Move FAQ to wiki

The FAQ is now at http://sourceware.org/glibc/wiki/FAQ and not
anymore part of the repository.

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-	    Frequently Asked Questions about the GNU C Library
-
-This document tries to answer questions a user might have when installing
-and using glibc.  Please make sure you read this before sending questions or
-bug reports to the maintainers.
-
-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.
-
-If you have any questions you think should be answered in this document,
-please let me know.
-
-						  --drepper@redhat.com
-
-? Compiling glibc
-
-??	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.
-
-The systems glibc is known to work on as of this release, and most probably
-in the future, are:
-
-	*-*-gnu			GNU Hurd
-	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
-	powerpc64-*-linux-gnu	Linux-2.4+ on 64-bit PowerPC systems
-	sparc-*-linux-gnu	Linux-2.x on SPARC
-	sparc64-*-linux-gnu	Linux-2.x on UltraSPARC
-	arm-*-none		ARM standalone systems
-	arm-*-linux		Linux-2.x on ARM
-	arm-*-linuxaout		Linux-2.x on ARM using a.out binaries
-	mips*-*-linux-gnu	Linux-2.x on MIPS
-	ia64-*-linux-gnu	Linux-2.x on ia64
-	s390-*-linux-gnu	Linux-2.x on IBM S/390
-	s390x-*-linux-gnu	Linux-2.x on IBM S/390 64-bit
-	cris-*-linux-gnu	Linux-2.4+ on CRIS
-
-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, see the GNU C Library web pages to learn
-how to start contributing:
-
-	http://www.gnu.org/software/libc/resources.html
-
-??binsize	What compiler do I need to build GNU libc?
-
-{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
-
-and the many mirror sites.  ftp.gnu.org is always overloaded, so try to find
-a local mirror first.
-
-You should always try to use the latest official release.  Older versions
-may not have all the features GNU libc requires.  The current releases of
-gcc (3.2 or newer) should work with the GNU C library (for MIPS see ?mips).
-
-Please note that gcc 2.95 and 2.95.x cannot compile glibc on Alpha due to
-problems in the complex float support.
-
-??	When I try to compile glibc I get only error messages.
-	What's wrong?
-
-{UD} You definitely need GNU make to build GNU libc.  No other make
-program has the needed functionality.
-
-We recommend version GNU make version 3.79 or newer.  Older versions have
-bugs and/or are missing features.
-
-??	Do I need a special linker or assembler?
-
-{ZW} If you want a shared library, you need a linker and assembler that
-understand all the features of ELF, including weak and versioned symbols.
-The static library can be compiled with less featureful tools, but lacks key
-features such as NSS.
-
-For Linux or Hurd, you want binutils 2.13 or higher.  These are the only
-versions we've tested and found reliable.  Other versions may work but we
-don't recommend them, especially not when C++ is involved.
-
-Other operating systems may come with system tools that have all the
-necessary features, but this is moot because glibc hasn't been ported to
-them.
-
-??powerpc	Which compiler should I use for powerpc?
-
-{} Removed.  Does not apply anymore.
-
-??arm	Which tools should I use for ARM?
-
-{} Removed.  Does not apply anymore.
-
-??	Do I need some more things to compile the 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 are built with special tools.  E.g., files ending in .gperf
-  need a `gperf' program.  The GNU version (now available in a separate
-  package, formerly only as 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.
-
-* Perl 5 is needed if you wish to test an installation of GNU libc
-  as the primary C library.
-
-* 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 (~400MB for i?86-linux; more for RISC platforms).
-
-* plenty of time.  Compiling just the shared and static libraries for
-  35mins on a 2xPIII@550Mhz w/ 512MB RAM.  On a 2xUltraSPARC-II@360Mhz
-  w/ 1GB RAM it takes about 14 minutes.  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 for
-  an earlier (and smaller!) version of glibc 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 (Motorola 68030 @ 32 Mhz, 34 Mb memory)
-
-  A full build of the PowerPC library took 1h on a PowerPC 750@400Mhz w/
-  64MB of RAM, and about 9h on a 601@60Mhz w/ 72Mb.
-
-??	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 if you used old kernel headers to compile the GNU C
-library.
-
-{ZW} Even if you are using a 2.0 kernel on your machine, we recommend you
-compile GNU libc with 2.2 kernel headers.  That way you won't have to
-recompile libc if you ever upgrade to kernel 2.2.  To tell libc which
-headers to use, give configure the --with-headers switch
-(e.g. --with-headers=/usr/src/linux-2.2.0/include).
-
-Note that you must configure the 2.2 kernel if you do this, otherwise libc
-will be unable to find <linux/version.h>.  Just change the current directory
-to the root of the 2.2 tree and do `make include/linux/version.h'.
-
-??	The compiler hangs while building iconvdata modules.  What's
-	wrong?
-
-{} Removed.  Does not apply anymore.
-
-??	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.
-
-??addon	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
-linuxthreads package.
-
-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=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.
