How do I at compile time undefine a compiler macro using gcc. I tried some compile args to gcc like -D but I can't get to see the "not defined" message.
Thanks
#include <iostream>
#define MYDEF
int main(){
#ifdef MYDEF
std::cout<<"defined\n";
#else
std::cout<<"not defined\n";
#endif
}
You can use the -U option with gcc, but it won't undefine a macro defined in your source code. As far as I know, there's no way to do that.
http://gcc.gnu.org/onlinedocs/gcc-4.4.2/gcc/Preprocessor-Options.html#Preprocessor-Options
The -U options seemed like what you could have needed... but then again you can't override a definition contained in your source code without resorting to more preprocessor directives.