Expand macro inside string literal

问题:

What I'm trying to do is to #define a macro:

#define a(2)

and later use it inside a string literal: string = "a";.

I want that string to be interpreted not as string but to get the value of a, i.e. 2. I didn't succeed, can anybody help?

回答1:

#define STRINGIFY2(X) #X
#define STRINGIFY(X) STRINGIFY2(X)
#define A 2

Then STRINGIFY(A) will give you "2". You can concatenate it with other string literals by putting them side by side.

"I have the number " STRINGIFY(A) "." gives you "I have the number 2.".

回答2:

No, you cannot do macro expansion INSIDE string literals (i.e. having the preprocessor to look inside literals for macros to expand).

You can have a macro expansion to produce a string literal starting with the stringify operator (#). But that's a different thing.