"Maciej W. Rozycki" <macro@ds2.pg.gda.pl> writes:
> On 1 Jun 2001, Andreas Jaeger wrote:
>
>> #include "sys/tas.h"
>> +
>> +#ifdef __NR__test_and_set
>> +# ifdef __ASSUME__TEST_AND_SET
>> +# define __have_no__test_and_set 0
>>
>> Don't add this, compare how we do it in similar cases.
>
> Hmm, I looked at sysdeps/unix/sysv/linux/getcwd.c. It does it in a
> similar way. What's wrong with this approach? I'm just asking -- it
> looks I do not always guess glibc rules right and not everything is
> documented.
We normally do not define anything to 0 - unless there's no other
way. And looking briefly over your code there should be other
solutions. Sorry, I'm limited in time currently, otherwise I would
rewrite it myself.
Look at i386/lockf64.c for a cleaner example.
> Actually I tried to avoid macros if at all possible but gcc refuses to
> eliminate code even if that's something like:
>
> static const int var = 1;
> <...>
> if (var)
> <...>
>
> It still generates the code to check the value of var, sigh...
>
> Also I feel a bit uneasy about placing the "#ifdef
> __ASSUME__TEST_AND_SET" condition outside -- __NR__test_and_set might be
> undefined due to outdated kernel headers even if someone specified the
> --enable-kernel option. Is it considered justified within glibc to bail
> out at the compilation time in this case?
We check that for the kernel headers in configure.
>> extern int _test_and_set (int *p, int v) __THROW;
>> +extern int ___test_and_set (int *p, int v) __THROW;
>>
>> Why do you export this here?
>
> It's a syscall wrapper. We want to export syscall wrappers, don't
> we?
No, not everything - we already export _test_and_set and that should
be enough.
> And if we export a symbol, we should also declare it -- programs declaring
> library symbols themselves are broken and doomed to fail sooner or later
> -- have you seen what happens on glibc systems to old programs which
> declare <string.h> functions due to the lack of appropriate declarations
> in system headers at one time?
>
> If we don't want to export the wrapper, then fine -- I'll remove both the
> symbol and the declaration.
Andreas
--
Andreas Jaeger
SuSE Labs aj@suse.de
private aj@arthur.inka.de
http://www.suse.de/~aj
