `uptime' `users', `w' and
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`who', show incorrect information about the (number of)
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users on my system. Why?
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2.18. After upgrading to glibc 2.1 with symbol versioning I get
|
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errors about undefined symbols. What went wrong?
|
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2.19. When I start the program XXX after upgrading the library
|
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I get
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XXX: Symbol `_sys_errlist' has different size in shared
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object, consider re-linking
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Why? What should I do?
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2.20. What do I need for C++ development?
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2.21. Even statically linked programs need some shared libraries
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which is not acceptable for me. What can I do?
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|
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3. Source and binary incompatibilities, and what to do about them
|
||
|
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3.1. I expect GNU libc to be 100% source code compatible with
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the old Linux based GNU libc. Why isn't it like this?
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||
3.2. Why does getlogin() always return NULL on my Linux box?
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||
3.3. Where are the DST_* constants found in <sys/time.h> on many
|
||
systems?
|
||
3.4. The prototypes for `connect', `accept', `getsockopt',
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`setsockopt', `getsockname', `getpeername', `send',
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`sendto', and `recvfrom' are different in GNU libc from
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any other system I saw. This is a bug, isn't it?
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3.5. On Linux I've got problems with the declarations in Linux
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||
kernel headers.
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||
3.6. I don't include any kernel headers myself but the compiler
|
||
still complains about redeclarations of types in the kernel
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||
headers.
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||
3.7. Why don't signals interrupt system calls anymore?
|
||
3.8. I've got errors compiling code that uses certain string
|
||
functions. Why?
|
||
3.9. I get compiler messages "Initializer element not constant" with
|
||
stdin/stdout/stderr. Why?
|
||
3.10. I can't compile with gcc -traditional (or
|
||
-traditional-cpp). Why?
|
||
3.11. I get some errors with `gcc -ansi'. Isn't glibc ANSI compatible?
|
||
3.12. I can't access some functions anymore. nm shows that they do
|
||
exist but linking fails nevertheless.
|
||
|
||
4. Miscellaneous
|
||
|
||
4.1. After I changed configure.in I get `Autoconf version X.Y.
|
||
or higher is required for this script'. What can I do?
|
||
4.2. When I try to compile code which uses IPv6 headers and
|
||
definitions on my Linux 2.x.y system I am in trouble.
|
||
Nothing seems to work.
|
||
4.3. When I set the timezone by setting the TZ environment variable
|
||
to EST5EDT things go wrong since glibc computes the wrong time
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||
from this information.
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||
|
||
|
||
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
|
||
|
||
1. Compiling glibc
|
||
|
||
1.1. What systems does the GNU C Library run on?
|
||
|
||
{UD} This is difficult to answer. The file `README' lists the architectures
|
||
GNU libc was known to run on *at some time*. This does not mean that it
|
||
still can be compiled and run on them now.
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||
|
||
The systems glibc is known to work on as of this release, and most probably
|
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in the future, are:
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||
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||
*-*-gnu GNU Hurd
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||
i[3456]86-*-linux-gnu Linux-2.x on Intel
|
||
m68k-*-linux-gnu Linux-2.x on Motorola 680x0
|
||
alpha-*-linux-gnu Linux-2.x on DEC Alpha
|
||
powerpc-*-linux-gnu Linux and MkLinux on PowerPC systems
|
||
sparc-*-linux-gnu Linux-2.x on SPARC
|
||
sparc64-*-linux-gnu Linux-2.x on UltraSPARC
|
||
arm-*-none ARM standalone systems
|
||
arm-*-linuxaout Linux-2.x on ARM using a.out binaries
|
||
|
||
Ports to other Linux platforms are in development, and may in fact work
|
||
already, but no one has sent us success reports for them. Currently no
|
||
ports to other operating systems are underway, although a few people have
|
||
expressed interest.
|
||
|
||
If you have a system not listed above (or in the `README' file) and you are
|
||
really interested in porting it, contact
|
||
|
||
<bug-glibc@gnu.org>
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||
|
||
|
||
1.2. What compiler do I need to build GNU libc?
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||
|
||
{UD} You must use GNU CC to compile GNU libc. A lot of extensions of GNU CC
|
||
are used to increase portability and speed.
|
||
|
||
GNU CC is found, like all other GNU packages, on
|
||
|
||
ftp://ftp.gnu.org/pub/gnu
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||
|
||
and the many mirror sites. ftp.gnu.org is always overloaded, so try to find
|
||
a local mirror first.
|
||
|
||
You always should try to use the latest official release. Older versions
|
||
may not have all the features GNU libc requires. The current releases of
|
||
egcs (1.0.2) and GNU CC (2.8.1) should work with the GNU C library (for
|
||
powerpc see question question 1.5).
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||
|
||
|
||
1.3. When I try to compile glibc I get only error messages.
|
||
What's wrong?
|
||
|
||
{UD} You definitely need GNU make to translate GNU libc. No other make
|
||
program has the needed functionality.
|
||
|
||
We recommend version GNU make version 3.75. Versions 3.76 and 3.76.1 have
|
||
bugs which appear when building big projects like GNU libc. Versions before
|
||
3.74 have bugs and/or are missing features.
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||
|
||
|
||
1.4. Do I need a special linker or archiver?
|
||
|
||
{UD} You may be able to use your system linker, but GNU libc works best with
|
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GNU binutils.
