Placing a preprocessor directive inside a string literal?

Question

I'm trying to use #define to define a string literal (a filepath in this case), but I cannot get the path FROM another #define'd element. In short, I'd like something like this:

#define X /var/stuff
#define Y "X/stuff.txt"

To give me Y as "/var/stuff/stuff.txt". Is this even possible to do? Thanks beforehand.

EDIT: Alternatively, would something like this concat the two literals into one?

#define X "/var/stuff"
#define Y X"/stuff.txt"

Jerry Coffin · Accepted Answer · 2013-02-06T03:40:04.227

3

Not the way you have it, no -- macro replacement does not happen inside string literals.

You can, however, paste together a string from pieces:

#define str(x) #x
#define expand(x) str(x)

#define X /var/stuff
#define Y expand(X) "/stuff.txt"

Quick demo code for this:

#include <iostream>

int main(){
    std::cout << Y;
}

edited Feb 06 '13 at 03:40

answered Feb 06 '13 at 03:35

Jerry Coffin

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So there is no way to make a string literal out of two macros then? – SuperTron Feb 06 '13 at 03:35
@SuperTron yes, but its ugly and involves some multi level preprocessor voodoo – Richard J. Ross III Feb 06 '13 at 03:40
1

@SuperTron: See edited answer. – Jerry Coffin Feb 06 '13 at 03:43
I believe OPs edits would actually work as-is – Karthik T Feb 06 '13 at 03:44
Yes, they sure do :) Thanks! – SuperTron Feb 06 '13 at 03:47
2

Yes -- if you don't mind defining everything as a string literal up-front, then you can just put them next to each other, and the compiler will concatenate them together for you. – Jerry Coffin Feb 06 '13 at 03:49

Placing a preprocessor directive inside a string literal?

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