Debug C++ code: Catch first NaN appearance [duplicate]

Question

Is there a simple way to check a C++ code in a debugger for the very first appearance of a NaN value?

Answer 1

The answer is given here: https://stackoverflow.com/a/5394095/1326595

Just include

#include <fenv.h>

and than add the following line to the code:

feenableexcept(FE_INVALID | FE_OVERFLOW);

The debugger is than able to capture the signal and shows the very first occurrence of a NaN.

Answer 2

By IEEE standard the following condition is false for NaN's:

val == val

and you could use it to trigger assert or software breakpoint, but beware of compiler optimizations. Probably, in debug build it would not get optimized away