> Oops, the configure script compiling with -O2 optimization. Clearly not the best option for this kind of tests.
> The compilation of the following code still suceesss. > > #include <math.h> > > int a; > > int > main () > { > float f = 0.0; > a = isinf (f); > return 0; > } The compiler knows the answer of isinf (0) so it again optimizes away the call. Try something like: int a; int main (int argc, char *argv[]) { a = isinf ((double) argc); return 0; } or additionally compile with -fno-builtin. -- Eric Botcazou