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||
|
||
On systems where the native linker does not support weak symbols you will
|
||
not get a fully ISO C compliant C library. Generally speaking you should
|
||
use the GNU binutils if they provide at least the same functionality as your
|
||
system's tools.
|
||
|
||
Always get the newest release of GNU binutils available. Older releases are
|
||
known to have bugs that prevent a successful compilation.
|
||
|
||
{ZW} As of release 2.1 a linker supporting symbol versions is required. For
|
||
Linux, get binutils-2.8.1.0.23 or later. Other systems may have native
|
||
linker support, but it's moot right now, because glibc has not been ported
|
||
to them.
|
||
|
||
|
||
1.5. Which compiler should I use for powerpc?
|
||
|
||
{GK} You want to use egcs 1.0.1 or later (together with the right versions
|
||
of all the other tools, of course).
|
||
|
||
In fact, egcs 1.0.1 has a serious bug that prevents a clean make, relating
|
||
to switch statement folding. It also causes the resulting shared libraries
|
||
to use more memory than they should. There is a patch at:
|
||
|
||
<http://discus.anu.edu.au/~geoffk/egcs-1.0.1-geoffk.diff>
|
||
|
||
Later versions of egcs may fix these problems.
|
||
|
||
|
||
1.6. Do I need some more things to compile GNU C Library?
|
||
|
||
{UD} Yes, there are some more :-).
|
||
|
||
* GNU gettext. This package contains the tools needed to construct
|
||
`message catalog' files containing translated versions of system
|
||
messages. See ftp://ftp.gnu.org/pub/gnu or better any mirror
|
||
site. (We distribute compiled message catalogs, but they may not be
|
||
updated in patches.)
|
||
|
||
* Some files depend on special tools. E.g., files ending in .gperf
|
||
need a `gperf' program. The GNU version (part of libg++) is known
|
||
to work while some vendor versions do not.
|
||
|
||
You should not need these tools unless you change the source files.
|
||
|
||
* Some scripts need perl5 - but at the moment those scripts are not
|
||
vital for building and installing GNU libc (some data files will not
|
||
be created).
|
||
|
||
* When compiling for Linux, the header files of the Linux kernel must
|
||
be available to the compiler as <linux/*.h> and <asm/*.h>.
|
||
|
||
* lots of disk space (~170MB for i?86-linux; more for RISC platforms,
|
||
as much as 400MB).
|
||
|
||
* plenty of time. Compiling just the shared and static libraries for
|
||
i?86-linux takes approximately 1h on an i586@133, or 2.5h on
|
||
i486@66, or 4.5h on i486@33. Multiply this by 1.5 or 2.0 if you
|
||
build profiling and/or the highly optimized version as well. For
|
||
Hurd systems times are much higher.
|
||
|
||
You should avoid compiling in a NFS mounted filesystem. This is
|
||
very slow.
|
||
|
||
James Troup <J.J.Troup@comp.brad.ac.uk> reports a compile time of
|
||
45h34m for a full build (shared, static, and profiled) on Atari
|
||
Falcon (Motorola 68030 @ 16 Mhz, 14 Mb memory) and Jan Barte
|
||
<yann@plato.uni-paderborn.de> reports 22h48m on Atari TT030
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||
(Motorola 68030 @ 32 Mhz, 34 Mb memory)
|
||
|
||
If you have some more measurements let me know.
|
||
|
||
|
||
1.7. What version of the Linux kernel headers should be used?
|
||
|
||
{AJ,UD} The headers from the most recent Linux kernel should be used. The
|
||
headers used while compiling the GNU C library and the kernel binary used
|
||
when using the library do not need to match. The GNU C library runs without
|
||
problems on kernels that are older than the kernel headers used. The other
|
||
way round (compiling the GNU C library with old kernel headers and running
|
||
on a recent kernel) does not necessarily work. For example you can't use
|
||
new kernel features when using old kernel headers for compiling the GNU C
|
||
library.
|
||
|
||
|
||
1.8. The compiler hangs while building iconvdata modules. What's
|
||
wrong?
|
||
|
||
{ZW} This is a problem with all current releases of GCC. Initialization of
|
||
large static arrays is very slow. The compiler will eventually finish; give
|
||
it time.
|
||
|
||
The problem will be fixed in egcs 1.1 but probably not before then.
|
||
|
||
|
||
1.9. When I run `nm -u libc.so' on the produced library I still
|
||
find unresolved symbols. Can this be ok?
|
||
|
||
{UD} Yes, this is ok. There can be several kinds of unresolved symbols:
|
||
|
||
* magic symbols automatically generated by the linker. These have names
|
||
like __start_* and __stop_*
|
||
|
||
* symbols starting with _dl_* come from the dynamic linker
|
||
|
||
* weak symbols, which need not be resolved at all (fabs for example)
|
||
|
||
Generally, you should make sure you find a real program which produces
|
||
errors while linking before deciding there is a problem.
|
||
|
||
|
||
1.10. What are these `add-ons'?
|
||
|
||
{UD} To avoid complications with export rules or external source code some
|
||
optional parts of the libc are distributed as separate packages (e.g., the
|
||
crypt package, see question 2.5).
|
||
|
||
To use these packages as part of GNU libc, just unpack the tarfiles in the
|
||
libc source directory and tell the configuration script about them using the
|
||
--enable-add-ons option. If you give just --enable-add-ons configure tries
|
||
to find all the add-on packages in your source tree. This may not work. If
|
||
it doesn't, or if you want to select only a subset of the add-ons, give a
|
||
comma-separated list of the add-ons to enable:
|
||
|
||
configure --enable-add-ons=crypt,linuxthreads
|
||
|
||
for example.
|
||
|
||
Add-ons can add features (including entirely new shared libraries), override
|
||
files, provide support for additional architectures, and just about anything
|
||
else. The existing makefiles do most of the work; only some few stub rules
|
||
must be written to get everything running.
|
||
|
||
|
||
1.11. My XXX kernel emulates a floating-point coprocessor for me.
|
||
Should I enable --with-fp?
|
||
|
||
{ZW} An emulated FPU is just as good as a real one, as far as the C library
|
||
is concerned. You only need to say --without-fp if your machine has no way
|
||
to execute floating-point instructions.
|
||
|
||
People who are interested in squeezing the last drop of performance
|
||
out of their machine may wish to avoid the trap overhead, but this is
|
||
far more trouble than it's worth: you then have to compile
|
||
*everything* this way, including the compiler's internal libraries
|
||
(libgcc.a for GNU C), because the calling conventions change.
|
||
|
||
|
||
1.12. When compiling GNU libc I get lots of errors saying functions
|
||
in glibc are duplicated in libgcc.
|
||
|
||
{EY} This is *exactly* the same problem that I was having. The problem was
|
||
due to the fact that configure didn't correctly detect that the linker flag
|
||
--no-whole-archive was supported in my linker. In my case it was because I
|
||
had run ./configure with bogus CFLAGS, and the test failed.
