Stricter check for math.h functions

GCC is sometimes able to optimise constant calls to these functions,
incorrectly indicating that they exist.  Unoptimised calls will then
fail to link.

Originally committed as revision 21749 to svn://svn.ffmpeg.org/ffmpeg/trunk

diff --git a/configure b/configure
index f324e17..b28b468 100755 (executable)
--- a/configure
+++ b/configure
@@ -675,7 +675,8 @@ check_mathfunc(){
     disable $func
     check_ld "$@" <<EOF && enable $func
 #include <math.h>
-int main(void){ $func(0); return 0; }
+float foo(float f) { return $func(f); }
+int main(void){ return 0; }
 EOF
 }