-
-Most add-ons are tightly coupled to a specific GNU libc version.  Please
-check that the add-ons work with the GNU libc.  For example the linuxthreads
-add-on has the same numbering scheme as the libc and will in general only
-work with the corresponding libc.
-
-{AJ} With glibc 2.2 the crypt add-on and with glibc 2.1 the localedata
-add-on have been integrated into the normal glibc distribution, crypt and
-localedata are therefore not anymore add-ons.
-
-??	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.
-
-??	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.
-
-??	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.
-
-??	What's the problem with configure --enable-omitfp?
-
-{} Removed.  Does not apply anymore.
-
-??	I get failures during `make check'.  What should I do?
-
-{AJ} The testsuite should compile and run cleanly on your system; every
-failure should be looked into.  Depending on the failures, you probably
-should not install the library at all.
-
-You should consider reporting it in bugzilla
-<http://sourceware.org/bugzilla/> providing as much detail as possible.
-If you run a test directly, please remember to set up the environment
-correctly. You want to test the compiled library - and not your installed
-one. The best way is to copy the exact command line which failed and run
-the test from the subdirectory for this test in the sources.
-
-There are some failures which are not directly related to the GNU libc:
-- Some compilers produce buggy code.  No compiler gets single precision
-  complex numbers correct on Alpha.  Otherwise, gcc-3.2 should be ok.
-- The kernel might have bugs.  For example on Linux/Alpha 2.0.34 the
-  floating point handling has quite a number of bugs and therefore most of
-  the test cases in the math subdirectory will fail.  Linux 2.2 has
-  fixes for the floating point support on Alpha.  The Linux/SPARC kernel has
-  also some bugs in the FPU emulation code (as of Linux 2.2.0).
-- Other tools might have problems.  For example bash 2.03 gives a
-  segmentation fault running the tst-rpmatch.sh test script.
-
-??	What is symbol versioning good for?  Do I need it?
-
-{AJ} Symbol versioning solves problems that are related to interface
-changes.  One version of an interface might have been introduced in a
-previous version of the GNU C library but the interface or the semantics of
-the function has been changed in the meantime.  For binary compatibility
-with the old library, a newer library needs to still have the old interface
-for old programs.  On the other hand, new programs should use the new
-interface.  Symbol versioning is the solution for this problem.  The GNU
-libc version 2.1 uses symbol versioning by default if the installed binutils
-supports it.
-
-We don't advise building without symbol versioning, since you lose binary
-compatibility - forever!  The binary compatibility you lose is not only
-against the previous version of the GNU libc (version 2.0) but also against
-all future versions.
-
-?? 	How can I compile on my fast ix86 machine a working libc for my slow
-	i386?  After installing libc, programs abort with "Illegal
-	Instruction".
-
-{AJ} glibc and gcc might generate some instructions on your machine that
-aren't available on i386.  You've got to tell glibc that you're configuring
-for i386 with adding i386 as your machine, for example:
-
-	../configure --prefix=/usr i386-pc-linux-gnu
-
-And you need to tell gcc to only generate i386 code, just add `-mcpu=i386'
-(just -m386 doesn't work) to your CFLAGS.
-
-{UD} This applies not only to the i386.  Compiling on a i686 for any older
-model will also fail if the above  methods are not used.
-
-??	`make' complains about a missing dlfcn/libdl.so when building
-	malloc/libmemprof.so.  How can I fix this?
-
-{AJ} Older make version (<= 3.78.90) have a bug which was hidden by a bug in
-glibc (<= 2.1.2).  You need to upgrade make to a newer or fixed version.
-
-After upgrading make, you should remove the file sysd-sorted in your build
-directory.  The problem is that the broken make creates a wrong order for
-one list in that file.  The list has to be recreated with the new make -
-which happens if you remove the file.
-
-You might encounter this bug also in other situations where make scans
-directories.  I strongly advise to upgrade your make version to 3.79 or
-newer.
-
-
-??mips	Which tools should I use for MIPS?
-
-{AJ} You should use the current development version of gcc 3.2 or newer from
-CVS.
-
-You need also recent binutils, anything before and including 2.11 will not
-work correctly.  Either try the Linux binutils 2.11.90.0.5 from HJ Lu or the
-current development version of binutils from CVS.
-
-Please note that `make check' might fail for a number of the math tests
-because of problems of the FPU emulation in the Linux kernel (the MIPS FPU
-doesn't handle all cases and needs help from the kernel).
-
-
-??powerpc64	Which compiler should I use for powerpc64?
-
-{SM} You want to use at least gcc 3.2 (together with the right versions
-of all the other tools, of course).
-
-??	`make' fails when running rpcgen the first time,
-	what is going on? How do I fix this?
-
-{CO} The first invocation of rpcgen is also the first use of the recently
-compiled dynamic loader.  If there is any problem with the dynamic loader
-it will more than likely fail to run rpcgen properly. This could be due to
-any number of problems.
-
-The only real solution is to debug the loader and determine the problem
-yourself. Please remember that for each architecture there may be various
-patches required to get glibc HEAD into a runnable state. The best course
-of action is to determine if you have all the required patches.