|
||
|
||
One thing that is particularly annoying about this problem is that once this
|
||
is misdetected, running configure again won't fix it unless you first delete
|
||
config.cache.
|
||
|
||
{UD} Starting with glibc-2.0.3 there should be a better test to avoid some
|
||
problems of this kind. The setting of CFLAGS is checked at the very
|
||
beginning and if it is not usable `configure' will bark.
|
||
|
||
|
||
1.13. Why do I get messages about missing thread functions when I use
|
||
librt? I don't even use threads.
|
||
|
||
{UD} In this case you probably mixed up your installation. librt uses
|
||
threads internally and has implicit references to the thread library.
|
||
Normally these references are satisfied automatically but if the thread
|
||
library is not in the expected place you must tell the linker where it is.
|
||
When using GNU ld it works like this:
|
||
|
||
gcc -o foo foo.c -Wl,-rpath-link=/some/other/dir -lrt
|
||
|
||
The `/some/other/dir' should contain the thread library. `ld' will use the
|
||
given path to find the implicitly referenced library while not disturbing
|
||
any other link path.
|
||
|
||
|
||
1.14. What's the problem with configure --enable-omitfp?
|
||
|
||
{AJ} When --enable-omitfp is set the libraries are built without frame
|
||
pointers. Some compilers produce buggy code for this model and therefore we
|
||
don't advise using it at the moment.
|
||
|
||
If you use --enable-omitfp, you're on your own. If you encounter problems
|
||
with a library that was build this way, we advise you to rebuild the library
|
||
without --enable-omitfp. If the problem vanishes consider tracking the
|
||
problem down and report it as compiler failure.
|
||
|
||
Since a library build with --enable-omitfp is undebuggable on most systems,
|
||
debuggable libraries are also built - you can use it by appending "_g" to
|
||
the library names.
|
||
|
||
The compilation of these extra libraries and the compiler optimizations slow
|
||
down the build process and need more disk space.
|
||
|
||
|
||
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
|
||
|
||
2. Installation and configuration issues
|
||
|
||
2.1. Can I replace the libc on my Linux system with GNU libc?
|
||
|
||
{UD} You cannot replace any existing libc for Linux with GNU libc. It is
|
||
binary incompatible and therefore has a different major version. You can,
|
||
however, install it alongside your existing libc.
|
||
|
||
For Linux there are three major libc versions:
|
||
libc-4 a.out libc
|
||
libc-5 original ELF libc
|
||
libc-6 GNU libc
|
||
|
||
You can have any combination of these three installed. For more information
|
||
consult documentation for shared library handling. The Makefiles of GNU
|
||
libc will automatically generate the needed symbolic links which the linker
|
||
will use.
|
||
|
||
|
||
2.2. How do I configure GNU libc so that the essential libraries
|
||
like libc.so go into /lib and the other into /usr/lib?
|
||
|
||
{UD,AJ} Like all other GNU packages GNU libc is designed to use a base
|
||
directory and install all files relative to this. The default is
|
||
/usr/local, because this is safe (it will not damage the system if installed
|
||
there). If you wish to install GNU libc as the primary C library on your
|
||
system, set the base directory to /usr (i.e. run configure --prefix=/usr
|
||
<other_options>). Note that this can damage your system; see question 2.3 for
|
||
details.
|
||
|
||
Some systems like Linux have a filesystem standard which makes a difference
|
||
between essential libraries and others. Essential libraries are placed in
|
||
/lib because this directory is required to be located on the same disk
|
||
partition as /. The /usr subtree might be found on another
|
||
partition/disk. If you configure for Linux with --prefix=/usr, then this
|
||
will be done automatically.
|
||
|
||
To install the essential libraries which come with GNU libc in /lib on
|
||
systems other than Linux one must explicitly request it. Autoconf has no
|
||
option for this so you have to use a `configparms' file (see the `INSTALL'
|
||
file for details). It should contain:
|
||
|
||
slibdir=/lib
|
||
sysconfdir=/etc
|
||
|
||
The first line specifies the directory for the essential libraries, the
|
||
second line the directory for system configuration files.
|
||
|
||
|
||
2.3. How should I avoid damaging my system when I install GNU libc?
|
||
|
||
{ZW} If you wish to be cautious, do not configure with --prefix=/usr. If
|
||
you don't specify a prefix, glibc will be installed in /usr/local, where it
|
||
will probably not break anything. (If you wish to be certain, set the
|
||
prefix to something like /usr/local/glibc2 which is not used for anything.)
|
||
|
||
The dangers when installing glibc in /usr are twofold:
|
||
|
||
* glibc will overwrite the headers in /usr/include. Other C libraries
|
||
install a different but overlapping set of headers there, so the
|
||
effect will probably be that you can't compile anything. You need to
|
||
rename /usr/include out of the way first. (Do not throw it away; you
|
||
will then lose the ability to compile programs against your old libc.)
|
||
|
||
* None of your old libraries, static or shared, can be used with a
|
||
different C library major version. For shared libraries this is not a
|
||
problem, because the filenames are different and the dynamic linker
|
||
will enforce the restriction. But static libraries have no version
|
||
information. You have to evacuate all the static libraries in
|
||
/usr/lib to a safe location.
|
||
|
||
The situation is rather similar to the move from a.out to ELF which
|
||
long-time Linux users will remember.
|
||
|
||
|
||
2.4. Do I need to use GNU CC to compile programs that will use the
|
||
GNU C Library?
|
||
|
||
{ZW} In theory, no; the linker does not care, and the headers are supposed
|
||
to check for GNU CC before using its extensions to the C language.
|
||
|
||
However, there are currently no ports of glibc to systems where another
|
||
compiler is the default, so no one has tested the headers extensively
|
||
against another compiler. You may therefore encounter difficulties. If you
|
||
do, please report them as bugs.
|
||
|
||
Also, in several places GNU extensions provide large benefits in code
|
||
quality. For example, the library has hand-optimized, inline assembly
|
||
versions of some string functions. These can only be used with GCC. See
|
||
question 3.8 for details.
|
||
|
||
|
||
2.5. When linking with the new libc I get unresolved symbols
|
||
`crypt' and `setkey'. Why aren't these functions in the
|
||
libc anymore?
