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: