Question

Is there a good reason why this program compiles under GCC even with the -ansi and -pedantic flags?

#include <cmath>

int main (int argc, char *argv [])
{
     double x = 0.5;

     return static_cast<int>(round(x));
}

This compiles clean (no warnings, even) with g++ -ansi -pedantic -Wall test.cpp -o test.

I see two problems:

1. round() shouldn’t be available to C++ in ISO-conformant mode (since it comes from C99)
2. Even if round() were available in this case, it should only be so from the std namespace

Am I wrong?

Answer 1

This is a bug. It’s been around for a surprisingly long while. Apparently, there has not been enough of a collective desire to fix it. With a new version of C++ just around the corner which will adopt the C99 functions from math.h, it seems unlikely it will ever be fixed.