Thread: isnan() and isinf() in C++

If it wasn't optimized, you wouldn't need the volatile temp.

Originally Posted by cpjust

Maybe it would be good to add a #pragma to the C/C++ standard to do something like this:

Code:

#pragma no_optimize_begin
bool myisnan(double var)
{
    volatile double temp = var;
    return temp != temp;
}
#pragma no_optimize_end

By definition, pragmas are compiler and/or operating system specific, and therefore no particular particular pragmas will ever be added to the C/C++ standards.

Actually, C99 has standard pragmas in the form

#pragma STDC pragma_name

However, a no-optimization directive would imply that there is a standard implementation technique for each platform.