Why aren't unsigned OpenMP index variables allowed?

Question

I have a loop in my C++/OpenMP code that looks like this:

#pragma omp parallel for
for(unsigned int i=0; i

Answer 1

The Microsoft C/C++ Compiler 12.0 integrated with Visual Studio 2013 still only support OpenMP 2.5 and doesn't allow unsigned int for the loop counter.

GCC support OpenMP 3.0 since its version 4.4 and allows unsigned int for the loop counter.