[FFmpeg-cvslog] r12620 - trunk/configure

[İsmail Dönmez]

On Sat, Mar 29, 2008 at 10:09 PM, ?smail D?nmez <ismail at namtrac.org> wrote:
> On Sat, Mar 29, 2008 at 10:02 PM, matthieu castet
>
>
> <castet.matthieu at free.fr> wrote:
>  >
>  > ?smail D?nmez wrote:
>  >  > On Fri, Mar 28, 2008 at 10:04 PM, matthieu castet
>  >  > <castet.matthieu at free.fr> wrote:
>  >  >> diego wrote:
>  >  >>  > Author: diego
>  >  >>  > Date: Fri Mar 28 12:53:37 2008
>  >  >>  > New Revision: 12620
>  >  >>  >
>  >  >>  > Log:
>  >  >>  > Replace hackish CFLAGS 64 bit test by a proper compilation check.
>  >  >>  > patch by ?smail D?nmez, ismail namtrac org
>  >  >>  >
>  >  >>  >
>  >  >>  > Modified:
>  >  >>  >    trunk/configure
>  >  >>  >
>  >  >>  > Modified: trunk/configure
>  >  >>  > ==============================================================================
>  >  >>
>  >  >>> +        check_cc <<EOF && enable fast_64bit && arch="x86_64"
>  >  >>  > +        int test[sizeof(char*) - 7];
>  >  >>  > +EOF
>  >  >>  Just for info gcc see "sizeof(char*) - 7" as a big integer not a
>  >  >>  negative integer.
>  >  >>
>  >  >>  The check still failed on 32 bits because of array overflow. I wonder if
>  >  >>  it was the expected behaviour.
>  >  >
>  >  > Yes thats the point, it won't compile on 32bit. Thats why we use check_cc.
>  >  my point was is there something in C standard that prevent to allocate
>  >  such big array ?
>  >
>  >  Yes gcc failed because of array overflow, but not all C compiler are gcc.
>  >
>  >  May be it could be more safe to make "sizeof(char*) - 7" signed and be
>  >  in the case of negative array (which is in the C standard).
>
>  sizeof(char*) is 4 on 32bit so you are trying to do int test[-3] which
>  should fail on all valid compilers.

Ah so gcc wraps that to an unsigned number, I see. Would
(signed)(sizeof(char*) - 7) work for everyone?

Regards,
ismail

-- 
Never learn by your mistakes, if you do you may never dare to try again.