C Preprocessor, Stringify the result of a macro

c-preprocessor stringification
almosnow picture almosnow · Aug 5, 2010 · Viewed 25.2k times · Source

I want to stringify the result of a macro expansion.

I've tried with the following:

#define QUOTE(str) #str
#define TEST thisisatest
#define TESTE QUOTE(TEST)

And TESTE gets expanded to: "TEST", while I'm trying to get "thisisatest". I know this is the correct behavior of the preprocessor but can anyone help me with a way to achieve the other one?

Using TESTE #TEST is not valid
Using TESTE QUOTE(thisisatest) is not what I'm trying to do

Answer

Steve Jessop picture Steve Jessop · Aug 5, 2010

Like this:

#include <stdio.h>

#define QUOTE(str) #str
#define EXPAND_AND_QUOTE(str) QUOTE(str)
#define TEST thisisatest
#define TESTE EXPAND_AND_QUOTE(TEST)

int main() {
    printf(TESTE);
}

The reason is that when macro arguments are substituted into the macro body, they are expanded unless they appear with the # or ## preprocessor operators in that macro. So, str (with value TEST in your code) isn't expanded in QUOTE, but it is expanded in EXPAND_AND_QUOTE.

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