Real-world advantage of namespace aliases vs defines [closed]

Answer 1

In this particular case, it depends. If using a namespace alias does the trick, by all means prefer it to macros, for all of the usual reasons. But the two do radically different things. You cannot open a namespace using its alias, i.e.:

namespace XYZ_ver1 {}
namespace XYZ = XYZ_ver1;

namespace XYZ {     //  Illegal!
}

This works with a macro; in fact, you can define the macro before the namespace has ever appeared. If you need this, then you need to use a macro.

Answer 2

Generally speaking, the only advantage I see with namespace aliases is that they can be anywhere. Take the following example:

namespace a
{
    namespace that_is_a_great_namespace
    {
        namespace b = that_is_a_great_namespace;
    }
}

namespace that_is_a_great_namespace {}

You won't be able to define a macro that will convert a::that_is_a_great_namespace to a::b with no side effect. Here, that_is_a_great_namespace will also be converted to b. Namespace aliases help to resolve name conflicts in those cases.

However, if you already use #defines and it already works, refactoring your code for such a rare case may not be useful.