[C] NaN

cat 1.c 
#include <stdio.h>
#include <signal.h>
#include <math.h>

void h(int s){
	printf("SIG: %d\n", s);
}

int main(int argc, char **arg){
	signal(SIGFPE, h);
	float a = log(-1.);
	printf("a = %g\n", a);
}

gcc 1.c -lm && ./a.out 
a = nan

if (isnan(f)) {
    raise(SIGFPE);
}

#include <stdio.h>
#include <signal.h>
#include <stdlib.h>
#include <math.h>
#include <limits.h>

void h(int s){
	printf("SIG: %d\n", s);
	exit(-1);
}

int main(int argc, char **arg){
	signal(SIGFPE, h);
	float a = log(-1.);
	double x = exp(100.);
	printf("a = %g, x = %g\n", a, x);
	float xx = (float)x;
	printf("xx = %g\n", xx);
	int A = INT_MIN;
	int B = A/0;
	printf("B = %d\n", B);
}

gcc 1.c -lm && ./a.out 
1.c: В функции <<main>>:
1.c:20:11: предупреждение: деление на ноль [-Wdiv-by-zero]
a = nan, x = 2.68812e+43
xx = inf
SIG: 8

	int A = INT_MIN;
	int B = A/0;
	printf("B = %d\n", B);

gcc 1.c && ./a.out 
1.c: В функции <<main>>:
1.c:14:11: предупреждение: деление на ноль [-Wdiv-by-zero]
Исключение в операции с плавающей точкой

#ifdef WIN32
#include <windows.h>
extern "C" void set_fpe_except()
{
  int cw = _controlfp (0, 0);
  cw &= ~ (EM_OVERFLOW | EM_UNDERFLOW | EM_ZERODIVIDE | EM_DENORMAL | EM_INVALID);
  _controlfp (cw, MCW_EM);
}
#else
extern "C" void set_fpe_except()
{
  //http://www.website.masmforum.com/tutorials/fptute/fpuchap1.htm
  unsigned m = 0;
  asm ("fstcw %0" : : "m" (*&m) );
  asm ("fwait");
  m ^= 0x1f; //turn on all exceptions!
  m |= (1 << 8);
  m |= (1 << 9);
  m ^= (1 << 8);
  m ^= (1 << 9);
  m |= (1 << 9); // double precision
  asm ("fldcw %0" : : "m" (*&m) );
  asm ("fwait");

  m = 1 << 12;
  asm ("ldmxcsr %0" : : "m" (*&m) );
}
#endif