Question

I’m trying to write a macro to create user-defined literals out of a regular string literals. The following two lines should create the token "foobar"_literal:

#define AS_LITERAL(TEXT) TEXT ## _literal
AS_LITERAL("foobar");

However, the pre-processor of GCC-4.7 reports the following error:

error: pasting ""foobar"" and "_literal" does not give a valid preprocessing token

How to do that correctly?

Answer 1

It works with an appropriately defined operator "" _literal (using GCC 4.7 as well):

#include <cstdlib>

#define AS_LITERAL(TEXT) TEXT ## _literal

constexpr int operator "" _literal(char const*, std::size_t) { return 0; }

int main() {
    int x = AS_LITERAL("abc");
}