-
-??	Why do I get:
-	`#error "glibc cannot be compiled without optimization"',
-	when trying to compile GNU libc with GNU CC?
-
-{AJ,CO} There are a couple of reasons why the GNU C library will not work
-correctly if it is not complied with optimzation.
-
-In the early startup of the dynamic loader (_dl_start), before
-relocation of the PLT, you cannot make function calls. You must inline
-the functions you will use during early startup, or call compiler
-builtins (__builtin_*).
-
-Without optimizations enabled GNU CC will not inline functions. The
-early startup of the dynamic loader will make function calls via an
-unrelocated PLT and crash.
-
-Without auditing the dynamic linker code it would be difficult to remove
-this requirement.
-
-Another reason is that nested functions must be inlined in many cases to
-avoid executable stacks.
-
-In practice there is no reason to compile without optimizations, therefore
-we require that GNU libc be compiled with optimizations enabled.
-
-? Installation and configuration issues
-
-??	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.
-
-??	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 ?safety 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.
-
-??safety	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 before running `make install'.  (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.
-
-??	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
-?string for details.
-
-??crypt	When linking with the new libc I get unresolved symbols
-	`crypt' and `setkey'.  Why aren't these functions in the
-	libc anymore?
-
-
-{} Removed.  Does not apply anymore.
-
-??	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 to the linker
-    --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.  When linking via gcc, you've got to add
-    -Wl,--dynamic-linker=/lib/ld-linux.so.2
-
-to the gcc command line.
-
-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.
-
-??nonsh	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 )
-
-??excpt	When I run an executable on one system which I compiled on
-	another, I get dynamic linker errors.  Both systems have the same
-	version of glibc installed.  What's wrong?
-
-{ZW} Glibc on one of these systems was compiled with gcc 2.7 or 2.8, the
-other with egcs (any version).  Egcs has functions in its internal
-`libgcc.a' to support exception handling with C++.  They are linked into
-any program or dynamic library compiled with egcs, whether it needs them or
-not.  Dynamic libraries then turn around and export those functions again
-unless special steps are taken to prevent them.
-
-When you link your program, it resolves its references to the exception
-functions to the ones exported accidentally by libc.so.  That works fine as
-long as libc has those functions.  On the other system, libc doesn't have
-those functions because it was compiled by gcc 2.8, and you get undefined
-symbol errors.  The symbols in question are named things like
-`__register_frame_info'.
-
-For glibc 2.0, the workaround is to not compile libc with egcs.  We've also
-incorporated a patch which should prevent the EH functions sneaking into
-libc.  It doesn't matter what compiler you use to compile your program.
-
-For glibc 2.1, we've chosen to do it the other way around: libc.so
-explicitly provides the EH functions.  This is to prevent other shared
-libraries from doing it.
-
-{UD} Starting with glibc 2.1.1 you can compile glibc with gcc 2.8.1 or
-newer since we have explicitly add references to the functions causing the
-problem.  But you nevertheless should use EGCS for other reasons
-(see ?binsize).
-
-{GK} On some Linux distributions for PowerPC, you can see this when you have
-built gcc or egcs from the Web sources (gcc versions 2.95 or earlier), then
-re-built glibc.  This happens because in these versions of gcc, exception
-handling is implemented using an older method; the people making the
-distributions are a little ahead of their time.
-
-A quick solution to this is to find the libgcc.a file that came with the
-distribution (it would have been installed under /usr/lib/gcc-lib), do
-`ar x libgcc.a frame.o' to get the frame.o file out, and add a line saying
-`LDLIBS-c.so += frame.o' to the file `configparms' in the directory you're
-building in.  You can check you've got the right `frame.o' file by running
-`nm frame.o' and checking that it has the symbols defined that you're
-missing.
-
-This will let you build glibc with the C compiler.  The C++ compiler
-will still be binary incompatible with any C++ shared libraries that
-you got with your distribution.
-
-??	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 2.95.3 (or later versions) anyway
-
-??	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@redhat.com>, 1996.
-#
-/^\$ #/ {
-  h
-  s/\$ #\([^ ]*\).*/\1/
-  x
-  s/\$ #[^ ]* *\(.*\)/\$ \1/
-}
-
-/^# / {
-  s/^# \(.*\)/\1/
-  G
-  s/\(.*\)\n\(.*\)/\2 \1/
-}
------------------------------------------------------------------------
-
-??	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.
-
-??	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.suse.de/~kukuk/linux/nisplus.html
-
-??	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-glibc4.diff.gz>
-
-??	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.
-
-
-??	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.
-
-
-??	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
-necessary 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.  See also ?nssdb.
-
-??	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 ?kerhdr).  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.
-
-??	Programs like `logname', `top', `uptime' `users', `w' and
-	`who', show incorrect information about the (number of)
-	users on my system.  Why?
-
-{MK} See ?getlog.
-
-??	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.
-
-??	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.
-
-??	What do I need for C++ development?
