Thread: parsing of individual arguments in a C macro

I've searched around, and have yet to find an example, so I'm thinking maybe it can't be done.

What I want to do is parse an individual argument, like x, passed to a macro.

For instance,

Code:

#define PROTO(x) ........    // <-- my macro 
.
.
.
PROTO(static int foo(char *)) ;    // a function prototype, wrapped inside a macro.

I want to be able to break x apart into each token, and beyond that, be able to recognize that foo is a function name by the placement of the token after the return type (which might be a pointer), and the fact that there is a left paren at the end of it.

Can this be done with the C macro facility? Basically, I want to substsring x and compare the substringed values to constants.

My overall objective is to generate 2 function prototypes from different compilation units.

In one CU, I just want the standard function prototype to be output:

Code:

static int foo(char *) ;

which is done by merely coding:

Code:

#define PROTO(x) x

However, I also want the following function prototype generated based on other environment characteristics:

Code:

int (* foo)(char 8) ;

In short, the static modifier will be dropped and the function name foo will be converted to function pointer foo.

If this can't be done with the Macro facility, I have already worked out how to do this in an ugly way, by comma-separating the tokens:

Code:

#define PROTO(w,x,y,z) w x y ## z  

or 

#define PROTO(w,x,y,z)  x (* y) ## z 
PROTO(static, int, foo, (char *)) ;

and this works fine, but it's kinda/sorta convoluted due to the addition of the commas.

Your "ugly" way is the only way.

Thank you John.c.

The problem is that there is no way to run C code at the preprocessor stage, and the preprocessor itself doesn't have any string processing capability built in, let alone a "de-stringify" operator to turn the results back into tokens.

The gcc preprocessor (cpp) is described here:
Top (The C Preprocessor)

@aghast, you should post your source for this information. Presumably this or similar:
How to parse tokens separated by whitespace in C++ preprocessor? - Stack Overflow
I assume the typeof idea is actually yours. Nice one.

Thanks christop. I normally use assembler, and in the assembler I use, this task would be child's play in the macro facility.