|
||
|
||
{UD} The US places restrictions on exporting cryptographic programs and
|
||
source code. Until this law gets abolished we cannot ship the cryptographic
|
||
functions together with glibc.
|
||
|
||
The functions are available, as an add-on (see question 1.10). People in the US
|
||
may get it from the same place they got GNU libc from. People outside the
|
||
US should get the code from ftp://ftp.ifi.uio.no/pub/gnu, or another archive
|
||
site outside the USA. The README explains how to install the sources.
|
||
|
||
If you already have the crypt code on your system the reason for the failure
|
||
is probably that you did not link with -lcrypt. The crypto functions are in
|
||
a separate library to make it possible to export GNU libc binaries from the
|
||
US.
|
||
|
||
|
||
2.6. When I use GNU libc on my Linux system by linking against
|
||
the libc.so which comes with glibc all I get is a core dump.
|
||
|
||
{UD} On Linux, gcc sets the dynamic linker to /lib/ld-linux.so.1 unless the
|
||
user specifies a -dynamic-linker argument. This is the name of the libc5
|
||
dynamic linker, which does not work with glibc.
|
||
|
||
For casual use of GNU libc you can just specify
|
||
-dynamic-linker=/lib/ld-linux.so.2
|
||
|
||
which is the glibc dynamic linker, on Linux systems. On other systems the
|
||
name is /lib/ld.so.1.
|
||
|
||
To change your environment to use GNU libc for compiling you need to change
|
||
the `specs' file of your gcc. This file is normally found at
|
||
|
||
/usr/lib/gcc-lib/<arch>/<version>/specs
|
||
|
||
In this file you have to change a few things:
|
||
|
||
- change `ld-linux.so.1' to `ld-linux.so.2'
|
||
|
||
- remove all expression `%{...:-lgmon}'; there is no libgmon in glibc
|
||
|
||
- fix a minor bug by changing %{pipe:-} to %|
|
||
|
||
Here is what the gcc-2.7.2 specs file should look like when GNU libc is
|
||
installed at /usr:
|
||
|
||
-----------------------------------------------------------------------
|
||
*asm:
|
||
%{V} %{v:%{!V:-V}} %{Qy:} %{!Qn:-Qy} %{n} %{T} %{Ym,*} %{Yd,*} %{Wa,*:%*}
|
||
|
||
*asm_final:
|
||
%|
|
||
|
||
*cpp:
|
||
%{fPIC:-D__PIC__ -D__pic__} %{fpic:-D__PIC__ -D__pic__} %{!m386:-D__i486__} %{posix:-D_POSIX_SOURCE} %{pthread:-D_REENTRANT}
|
||
|
||
*cc1:
|
||
%{profile:-p}
|
||
|
||
*cc1plus:
|
||
|
||
|
||
*endfile:
|
||
%{!shared:crtend.o%s} %{shared:crtendS.o%s} crtn.o%s
|
||
|
||
*link:
|
||
-m elf_i386 %{shared:-shared} %{!shared: %{!ibcs: %{!static: %{rdynamic:-export-dynamic} %{!dynamic-linker:-dynamic-linker /lib/ld-linux.so.2}} %{static:-static}}}
|
||
|
||
*lib:
|
||
%{!shared: %{pthread:-lpthread} %{profile:-lc_p} %{!profile: -lc}}
|
||
|
||
*libgcc:
|
||
-lgcc
|
||
|
||
*startfile:
|
||
%{!shared: %{pg:gcrt1.o%s} %{!pg:%{p:gcrt1.o%s} %{!p:%{profile:gcrt1.o%s} %{!profile:crt1.o%s}}}} crti.o%s %{!shared:crtbegin.o%s} %{shared:crtbeginS.o%s}
|
||
|
||
*switches_need_spaces:
|
||
|
||
|
||
*signed_char:
|
||
%{funsigned-char:-D__CHAR_UNSIGNED__}
|
||
|
||
*predefines:
|
||
-D__ELF__ -Dunix -Di386 -Dlinux -Asystem(unix) -Asystem(posix) -Acpu(i386) -Amachine(i386)
|
||
|
||
*cross_compile:
|
||
0
|
||
|
||
*multilib:
|
||
. ;
|
||
|
||
-----------------------------------------------------------------------
|
||
|
||
Things get a bit more complicated if you have GNU libc installed in some
|
||
other place than /usr, i.e., if you do not want to use it instead of the old
|
||
libc. In this case the needed startup files and libraries are not found in
|
||
the regular places. So the specs file must tell the compiler and linker
|
||
exactly what to use.
|
||
|
||
Version 2.7.2.3 does and future versions of GCC will automatically
|
||
provide the correct specs.
|
||
|
||
|
||
2.7. Looking through the shared libc file I haven't found the
|
||
functions `stat', `lstat', `fstat', and `mknod' and while
|
||
linking on my Linux system I get error messages. How is
|
||
this supposed to work?
|
||
|
||
{RM} Believe it or not, stat and lstat (and fstat, and mknod) are supposed
|
||
to be undefined references in libc.so.6! Your problem is probably a missing
|
||
or incorrect /usr/lib/libc.so file; note that this is a small text file now,
|
||
not a symlink to libc.so.6. It should look something like this:
|
||
|
||
GROUP ( libc.so.6 libc_nonshared.a )
|
||
|
||
|
||
2.8. How can I compile gcc 2.7.2.1 from the gcc source code using
|
||
glibc 2.x?
|
||
|
||
{AJ} There's only correct support for glibc 2.0.x in gcc 2.7.2.3 or later.
|
||
But you should get at least gcc 2.8.1 or egcs 1.0.2 (or later versions)
|
||
instead.
|
||
|
||
|
||
2.9. The `gencat' utility cannot process the catalog sources which
|
||
were used on my Linux libc5 based system. Why?
|
||
|
||
{UD} The `gencat' utility provided with glibc complies to the XPG standard.
|
||
The older Linux version did not obey the standard, so they are not
|
||
compatible.
|
||
|
||
To ease the transition from the Linux version some of the non-standard
|
||
features are also present in the `gencat' program of GNU libc. This mainly
|
||
includes the use of symbols for the message number and the automatic
|
||
generation of header files which contain the needed #defines to map the
|
||
symbols to integers.
