[FFmpeg-devel] [PATCH] Add log2 check to configure and equivalent to internal.h

[Reimar Döffinger]

On Sat, Jul 11, 2009 at 12:18:03AM +0100, M?ns Rullg?rd wrote:
> Alex Converse <alex.converse at gmail.com> writes:
> 
> > Hi,
> >
> > If someone on a system without log2 could test this, that would be great.
> >
> > Regards,
> > Alex Converse
> >
> > diff --git a/configure b/configure
> > index 7998273..48630f1 100755
> > --- a/configure
> > +++ b/configure
> > @@ -911,6 +911,7 @@ HAVE_LIST="
> >      libdc1394_1
> >      libdc1394_2
> >      llrint
> > +    log2
> >      loongson
> >      lrint
> >      lrintf
> > @@ -2078,7 +2079,7 @@ check_lib math.h sin -lm
> >  check_lib va/va.h vaInitialize -lva
> >  
> >  # test for C99 functions in math.h
> > -for func in llrint lrint lrintf round roundf truncf; do
> > +for func in log2 llrint lrint lrintf round roundf truncf; do
> >      check_exec <<EOF && enable $func || disable $func
> >  #include <math.h>
> >  int main(void) { return ($func(3.999f) > 0)?0:1; }
> 
> What's with that weird runtime check anyway?  Looks pretty useless to
> me.

Not sure if I understand you right, but if the compiler optimizes away
the function call it wouldn't be a good way to check if the function is
available...