-
-{HJ,AJ} You need either egcs 1.1 which comes directly with libstdc++ or
-gcc-2.8.1 together with libstdc++ 2.8.1.1.  egcs 1.1 has the better C++
-support and works directly with glibc 2.1.  If you use gcc-2.8.1 with
-libstdc++ 2.8.1.1, you need to modify libstdc++ a bit.  A patch is available
-as:
-	<ftp://alpha.gnu.org/gnu/libstdc++-2.8.1.1-glibc2.1-diff.gz>
-
-Please note that 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.
-
-{UD} But since in the case of a shared libstdc++ the version numbers should
-be different existing programs will continue to work.
-
-??	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 \
-    -Wl,--start-group -lc -lnss_files -lnss_dns -lresolv -Wl,--end-group
-
-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.
-
-??	I just upgraded my Linux system to glibc and now I get
-	errors whenever I try to link any program.
-
-{ZW} This happens when you have installed glibc as the primary C library but
-have stray symbolic links pointing at your old C library.  If the first
-`libc.so' the linker finds is libc 5, it will use that.  Your program
-expects to be linked with glibc, so the link fails.
-
-The most common case is that glibc put its `libc.so' in /usr/lib, but there
-was a `libc.so' from libc 5 in /lib, which gets searched first.  To fix the
-problem, just delete /lib/libc.so.  You may also need to delete other
-symbolic links in /lib, such as /lib/libm.so if it points to libm.so.5.
-
-{AJ} The perl script test-installation.pl which is run as last step during
-an installation of glibc that is configured with --prefix=/usr should help
-detect these situations.  If the script reports problems, something is
-really screwed up.
-
-??	When I use nscd the machine freezes.
-
-{UD} You cannot use nscd with Linux 2.0.*.  There is functionality missing
-in the kernel and work-arounds are not suitable.  Besides, some parts of the
-kernel are too buggy when it comes to using threads.
-
-If you need nscd, you have to use at least a 2.1 kernel.
-
-Note that I have at this point no information about any other platform.
-
-??	I need lots of open files.  What do I have to do?
-
-{AJ} This is at first a kernel issue.  The kernel defines limits with
-OPEN_MAX the number of simultaneous open files and with FD_SETSIZE the
-number of used file descriptors.  You need to change these values in your
-kernel and recompile the kernel so that the kernel allows more open
-files.  You don't necessarily need to recompile the GNU C library since the
-only place where OPEN_MAX and FD_SETSIZE is really needed in the library
-itself is the size of fd_set which is used by select.
-
-The GNU C library is now select free.  This means it internally has no
-limits imposed by the `fd_set' type.  Instead all places where the
-functionality is needed the `poll' function is used.
-
-If you increase the number of file descriptors in the kernel you don't need
-to recompile the C library.
-
-{UD} You can always get the maximum number of file descriptors a process is
-allowed to have open at any time using
-
-	number = sysconf (_SC_OPEN_MAX);
-
-This will work even if the kernel limits change.
-
-??	How do I get the same behavior on parsing /etc/passwd and
-	/etc/group as I have with libc5 ?
-
-{TK} The name switch setup in /etc/nsswitch.conf selected by most Linux
-distributions does not support +/- and netgroup entries in the files like
-/etc/passwd.  Though this is the preferred setup some people might have
-setups coming over from the libc5 days where it was the default to recognize
-lines like this.  To get back to the old behaviour one simply has to change
-the rules for passwd, group, and shadow in the nsswitch.conf file as
-follows:
-
-passwd: compat
-group:  compat
-shadow: compat
-
-passwd_compat: nis
-group_compat: nis
-shadow_compat: nis
-
-??libs	What needs to be recompiled when upgrading from glibc 2.0 to glibc
-	2.1?
-
-{AJ,CG} If you just upgrade the glibc from 2.0.x (x <= 7) to 2.1, binaries
-that have been linked against glibc 2.0 will continue to work.
-
-If you compile your own binaries against glibc 2.1, you also need to
-recompile some other libraries.  The problem is that libio had to be changed
-and therefore libraries that are based or depend on the libio of glibc,
-e.g. ncurses, slang and most C++ libraries, need to be recompiled.  If you
-experience strange segmentation faults in your programs linked against glibc
-2.1, you might need to recompile your libraries.
-
-Another problem is that older binaries that were linked statically against
-glibc 2.0 will reference the older nss modules (libnss_files.so.1 instead of
-libnss_files.so.2), so don't remove them.  Also, the old glibc-2.0 compiled
-static libraries (libfoo.a) which happen to depend on the older libio
-behavior will be broken by the glibc 2.1 upgrade.  We plan to produce a
-compatibility library that people will be able to link in if they want
-to compile a static library generated against glibc 2.0 into a program
-on a glibc 2.1 system.  You just add -lcompat and you should be fine.
-
-The glibc-compat add-on will provide the libcompat.a library, the older
-nss modules, and a few other files.  Together, they should make it
-possible to do development with old static libraries on a glibc 2.1
-system.  This add-on is still in development.  You can get it from
-	<ftp://alpha.gnu.org/gnu/glibc/glibc-compat-2.1.tar.gz>
-but please keep in mind that it is experimental.
-
-??	Why is extracting files via tar so slow?
-
-{AJ} Extracting of tar archives might be quite slow since tar has to look up
-userid and groupids and doesn't cache negative results.  If you have nis or
-nisplus in your /etc/nsswitch.conf for the passwd and/or group database,
-each file extractions needs a network connection.  There are two possible
-solutions:
-
-- do you really need NIS/NIS+ (some Linux distributions add by default
-  nis/nisplus even if it's not needed)?  If not, just remove the entries.
-
-- if you need NIS/NIS+, use the Name Service Cache Daemon nscd that comes
-  with glibc 2.1.
-
-??	Compiling programs I get parse errors in libio.h (e.g. "parse error
-	before `_IO_seekoff'").  How should I fix this?
-
-{AJ} You might get the following errors when upgrading to glibc 2.1:
-
-  In file included from /usr/include/stdio.h:57,
-		   from ...
-  /usr/include/libio.h:335: parse error before `_IO_seekoff'
-  /usr/include/libio.h:335: parse error before `_G_off64_t'
-  /usr/include/libio.h:336: parse error before `_IO_seekpos'
-  /usr/include/libio.h:336: parse error before `_G_fpos64_t'
-
-The problem is a wrong _G_config.h file in your include path.  The
-_G_config.h file that comes with glibc 2.1 should be used and not one from
-libc5 or from a compiler directory.  To check which _G_config.h file the
-compiler uses, compile your program with `gcc -E ...|grep G_config.h' and
-remove that file.  Your compiler should pick up the file that has been
-installed by glibc 2.1 in your include directory.
-
-??	After upgrading to glibc 2.1, libraries that were compiled against
-	glibc 2.0.x don't work anymore.
-
-{AJ} See ?libs.
-
-??nssdb	What happened to the Berkeley DB libraries?  Can I still use db
-	in /etc/nsswitch.conf?
-
-{AJ} Due to too many incompatible changes in disk layout and API of Berkeley
-DB and a too tight coupling of libc and libdb, the db library has been
-removed completely from glibc 2.2.  The only place that really used the
-Berkeley DB was the NSS db module.
-
-The NSS db module has been rewritten to support a number of different
-versions of Berkeley DB for the NSS db module.  Currently the releases 2.x
-and 3.x of Berkeley DB are supported.  The older db 1.85 library is not
-supported.  You can use the version from glibc 2.1.x or download a version
-from Sleepycat Software (http://www.sleepycat.com).  The library has to be
-compiled as shared library and installed in the system lib directory
-(normally /lib).  The library needs to have a special soname to be found by
-the NSS module.
-
-If public structures change in a new Berkeley db release, this needs to be
-reflected in glibc.
-
-Currently the code searches for libraries with a soname of "libdb.so.3"
-(that's the name from db 2.4.14 which comes with glibc 2.1.x) and
-"libdb-3.0.so" (the name used by db 3.0.55 as default).
-
-The nss_db module is now in a separate package since it requires a database
-library being available.
-
-??	What has do be done when upgrading to glibc 2.2?
-
-{AJ} The upgrade to glibc 2.2 should run smoothly, there's in general no
-need to recompile programs or libraries.  Nevertheless, some changes might
-be needed after upgrading:
-- The utmp daemon has been removed and is not supported by glibc anymore.
-  If it has been in use, it should be switched off.
-- Programs using IPv6 have to be recompiled due to incompatible changes in
-  sockaddr_in6 by the IPv6 working group.
-- The Berkeley db libraries have been removed (for details see ?nssdb).
-- The format of the locale files has changed, all locales should be
-  regenerated with localedef.  All statically linked applications which use
-  i18n should be recompiled, otherwise they'll not be localized.
-- glibc comes with a number of new applications.  For example ldconfig has
-  been implemented for glibc, the libc5 version of ldconfig is not needed
-  anymore.
-- There's no more K&R compatibility in the glibc headers.  The GNU C library
-  requires a C compiler that handles especially prototypes correctly.
-  Especially gcc -traditional will not work with glibc headers.
-
-Please read also the NEWS file which is the authoritative source for this
-and gives more details for some topics.
-
-??	The makefiles want to do a CVS commit.
-
-{} Removed.  Does not apply anymore.
-
-??	When compiling C++ programs, I get a compilation error in streambuf.h.
-
-{BH} You are using g++ 2.95.2? After upgrading to glibc 2.2, you need to
-apply a patch to the include files in /usr/include/g++, because the fpos_t
-type has changed in glibc 2.2.  The patch is at
-
-  http://www.haible.de/bruno/gccinclude-glibc-2.2-compat.diff
-
-??	When recompiling GCC, I get compilation errors in libio.
-
-{BH} You are trying to recompile gcc 2.95.2?  Use gcc 2.95.3 instead.
-This version is needed because the fpos_t type and a few libio internals
-have changed in glibc 2.2, and gcc 2.95.3 contains a corresponding patch.
-
-??	Why shall glibc never get installed on GNU/Linux systems in
-/usr/local?
