Akim Demaille <[EMAIL PROTECTED]> writes:
> It's a pity that the Autoconf documentation gives hint about broken
> functions only for functions that have their own AC_FUNC_FOO, likewise
> for headers. If you know a function which should be AC_CHECK_FUNC'd or
> AC_REPLACE_FUNC'd, please, submit so short words which describe where
> they are missing, what kind of bug you can meet, and the best strategy
> to work around these.
Here are the things that I've run into for INN:
* Calls to inet_ntoa are miscomplied by gcc on IRIX systems due to a
difference of opinion over the ABI for passing small structs on the
stack. I generally just test to see if inet_ntoa works and use my own
replacement if it doesn't. Test available if anyone wants it.
* Many systems have an snprintf that isn't C99-compliant, including glibc
2.0, Solaris prior to (I think) version 8 (maybe 7), and other systems.
They return -1 rather than the total number of bytes needed for the
output if the output was truncated, mishandle snprintf(NULL, 0, ...),
or both. Test available if anyone wants it. I replace the standard
version one based on [EMAIL PROTECTED]'s (also used in Mutt) with some
modifications to make it C99-compliant.
* BSDI has 64-bit off_t but is missing fseeko and ftello. They're
possible to implement using fsetpos and fgetpos because fpos_t happens
to be a typedef for off_t provided you're not using strict ANSI mode.
Test and functions available.
* SysV systems (e.g. Solaris) often don't have hstrerror.
* BSD systems (e.g. BSDI) often don't have pread and pwrite, which can be
faked provided you don't need atomicity across multiple threads.
* SysV systems (e.g. Solaris) often don't have setenv, which can be
implemented in terms of putenv.
* AIX 4.1 doesn't have seteuid, but you can fake it using setreuid under
some situations.
* Ultrix didn't have strtok, IIRC. I no longer have any Ultrix machines.
* SunOS didn't have strerror, IIRC. I no longer have any SunOS
machines.
* Really, really old BSD systems don't have the mem* functions. Probably
not worrying about except in *extremely* portable code any more. I'm
sure pretty much everyone here has seen the standard memcpy in terms of
bcopy macros and the like, so I won't bother to repeat them.
* Some really old systems may not have getopt; I'm not sure which ones
fall into that category.
* You can fake atexit on SunOS passably well, or so I've been told (not
tested it myself) with:
#ifndef HAVE_ATEXIT
# define atexit(arg) on_exit((arg), 0)
#endif
* You can fake strtoul passably well with:
#ifndef HAVE_STRTOUL
# define strtoul(a, b, c) strtol((a), (b), (c))
#endif
* I'm currently using:
#include <sys/types.h>
#ifdef HAVE_STDINT_H
# include <stdint.h>
#endif
#ifdef HAVE_SYS_BITYPES_H
# include <sys/bitypes.h>
#endif
to try to find int32_t, uint32_t, and friends. You still need to check
for them since a lot of systems simply don't have them at all (IRIX,
HP-UX, I think). I do a bit of preliminary checking of the sizes of
likely things to find a 4-byte data type and then define int32_t to
that if needed; macros available if anyone wants them. For SCO, you
need to pick them up from sys/bitypes.h instead of creating your own
because otherwise you'll conflict with the ones in sys/bitypes.h at the
most annoying times.
* getpagesize has a whole massive boatload of stuff that you can do to
find the page size if it isn't found; the standard mmap test has a lot
of it.
* There are about six different ways to find the maximum number of open
file descriptors, but thankfully pretty much everyone has getrlimit
these days. (If you don't, fall back on sysconf, then getdtabsize,
then ulimit, then the #define in sys/param.h, then the POSIX
guarantee.) Use getrlimit in preference to sysconf; on Linux, sysconf
can return the wrong value.
* You can fake mkfifo with mknod; not sure if enough platforms still
don't have mkfifo to care much.
* Signal handling, figuring out if you have sigaction or have to use
signal, trying to not have to reset your signal handlers in the signal
handler, etc. is another large blob of stuff that I think most people
here have seen.
* statvfs vs. statfs and all its header files to find file system usage.
GNU du has all this stuff; so does INN's inndf.
* On really old systems, you may have to use wait3 instead of waitpid.
* Some systems don't have gethostname and you have to use uname instead,
or several other odd techniques.
* Figuring out how to set a socket nonblocking involves various issues;
in general, you want to avoid using O_NDELAY even if it's available and
fall back on ioctl with FNDELAY if O_NONBLOCK isn't available.
* File locking (fcntl vs. flock vs. lockf) is a whole different set of
issues.
> Patches are definitely the most appreciated means to contribute,
I would, but the quarter is starting next week and I'm *horribly* busy.
Sorry. :/
> nevertheless, plain text is accepted, we will integrate it into the
> documentation ourselves.
Thanks!
The above-referenced tests will make it into the autoconf macro archive as
soon as 2.50 is released so that I can break them out into separate files
without using automake; I don't have the time right now to do the work
twice or I would have submitted them already. :/
--
Russ Allbery ([EMAIL PROTECTED]) <http://www.eyrie.org/~eagle/>
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