|
||
|
||
Here is a simple SED script to convert at least some Linux specific catalog
|
||
files to the XPG4 form:
|
||
|
||
-----------------------------------------------------------------------
|
||
# Change catalog source in Linux specific format to standard XPG format.
|
||
# Ulrich Drepper <drepper@cygnus.com>, 1996.
|
||
#
|
||
/^\$ #/ {
|
||
h
|
||
s/\$ #\([^ ]*\).*/\1/
|
||
x
|
||
s/\$ #[^ ]* *\(.*\)/\$ \1/
|
||
}
|
||
|
||
/^# / {
|
||
s/^# \(.*\)/\1/
|
||
G
|
||
s/\(.*\)\n\(.*\)/\2 \1/
|
||
}
|
||
-----------------------------------------------------------------------
|
||
|
||
|
||
2.10. Programs using libc have their messages translated, but other
|
||
behavior is not localized (e.g. collating order); why?
|
||
|
||
{ZW} Translated messages are automatically installed, but the locale
|
||
database that controls other behaviors is not. You need to run localedef to
|
||
install this database, after you have run `make install'. For example, to
|
||
set up the French Canadian locale, simply issue the command
|
||
|
||
localedef -i fr_CA -f ISO-8859-1 fr_CA
|
||
|
||
Please see localedata/README in the source tree for further details.
|
||
|
||
|
||
2.11. I have set up /etc/nis.conf, and the Linux libc 5 with NYS
|
||
works great. But the glibc NIS+ doesn't seem to work.
|
||
|
||
{TK} The glibc NIS+ implementation uses a /var/nis/NIS_COLD_START file for
|
||
storing information about the NIS+ server and their public keys, because the
|
||
nis.conf file does not contain all the necessary information. You have to
|
||
copy a NIS_COLD_START file from a Solaris client (the NIS_COLD_START file is
|
||
byte order independent) or generate it with nisinit from the nis-tools
|
||
package; available at
|
||
|
||
http://www-vt.uni-paderborn.de/~kukuk/linux/nisplus.html
|
||
|
||
|
||
2.12. I have killed ypbind to stop using NIS, but glibc
|
||
continues using NIS.
|
||
|
||
{TK} For faster NIS lookups, glibc uses the /var/yp/binding/ files from
|
||
ypbind. ypbind 3.3 and older versions don't always remove these files, so
|
||
glibc will continue to use them. Other BSD versions seem to work correctly.
|
||
Until ypbind 3.4 is released, you can find a patch at
|
||
|
||
ftp://ftp.kernel.org/pub/linux/utils/net/NIS/ypbind-3.3-glibc3.diff.
|
||
|
||
|
||
2.13. Under Linux/Alpha, I always get "do_ypcall: clnt_call:
|
||
RPC: Unable to receive; errno = Connection refused" when using NIS.
|
||
|
||
{TK} You need a ypbind version which is 64bit clean. Some versions are not
|
||
64bit clean. A 64bit clean implementation is ypbind-mt. For ypbind 3.3,
|
||
you need the patch from ftp.kernel.org (See the previous question). I don't
|
||
know about other versions.
|
||
|
||
|
||
2.14. After installing glibc name resolving doesn't work properly.
|
||
|
||
{AJ} You probably should read the manual section describing nsswitch.conf
|
||
(just type `info libc "NSS Configuration File"'). The NSS configuration
|
||
file is usually the culprit.
|
||
|
||
|
||
2.15. How do I create the databases for NSS?
|
||
|
||
{AJ} If you have an entry "db" in /etc/nsswitch.conf you should also create
|
||
the database files. The glibc sources contain a Makefile which does the
|
||
neccessary conversion and calls to create those files. The file is
|
||
`db-Makefile' in the subdirectory `nss' and you can call it with `make -f
|
||
db-Makefile'. Please note that not all services are capable of using a
|
||
database. Currently passwd, group, ethers, protocol, rpc, services shadow
|
||
and netgroup are implemented.
|
||
|
||
|
||
2.16. I have /usr/include/net and /usr/include/scsi as symlinks
|
||
into my Linux source tree. Is that wrong?
|
||
|
||
{PB} This was necessary for libc5, but is not correct when using glibc.
|
||
Including the kernel header files directly in user programs usually does not
|
||
work (see question 3.5). glibc provides its own <net/*> and <scsi/*> header
|
||
files to replace them, and you may have to remove any symlink that you have
|
||
in place before you install glibc. However, /usr/include/asm and
|
||
/usr/include/linux should remain as they were.
|
||
|
||
|
||
2.17. Programs like `logname', `top', `uptime' `users', `w' and
|
||
`who', show incorrect information about the (number of)
|
||
users on my system. Why?
|
||
|
||
{MK} See question 3.2.
|
||
|
||
|
||
2.18. After upgrading to glibc 2.1 with symbol versioning I get
|
||
errors about undefined symbols. What went wrong?
|
||
|
||
{AJ} The problem is caused either by wrong program code or tools. In the
|
||
versioned libc a lot of symbols are now local that were global symbols in
|
||
previous versions. It seems that programs linked against older versions
|
||
often accidentally used libc global variables -- something that should not
|
||
happen.
|
||
|
||
The only way to fix this is to recompile your program. Sorry, that's the
|
||
price you might have to pay once for quite a number of advantages with
|
||
symbol versioning.
|
||
|
||
|
||
2.19. When I start the program XXX after upgrading the library
|
||
I get
|
||
XXX: Symbol `_sys_errlist' has different size in shared
|
||
object, consider re-linking
|
||
Why? What should I do?
|
||
|
||
{UD} As the message says, relink the binary. The problem is that a few
|
||
symbols from the library can change in size and there is no way to avoid
|
||
this. _sys_errlist is a good example. Occasionally there are new error
|
||
numbers added to the kernel and this must be reflected at user level,
|
||
breaking programs that refer to them directly.
|
||
|
||
Such symbols should normally not be used at all. There are mechanisms to
|
||
avoid using them. In the case of _sys_errlist, there is the strerror()
|
||
function which should _always_ be used instead. So the correct fix is to
|
||
rewrite that part of the application.