-
-{AJ} The GNU C compiler treats /usr/local/include and /usr/local/lib in a
-special way, these directories will be searched before the system
-directories.  Since on GNU/Linux the system directories /usr/include and
-/usr/lib contain a --- possibly different --- version of glibc and mixing
-certain files from different glibc installations is not supported and will
-break, you risk breaking your complete system.  If you want to test a glibc
-installation, use another directory as argument to --prefix.  If you like to
-install this glibc version as default version, overriding the existing one,
-use --prefix=/usr and everything will go in the right places.
-
-??	When recompiling GCC, I get compilation errors in libstdc++.
-
-{BH} You are trying to recompile gcc 3.2?  You need to patch gcc 3.2,
-because some last minute changes were made in glibc 2.3 which were not
-known when gcc 3.2 was released.  The patch is at
-
-  http://www.haible.de/bruno/gcc-3.2-glibc-2.3-compat.diff
-
-? Source and binary incompatibilities, and what to do about them
-
-??	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 ?signal for details.
-
-??getlog	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.
-
-??	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.  For former is very much preferred
-(see ?tzdb).
-
-??	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.
-
-??kerhdr	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.
-
-??	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.
-
-??signal	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().
-
-
-??string	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.  This might lead to problems with
-existing codes but it is explicitly allowed by ISO C.
-
-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.
-
-?? 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.
-
-To fix those programs you've got to initialize the variable at run time.
-This can be done, e.g. in main, like:
-
-   static FILE *InPtr;
-   int main(void)
-   {
-     InPtr = stdin;
-   }
-
-or by constructors (beware this is gcc specific):
-
-   static FILE *InPtr;
-   static void inPtr_construct (void) __attribute__((constructor));
-   static void inPtr_construct (void) { InPtr = stdin; }
-
-
-??	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).
-
-??	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.
-
-??	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.
-
-??	When using the db-2 library which comes with glibc is used in
-	the Perl db modules the testsuite is not passed.  This did not
-	happen with db-1, gdbm, or ndbm.
-
-{} Removed.  Does not apply anymore.
-
-??	The pow() inline function I get when including <math.h> is broken.
-	I get segmentation faults when I run the program.
-
-{UD} Nope, the implementation is correct.  The problem is with egcs version
-prior to 1.1.  I.e., egcs 1.0 to 1.0.3 are all broken (at least on Intel).
-If you have to use this compiler you must define __NO_MATH_INLINES before
-including <math.h> to prevent the inline functions from being used.  egcs 1.1
-fixes the problem.  I don't know about gcc 2.8 and 2.8.1.
-
-??	The sys/sem.h file lacks the definition of `union semun'.
-
-{UD} Nope.  This union has to be provided by the user program.  Former glibc
-versions defined this but it was an error since it does not make much sense
-when thinking about it.  The standards describing the System V IPC functions
-define it this way and therefore programs must be adopted.
-
-??	Why has <netinet/ip_fw.h> disappeared?
-
-{AJ} The corresponding Linux kernel data structures and constants are
-totally different in Linux 2.0 and Linux 2.2.  This situation has to be
-taken care in user programs using the firewall structures and therefore
-those programs (ipfw is AFAIK the only one) should deal with this problem
-themselves.
-
-??	I get floods of warnings when I use -Wconversion and include
-	<string.h> or <math.h>.
-
-{ZW} <string.h> and <math.h> intentionally use prototypes to override
-argument promotion.  -Wconversion warns about all these.  You can safely
-ignore the warnings.
-
--Wconversion isn't really intended for production use, only for shakedown
-compiles after converting an old program to standard C.
-
-
-??	After upgrading to glibc 2.1, I receive errors about
-	unresolved symbols, like `_dl_initial_searchlist' and can not
-	execute any binaries.  What went wrong?
-
-{AJ} This normally happens if your libc and ld (dynamic linker) are from
-different releases of glibc.  For example, the dynamic linker
-/lib/ld-linux.so.2 comes from glibc 2.0.x, but the version of libc.so.6 is
-from glibc 2.1.
-
-The path /lib/ld-linux.so.2 is hardcoded in every glibc2 binary but
-libc.so.6 is searched via /etc/ld.so.cache and in some special directories
-like /lib and /usr/lib.  If you run configure with another prefix than /usr
-and put this prefix before /lib in /etc/ld.so.conf, your system will break.
-
-So what can you do?  Either of the following should work:
-
-* Run `configure' with the same prefix argument you've used for glibc 2.0.x
-  so that the same paths are used.
-* Replace /lib/ld-linux.so.2 with a link to the dynamic linker from glibc
-  2.1.
-
-You can even call the dynamic linker by hand if everything fails.  You've
-got to set LD_LIBRARY_PATH so that the corresponding libc is found and also
-need to provide an absolute path to your binary:
-
-	LD_LIBRARY_PATH=<path-where-libc.so.6-lives> \
-	<path-where-corresponding-dynamic-linker-lives>/ld-linux.so.2 \
-	<path-to-binary>/binary
-
-For example `LD_LIBRARY_PATH=/libold /libold/ld-linux.so.2 /bin/mv ...'
-might be useful in fixing a broken system (if /libold contains dynamic
-linker and corresponding libc).
