Creating a C++ namespace in header and source (cpp)

Question

Is there any difference between wrapping both header and cpp file contents in a namespace or wrapping just the header contents and then doing using namespace

Answer 1

If you're attempting to use variables from one to the other, then I'd recommend externalizing them, then initializing them in the source file like so:

// [.hh]
namespace example
{
   extern int a, b, c;
}
// [.cc]
// Include your header, then init the vars:
namespace example
{
   int a, b, c;
}
// Then in the function below, you can init them as what you want: 
void reference
{
    example::a = 0;
}