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Editorial Team
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Asked: 2026-06-12T01:52:29+00:00

I would like to print a macro value (expand the macro) in the #warning

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I would like to print a macro value (expand the macro) in the #warning directive.

For example, for the code:

#define AAA 17
#warning AAA = ???

The desired compile-time output would be 

warning: AAA = 17

What do I use for ???, or, how do I augment the code?

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1 Answer

  1. Editorial Team

    You can use the preprocessor directive #pragma message.

    Example:

    #define STR_HELPER(x) #x
#define STR(x) STR_HELPER(x)

#define AAA 123
#pragma message "content of AAA: " STR(AAA)

int main() { return 0; }

    The output may look like this:

    $ gcc test.c
test.c:5:9: note: #pragma message: content of AAA: 123
 #pragma message("content of AAA: " STR(AAA))
         ^

    For reference:

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