-
-With that command line no path is used.  To further debug problems with the
-dynamic linker, use the LD_DEBUG environment variable, e.g.
-`LD_DEBUG=help echo' for the help text.
-
-If you just want to test this release, don't put the lib directory in
-/etc/ld.so.conf.  You can call programs directly with full paths (as above).
-When compiling new programs against glibc 2.1, you've got to specify the
-correct paths to the compiler (option -I with gcc) and linker (options
---dynamic-linker, -L and --rpath).
-
-??	bonnie reports that char i/o with glibc 2 is much slower than with
-	libc5.  What can be done?
-
-{AJ} The GNU C library uses thread safe functions by default and libc5 used
-non thread safe versions.  The non thread safe functions have in glibc the
-suffix `_unlocked', for details check <stdio.h>.  Using `putc_unlocked' etc.
-instead of `putc' should give nearly the same speed with bonnie (bonnie is a
-benchmark program for measuring disk access).
-
-??	Programs compiled with glibc 2.1 can't read db files made with glibc
-	2.0.  What has changed that programs like rpm break?
-
-{} Removed.  Does not apply anymore.
-
-??	Autoconf's AC_CHECK_FUNC macro reports that a function exists, but
-	when I try to use it, it always returns -1 and sets errno to ENOSYS.
-
-{ZW} You are using a 2.0 Linux kernel, and the function you are trying to
-use is only implemented in 2.1/2.2.  Libc considers this to be a function
-which exists, because if you upgrade to a 2.2 kernel, it will work.  One
-such function is sigaltstack.
-
-Your program should check at runtime whether the function works, and
-implement a fallback.  Note that Autoconf cannot detect unimplemented
-functions in other systems' C libraries, so you need to do this anyway.
-
-??	My program segfaults when I call fclose() on the FILE* returned
-	from setmntent().  Is this a glibc bug?
-
-{GK} No.  Don't do this.  Use endmntent(), that's what it's for.
-
-In general, you should use the correct deallocation routine.  For instance,
-if you open a file using fopen(), you should deallocate the FILE * using
-fclose(), not free(), even though the FILE * is also a pointer.
-
-In the case of setmntent(), it may appear to work in most cases, but it
-won't always work.  Unfortunately, for compatibility reasons, we can't
-change the return type of setmntent() to something other than FILE *.
-
-??	I get "undefined reference to `atexit'"
-
-{UD} This means that your installation is somehow broken.  The situation is
-the same as for 'stat', 'fstat', etc (see ?nonsh).  Investigate why the
-linker does not pick up libc_nonshared.a.
-
-If a similar message is issued at runtime this means that the application or
-DSO is not linked against libc.  This can cause problems since 'atexit' is
-not exported anymore.
-
-
-? Miscellaneous
-
-??	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.
-
-??	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.
-
-{PB} The 2.1 release of GNU libc aims to comply with the current versions of
-all the relevant standards.  The IPv6 support libraries for older Linux
-systems used a different naming convention and so code written to work with
-them may need to be modified.  If the standards make incompatible changes in
-the future then the libc may need to change again.
-
-IPv6 will not work with a 2.0.x kernel.  When kernel 2.2 is released it
-should contain all the necessary support; until then you should use the
-latest 2.1.x release you can find.  As of 98/11/26 the currently recommended
-kernel for IPv6 is 2.1.129.
-
-Also, as of the 2.1 release the IPv6 API provided by GNU libc is not
-100% complete.
-
-??tzdb	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, if you insist on using TZ instead of the timezone
-database (see below), 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 /etc/localtime pointing to /usr/share/zoneinfo/NAME (NAME
-is the returned value from tzselect).  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.
-
-??	What other sources of documentation about glibc are available?
-
-{AJ} The FSF has a page about the GNU C library at
-<http://www.gnu.org/software/libc/>.  The problem data base of open and
-solved bugs in GNU libc is available at
-<http://www-gnats.gnu.org:8080/cgi-bin/wwwgnats.pl>.  Eric Green has written
-a HowTo for converting from Linux libc5 to glibc2.  The HowTo is accessible
-via the FSF page and at <http://www.imaxx.net/~thrytis/glibc>.  Frodo
-Looijaard describes a different way installing glibc2 as secondary libc at
-<http://huizen.dds.nl/~frodol/glibc>.
-
-Please note that this is not a complete list.
-
-??	The timezone string for Sydney/Australia is wrong since even when
-	daylight saving time is in effect the timezone string is EST.
-
-{UD} The problem for some timezones is that the local authorities decided
-to use the term "summer time" instead of "daylight saving time".  In this
-case the abbreviation character `S' is the same as the standard one.  So,
-for Sydney we have
-
-	Eastern Standard Time	= EST
-	Eastern Summer Time	= EST
-
-Great!  To get this bug fixed convince the authorities to change the laws
-and regulations of the country this effects.  glibc behaves correctly.
-
-??make	I've build make 3.77 against glibc 2.1 and now make gets
-	segmentation faults.
-
-{} Removed.  Does not apply anymore, use make 3.79 or newer.
