How do I show the value of a #define at compile time in gcc
To display macros which aren't strings, stringify the macro:
#define STRINGIFY(s) XSTRINGIFY(s)#define XSTRINGIFY(s) #s#define ADEFINE 23#pragma message ("ADEFINE=" STRINGIFY(ADEFINE))If you have/want boost, you can use boost stringize to do it for you:
#include <boost/preprocessor/stringize.hpp>#define ADEFINE 23#pragma message ("ADEFINE=" BOOST_PP_STRINGIZE(ADEFINE))
I'm not sure if this will do what you want, but if you're only interested in this to debug the occasional macro problem (so it's not something you need displayed in a message for each compile), the following might work for you. Use gcc's -E -dD option to dump #define directives along with preprocessing output. Then pipe that through grep to see only the lines you want:
// test.c#include <stdlib.h>#include <stdio.h>#define ADEFINE "23"#include <string.h>int main(int argc, char *argv[]){#undef ADEFINE#define ADEFINE 42 return 0;}The command gcc -E -dD -c test.c | grep ADEFINE shows:
#define ADEFINE "23"#undef ADEFINE#define ADEFINE 42