Hello. Though the GNU libc manual says: "Mathematically, the tangent function has singularities at odd multiples of pi/2. If the argument x is too close to one of these singularities, tan will signal overflow." the next code: _________________________ #include <stdio.h> #include <math.h> #include <fenv.h> int main (void) { double val1; int raised; #if defined(FE_OVERFLOW) feclearexcept (FE_ALL_EXCEPT); val1 = tan (M_PI/2); raised = fetestexcept (FE_OVERFLOW); if (raised) printf ("Overflow\n"); else printf ("No overflow\n"); printf ("%G\n",val1); #else printf ("FE_OVERFLOW not defined\n"); printf ("%G\n",tan(M_PI/2)); #endif return 0; } _________________________ compiled this way: gcc -Wall -lm -g -o test-float.out test-float.c is giving this output: ./test-float.out No overflow 1.63312E+16 Even compiling this way: gcc -ftrapv -fwrapv -fexceptions -Wall -lm -g -o test-float.out\ test-float.c the output is the same. So, anyone knows how can I get tan(pi/2) to raise the overflow exception. Thanks.