[Pixman] [PATCH] Fix pixman build with older GCC releases

[Brad Smith]

On Thu, Oct 10, 2013 at 02:16:29AM +0300, Siarhei Siamashka wrote:
> Have you verified that this actually works as expected with GCC 3.3?

I had not as the systems using 3.3 are hard to come by, but I was able
to resurrect the port we had quite awhile ago for a 3.3 package and see
that the macro did not work as I expected.

> For example, when compiling pixman with TCC (it does not support
> __builtin_clz), this configure check thinks that __builtin_clz is
> supported, but then the build fails at the linking stage with
> "undefined symbol '__builtin_clz'" error.
> 
> The other similar checks from configure.ac are all using AC_LINK_IFELSE
> instead of AC_COMPILE_IFELSE.

I see this macro does what I would expect and fixes the test.

> > +unsigned int x = 11; int main (void) { __builtin_clz(x); }
> 
> "return __builtin_clz (x)" would be a cleaner warning-free code.

Ok, I will post an updated patch.

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