-
-??	Why do so many programs using math functions fail on my AlphaStation?
-
-{AO} The functions floor() and floorf() use an instruction that is not
-implemented in some old PALcodes of AlphaStations.  This may cause
-`Illegal Instruction' core dumps or endless loops in programs that
-catch these signals.  Updating the firmware to a 1999 release has
-fixed the problem on an AlphaStation 200 4/166.
-
-??	The conversion table for character set XX does not match with
-what I expect.
-
-{UD} I don't doubt for a minute that some of the conversion tables contain
-errors.  We tried the best we can and relied on automatic generation of the
-data to prevent human-introduced errors but this still is no guarantee.  If
-you think you found a problem please send a bug report describing it and
-give an authoritive reference.  The latter is important since otherwise
-the current behaviour is as good as the proposed one.
-
-Before doing this look through the list of known problem first:
-
-- the GBK (simplified Chinese) encoding is based on Unicode tables.  This
-  is good.  These tables, however, differ slightly from the tables used
-  by the M$ people.  The differences are these [+ Unicode, - M$]:
-
-    +0xA1AA 0x2015
-    +0xA844 0x2014
-    -0xA1AA 0x2014
-    -0xA844 0x2015
-
-  In addition the Unicode tables contain mappings for the GBK characters
-  0xA8BC, 0xA8BF, 0xA989 to 0xA995, and 0xFE50 to 0xFEA0.
-
-- when mapping from EUC-CN to GBK and vice versa we ignore the fact that
-  the coded character at position 0xA1A4 maps to different Unicode
-  characters.  Since the iconv() implementation can do whatever it wants
-  if it cannot directly map a character this is a perfectly good solution
-  since the semantics and appearance of the character does not change.
-
-??	How can I find out which version of glibc I am using in the moment?
-
-{UD} If you want to find out about the version from the command line simply
-run the libc binary.  This is probably not possible on all platforms but
-where it is simply locate the libc DSO and start it as an application.  On
-Linux like
-
-	/lib/libc.so.6
-
-This will produce all the information you need.
-
-What always will work is to use the API glibc provides.  Compile and run the
-following little program to get the version information:
-
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-#include <stdio.h>
-#include <gnu/libc-version.h>
-int main (void) { puts (gnu_get_libc_version ()); return 0; }
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-This interface can also obviously be used to perform tests at runtime if
-this should be necessary.
-
-??	Context switching with setcontext() does not work from within
-	signal handlers.
-
-{DMT} The Linux implementations (IA-64, S390 so far) of setcontext()
-supports synchronous context switches only.  There are several reasons for
-this:
-
-- UNIX provides no other (portable) way of effecting a synchronous
-  context switch (also known as co-routine switch).  Some versions
-  support this via setjmp()/longjmp() but this does not work
-  universally.
-
-- As defined by the UNIX '98 standard, the only way setcontext()
-  could trigger an asychronous context switch is if this function
-  were invoked on the ucontext_t pointer passed as the third argument
-  to a signal handler.  But according to draft 5, XPG6, XBD 2.4.3,
-  setcontext() is not among the set of routines that may be called
-  from a signal handler.
-
-- If setcontext() were to be used for asynchronous context switches,
-  all kinds of synchronization and re-entrancy issues could arise and
-  these problems have already been solved by real multi-threading
-  libraries (e.g., POSIX threads or Linux threads).
-
-- Synchronous context switching can be implemented entirely in
-  user-level and less state needs to be saved/restored than for an
-  asynchronous context switch.  It is therefore useful to distinguish
-  between the two types of context switches.  Indeed, some
-  application vendors are known to use setcontext() to implement
-  co-routines on top of normal (heavier-weight) pre-emptable threads.
-
-It should be noted that if someone was dead-bent on using setcontext()
-on the third arg of a signal handler, then IA-64 Linux could support
-this via a special version of sigaction() which arranges that all
-signal handlers start executing in a shim function which takes care of
-saving the preserved registers before calling the real signal handler
-and restoring them afterwards.  In other words, we could provide a
-compatibility layer which would support setcontext() for asynchronous
-context switches.  However, given the arguments above, I don't think
-that makes sense.  setcontext() provides a decent co-routine interface
-and we should just discourage any asynchronous use (which just calls
-for trouble at any rate).
-
-
-
-Answers were given by:
-{UD} Ulrich Drepper, <drepper@redhat.com>
-{DMT} David Mosberger-Tang, <davidm@hpl.hp.com>
-{RM} Roland McGrath, <roland@gnu.org>
-{AJ} Andreas Jaeger, <aj@suse.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@suse.de>
-{GK} Geoffrey Keating, <geoffk@redhat.com>
-{HJ} H.J. Lu, <hjl@gnu.org>
-{CG} Cristian Gafton, <gafton@redhat.com>
-{AO} Alexandre Oliva, <aoliva@redhat.com>
-{BH} Bruno Haible, <haible@clisp.cons.org>
-{SM} Steven Munroe, <sjmunroe@us.ibm.com>
-{CO} Carlos O'Donell, <carlos@systemhalted.org>
-
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