Passing a template which requires a comma to a single-argument macro

Question

I have some code that essentially condenses down to

#define FOO(a)
FOO(std::map);

But it emits a compile error (too many ac

Answer 1

The preprocessor will only treat unparenthesised commas as a macro argument separator. So what you can do is rewrite std::map into something that has parentheses around it. A simple one might be decltype(std::map()).