|
||
|
||
In some situations (especially when testing a new library release) it might
|
||
be possible that a symbol changed size when that should not have happened.
|
||
So in case of doubt report such a warning message as a problem.
|
||
|
||
|
||
2.20. What do I need for C++ development?
|
||
|
||
{HJ,AJ} You need either egcs 1.0.2 or gcc-2.8.1 with libstdc++ 2.8.1 (or
|
||
more recent versions). libg++ 2.7.2 (and the Linux Versions 2.7.2.x) doesn't
|
||
work very well with the GNU C library due to vtable thunks. If you're
|
||
upgrading from glibc 2.0.x to 2.1 you have to recompile libstdc++ since the
|
||
library compiled for 2.0 is not compatible due to the new Large File Support
|
||
(LFS) in version 2.1.
|
||
|
||
|
||
2.21. Even statically linked programs need some shared libraries
|
||
which is not acceptable for me. What can I do?
|
||
|
||
{AJ} NSS (for details just type `info libc "Name Service Switch"') won't
|
||
work properly without shared libraries. NSS allows using different services
|
||
(e.g. NIS, files, db, hesiod) by just changing one configuration file
|
||
(/etc/nsswitch.conf) without relinking any programs. The only disadvantage
|
||
is that now static libraries need to access shared libraries. This is
|
||
handled transparently by the GNU C library.
|
||
|
||
A solution is to configure glibc with --enable-static-nss. In this case you
|
||
can create a static binary that will use only the services dns and files
|
||
(change /etc/nsswitch.conf for this). You need to link explicitly against
|
||
all these services. For example:
|
||
|
||
gcc -static test-netdb.c -o test-netdb.c \
|
||
-lc -lnss_files -lnss_dns -lresolv
|
||
|
||
The problem with this approach is that you've got to link every static
|
||
program that uses NSS routines with all those libraries.
|
||
|
||
{UD} In fact, one cannot say anymore that a libc compiled with this
|
||
option is using NSS. There is no switch anymore. Therefore it is
|
||
*highly* recommended *not* to use --enable-static-nss since this makes
|
||
the behaviour of the programs on the system inconsistent.
|
||
|
||
|
||
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
|
||
|
||
3. Source and binary incompatibilities, and what to do about them
|
||
|
||
3.1. I expect GNU libc to be 100% source code compatible with
|
||
the old Linux based GNU libc. Why isn't it like this?
|
||
|
||
{DMT,UD} Not every extension in Linux libc's history was well thought-out.
|
||
In fact it had a lot of problems with standards compliance and with
|
||
cleanliness. With the introduction of a new version number these errors can
|
||
now be corrected. Here is a list of the known source code
|
||
incompatibilities:
|
||
|
||
* _GNU_SOURCE: glibc does not make the GNU extensions available
|
||
automatically. If a program depends on GNU extensions or some
|
||
other non-standard functionality, it is necessary to compile it
|
||
with the C compiler option -D_GNU_SOURCE, or better, to put
|
||
`#define _GNU_SOURCE' at the beginning of your source files, before
|
||
any C library header files are included. This difference normally
|
||
manifests itself in the form of missing prototypes and/or data type
|
||
definitions. Thus, if you get such errors, the first thing you
|
||
should do is try defining _GNU_SOURCE and see if that makes the
|
||
problem go away.
|
||
|
||
For more information consult the file `NOTES' in the GNU C library
|
||
sources.
|
||
|
||
* reboot(): GNU libc sanitizes the interface of reboot() to be more
|
||
compatible with the interface used on other OSes. reboot() as
|
||
implemented in glibc takes just one argument. This argument
|
||
corresponds to the third argument of the Linux reboot system call.
|
||
That is, a call of the form reboot(a, b, c) needs to be changed into
|
||
reboot(c). Beside this the header <sys/reboot.h> defines the needed
|
||
constants for the argument. These RB_* constants should be used
|
||
instead of the cryptic magic numbers.
|
||
|
||
* swapon(): the interface of this function didn't change, but the
|
||
prototype is in a separate header file <sys/swap.h>. This header
|
||
file also provides the SWAP_* constants defined by <linux/swap.h>;
|
||
you should use them for the second argument to swapon().
|
||
|
||
* errno: If a program uses the variable "errno", then it _must_
|
||
include <errno.h>. The old libc often (erroneously) declared this
|
||
variable implicitly as a side-effect of including other libc header
|
||
files. glibc is careful to avoid such namespace pollution, which,
|
||
in turn, means that you really need to include the header files that
|
||
you depend on. This difference normally manifests itself in the
|
||
form of the compiler complaining about references to an undeclared
|
||
symbol "errno".
|
||
|
||
* Linux-specific syscalls: All Linux system calls now have appropriate
|
||
library wrappers and corresponding declarations in various header files.
|
||
This is because the syscall() macro that was traditionally used to
|
||
work around missing syscall wrappers are inherently non-portable and
|
||
error-prone. The following table lists all the new syscall stubs,
|
||
the header-file declaring their interface and the system call name.
|
||
|
||
syscall name: wrapper name: declaring header file:
|
||
------------- ------------- ----------------------
|
||
bdflush bdflush <sys/kdaemon.h>
|
||
syslog ksyslog_ctl <sys/klog.h>
|
||
|
||
* lpd: Older versions of lpd depend on a routine called _validuser().
|
||
The library does not provide this function, but instead provides
|
||
__ivaliduser() which has a slightly different interface. Simply
|
||
upgrading to a newer lpd should fix this problem (e.g., the 4.4BSD
|
||
lpd is known to be working).
|
||
|
||
* resolver functions/BIND: like on many other systems the functions of
|
||
the resolver library are not included in libc itself. There is a
|
||
separate library libresolv. If you get undefined symbol errors for
|
||
symbols starting with `res_*' simply add -lresolv to your linker
|
||
command line.
|
||
|
||
* the `signal' function's behavior corresponds to the BSD semantic and
|
||
not the SysV semantic as it was in libc-5. The interface on all GNU
|
||
systems shall be the same and BSD is the semantic of choice. To use
|
||
the SysV behavior simply use `sysv_signal', or define _XOPEN_SOURCE.
