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Question

I have an C++ program. Somewhere in the program (hard to reproduce, but reproduceable) a caclculation results in a float beeing set to a NaN. Since a floating point operation involving a NaN results in a NaN, this spreads fast.

Is there any way I can setup the compiler (gcc 4.4) or the debuger (gdb) to stop when a floating point operation results in a NaN? That would be extremely useful.

Thanks! Nathan

PS: It might matter: I am working under ubuntu linux 10.10.

Answer

You can use feenableexcept like so:

#include <cfenv>
#include <iostream>
int main(){
  // Values at: https://cplusplus.com/reference/cfenv/FE_OVERFLOW/
  feenableexcept(FE_INVALID);
  for(int i=0;i<10;i++){
    std::cout<<(i/0.)<<std::endl;
  }
  return 0;
}