Expand C/C++ function macros without preprocessor

Question

How would I test/expand all the function macros, in a C/C++ file, without running it through a preprocessor? For example, is there a program or method which would change this:

#include <iostream>
#define AAA(a) cout << "function "  << a << endl
using namespace std;
int main(){
AAA(12);
}

into this?

#include <iostream>
using namespace std;
int main(){
cout << "function " << 12 << endl;
}

I don't want to run through preprocessor because all the includes in the files make the "gcc -E <>" output really ugly, I just want a couple simple macro expansions without all the overhead.

Answer 1

No, it's not possible. Your included headers could include macros that you want to expand in the body, for example. Or did you mean to not expand any macros that come from headers? The preprocessor has absolutely no way of distinguishing what you want from what you don't want in this case.

If you know in advance this is not the case, then I recommend simply writing a script to remove the includes and then run that through the preprocessor.

Answer 2

I heard all possible negative answers on the topic:

• macros can only be expanded not evaluated
• processor should parse also include files
• nested macros can be over-complicated
• conditional preprocessing can be tricky
• macros are evil just avoid them
• etc etc....

They are all true, but IMO they collide with the reality of everydays programming.

In fact, working on old C project where macros were mostly simply used as functions this became of crucial importance for me. Generating all preprocessed files with /P works but is overkilling and time taking. I just needed a tool that expands a simple macro defined a few lines above or at maximum in other file.

How to do that?

1 Onl,inux simply use GDB and his expand macros capabilities 2 On windows I use https://www.jetbrains.com/resharper-cpp/ integrated into Visual Studio

So, Yes, in a practical sense, it is possible.