|
||
See question 3.7 for details.
|
||
|
||
|
||
3.2. Why does getlogin() always return NULL on my Linux box?
|
||
|
||
{UD} The GNU C library has a format for the UTMP and WTMP file which differs
|
||
from what your system currently has. It was extended to fulfill the needs
|
||
of the next years when IPv6 is introduced. The record size is different and
|
||
some fields have different positions. The files written by functions from
|
||
the one library cannot be read by functions from the other library. Sorry,
|
||
but this is what a major release is for. It's better to have a cut now than
|
||
having no means to support the new techniques later.
|
||
|
||
{MK} There is however a (partial) solution for this problem. Please take a
|
||
look at the file `login/README.utmpd'.
|
||
|
||
|
||
3.3. Where are the DST_* constants found in <sys/time.h> on many
|
||
systems?
|
||
|
||
{UD} These constants come from the old BSD days and are not used anymore
|
||
(libc5 does not actually implement the handling although the constants are
|
||
defined).
|
||
|
||
Instead GNU libc contains zone database support and compatibility code for
|
||
POSIX TZ environment variable handling.
|
||
|
||
|
||
3.4. The prototypes for `connect', `accept', `getsockopt',
|
||
`setsockopt', `getsockname', `getpeername', `send',
|
||
`sendto', and `recvfrom' are different in GNU libc from
|
||
any other system I saw. This is a bug, isn't it?
|
||
|
||
{UD} No, this is no bug. This version of GNU libc already follows the new
|
||
Single Unix specifications (and I think the POSIX.1g draft which adopted the
|
||
solution). The type for a parameter describing a size is now `socklen_t', a
|
||
new type.
|
||
|
||
|
||
3.5. On Linux I've got problems with the declarations in Linux
|
||
kernel headers.
|
||
|
||
{UD,AJ} On Linux, the use of kernel headers is reduced to the minimum. This
|
||
gives Linus the ability to change the headers more freely. Also, user
|
||
programs are now insulated from changes in the size of kernel data
|
||
structures.
|
||
|
||
For example, the sigset_t type is 32 or 64 bits wide in the kernel. In
|
||
glibc it is 1024 bits wide. This guarantees that when the kernel gets a
|
||
bigger sigset_t (for POSIX.1e realtime support, say) user programs will not
|
||
have to be recompiled. Consult the header files for more information about
|
||
the changes.
|
||
|
||
Therefore you shouldn't include Linux kernel header files directly if glibc
|
||
has defined a replacement. Otherwise you might get undefined results because
|
||
of type conflicts.
|
||
|
||
|
||
3.6. I don't include any kernel headers myself but the compiler
|
||
still complains about redeclarations of types in the kernel
|
||
headers.
|
||
|
||
{UD} The kernel headers before Linux 2.1.61 and 2.0.32 don't work correctly
|
||
with glibc. Compiling C programs is possible in most cases but C++ programs
|
||
have (due to the change of the name lookups for `struct's) problems. One
|
||
prominent example is `struct fd_set'.
|
||
|
||
There might be some problems left but 2.1.61/2.0.32 fix most of the known
|
||
ones. See the BUGS file for other known problems.
|
||
|
||
|
||
3.7. Why don't signals interrupt system calls anymore?
|
||
|
||
{ZW} By default GNU libc uses the BSD semantics for signal(), unlike Linux
|
||
libc 5 which used System V semantics. This is partially for compatibility
|
||
with other systems and partially because the BSD semantics tend to make
|
||
programming with signals easier.
|
||
|
||
There are three differences:
|
||
|
||
* BSD-style signals that occur in the middle of a system call do not
|
||
affect the system call; System V signals cause the system call to
|
||
fail and set errno to EINTR.
|
||
|
||
* BSD signal handlers remain installed once triggered. System V signal
|
||
handlers work only once, so one must reinstall them each time.
|
||
|
||
* A BSD signal is blocked during the execution of its handler. In other
|
||
words, a handler for SIGCHLD (for example) does not need to worry about
|
||
being interrupted by another SIGCHLD. It may, however, be interrupted
|
||
by other signals.
|
||
|
||
There is general consensus that for `casual' programming with signals, the
|
||
BSD semantics are preferable. You don't need to worry about system calls
|
||
returning EINTR, and you don't need to worry about the race conditions
|
||
associated with one-shot signal handlers.
|
||
|
||
If you are porting an old program that relies on the old semantics, you can
|
||
quickly fix the problem by changing signal() to sysv_signal() throughout.
|
||
Alternatively, define _XOPEN_SOURCE before including <signal.h>.
|
||
|
||
For new programs, the sigaction() function allows you to specify precisely
|
||
how you want your signals to behave. All three differences listed above are
|
||
individually switchable on a per-signal basis with this function.
|
||
|
||
If all you want is for one specific signal to cause system calls to fail and
|
||
return EINTR (for example, to implement a timeout) you can do this with
|
||
siginterrupt().
|
||
|
||
|
||
3.8. I've got errors compiling code that uses certain string
|
||
functions. Why?
|
||
|
||
{AJ} glibc 2.1 has special string functions that are faster than the normal
|
||
library functions. Some of the functions are additionally implemented as
|
||
inline functions and others as macros.
|
||
|
||
The optimized string functions are only used when compiling with
|
||
optimizations (-O1 or higher). The behavior can be changed with two feature
|
||
macros:
|
||
|
||
* __NO_STRING_INLINES: Don't do any string optimizations.
|
||
* __USE_STRING_INLINES: Use assembly language inline functions (might
|
||
increase code size dramatically).
|
||
|
||
Since some of these string functions are now additionally defined as macros,
|
||
code like "char *strncpy();" doesn't work anymore (and is unnecessary, since
|
||
<string.h> has the necessary declarations). Either change your code or
|
||
define __NO_STRING_INLINES.
|
||
|
||
{UD} Another problem in this area is that gcc still has problems on machines
|
||
with very few registers (e.g., ix86). The inline assembler code can require
|
||
almost all the registers and the register allocator cannot always handle
|
||
this situation.
|
||
|
||
One can disable the string optimizations selectively. Instead of writing
|
||
|
||
cp = strcpy (foo, "lkj");
|
||
|
||
one can write
|
||
|
||
cp = (strcpy) (foo, "lkj");
|
||
|
||
This disables the optimization for that specific call.
|
||
|
||
|
||
3.9. I get compiler messages "Initializer element not constant" with
|
||
stdin/stdout/stderr. Why?
|
||
|
||
{RM,AJ} Constructs like:
|
||
static FILE *InPtr = stdin;
|
||
|
||
lead to this message. This is correct behaviour with glibc since stdin is
|
||
not a constant expression. Please note that a strict reading of ISO C does
|
||
not allow above constructs.
|
||
|
||
One of the advantages of this is that you can assign to stdin, stdout, and
|
||
stderr just like any other global variable (e.g. `stdout = my_stream;'),
|
||
which can be very useful with custom streams that you can write with libio
|
||
(but beware this is not necessarily portable). The reason to implement it
|
||
this way were versioning problems with the size of the FILE structure.
|
||
|
||
|
||
3.10. I can't compile with gcc -traditional (or
|
||
-traditional-cpp). Why?
|
||
|
||
{AJ} glibc2 does break -traditional and -traditonal-cpp - and will continue
|
||
to do so. For example constructs of the form:
|
||
|
||
enum {foo
|
||
#define foo foo
|
||
}
|
||
|
||
are useful for debugging purposes (you can use foo with your debugger that's
|
||
why we need the enum) and for compatibility (other systems use defines and
|
||
check with #ifdef).
|
||
|
||
|
||
3.11. I get some errors with `gcc -ansi'. Isn't glibc ANSI compatible?
|
||
|
||
{AJ} The GNU C library is compatible with the ANSI/ISO C standard. If
|
||
you're using `gcc -ansi', the glibc includes which are specified in the
|
||
standard follow the standard. The ANSI/ISO C standard defines what has to be
|
||
in the include files - and also states that nothing else should be in the
|
||
include files (btw. you can still enable additional standards with feature
|
||
flags).
|
||
|
||
The GNU C library is conforming to ANSI/ISO C - if and only if you're only
|
||
using the headers and library functions defined in the standard.
|
||
|
||
|
||
3.12. I can't access some functions anymore. nm shows that they do
|
||
exist but linking fails nevertheless.
|
||
|
||
{AJ} With the introduction of versioning in glibc 2.1 it is possible to
|
||
export only those identifiers (functions, variables) that are really needed
|
||
by application programs and by other parts of glibc. This way a lot of
|
||
internal interfaces are now hidden. nm will still show those identifiers
|
||
but marking them as internal. ISO C states that identifiers beginning with
|
||
an underscore are internal to the libc. An application program normally
|
||
shouldn't use those internal interfaces (there are exceptions,
|
||
e.g. __ivaliduser). If a program uses these interfaces, it's broken. These
|
||
internal interfaces might change between glibc releases or dropped
|
||
completely.
|
||
|
||
|
||
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
|
||
|
||
4. Miscellaneous
|
||
|
||
4.1. After I changed configure.in I get `Autoconf version X.Y.
|
||
or higher is required for this script'. What can I do?
|
||
|
||
{UD} You have to get the specified autoconf version (or a later one)
|
||
from your favorite mirror of ftp.gnu.org.
|
||
|
||
|
||
4.2. When I try to compile code which uses IPv6 headers and
|
||
definitions on my Linux 2.x.y system I am in trouble.
|
||
Nothing seems to work.
|
||
|
||
{UD} The problem is that IPv6 development still has not reached a point
|
||
where the headers are stable. There are still lots of incompatible changes
|
||
made and the libc headers have to follow.
|
||
|
||
Also, make sure you have a suitably recent kernel. As of the 970401
|
||
snapshot, according to Philip Blundell <Philip.Blundell@pobox.com>, the
|
||
required kernel version is at least 2.1.30.
|
||
|
||
|
||
4.3. When I set the timezone by setting the TZ environment variable
|
||
to EST5EDT things go wrong since glibc computes the wrong time
|
||
from this information.
|
||
|
||
{UD} The problem is that people still use the braindamaged POSIX method to
|
||
select the timezone using the TZ environment variable with a format EST5EDT
|
||
or whatever. People, read the POSIX standard, the implemented behaviour is
|
||
correct! What you see is in fact the result of the decisions made while
|
||
POSIX.1 was created. We've only implemented the handling of TZ this way to
|
||
be POSIX compliant. It is not really meant to be used.
|
||
|
||
The alternative approach to handle timezones which is implemented is the
|
||
correct one to use: use the timezone database. This avoids all the problems
|
||
the POSIX method has plus it is much easier to use. Simply run the tzselect
|
||
shell script, answer the question and use the name printed in the end by
|
||
making a symlink to /usr/share/zoneinfo/NAME (NAME is the returned value
|
||
from tzselect) from the file /etc/localtime. That's all. You never again
|
||
have to worry.
|
||
|
||
So, please avoid sending bug reports about time related problems if you use
|
||
the POSIX method and you have not verified something is really broken by
|
||
reading the POSIX standards.
|
||
|
||
|
||
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
|
||
|
||
Answers were given by:
|
||
{UD} Ulrich Drepper, <drepper@cygnus.com>
|
||
{DMT} David Mosberger-Tang, <davidm@AZStarNet.com>
|
||
{RM} Roland McGrath, <roland@gnu.org>
|
||
{AJ} Andreas Jaeger, <aj@arthur.rhein-neckar.de>
|
||
{EY} Eric Youngdale, <eric@andante.jic.com>
|
||
{PB} Phil Blundell, <Philip.Blundell@pobox.com>
|
||
{MK} Mark Kettenis, <kettenis@phys.uva.nl>
|
||
{ZW} Zack Weinberg, <zack@rabi.phys.columbia.edu>
|
||
{TK} Thorsten Kukuk, <kukuk@vt.uni-paderborn.de>
|
||
{GK} Geoffrey Keating, <geoffk@ozemail.com.au>
|
||
{HJ} H.J. Lu, <hjl@gnu.org>
|
||
|
||
Local Variables:
|
||
mode:outline
|
||
outline-regexp:"\\?"
|
||
fill-column:76
|
||
End:
|