使用C宏包装函数（带有重命名）

Question

I am trying to define a function using macros that would actually wrap an existing function into an other one with a prefix. Let's say for example:

int   f1(int a, void *b, char c) { return 1; }
int   f2(void *a) { return 1; }
void  f3(void *a, int b) {}
void  f4() {}

#define WRAP(prefix, f) // do something
WRAP(a, f1) or WRAP(a,f1,int,void*,char) or WRAP(a,f1,int,a,void*,b,char,c)

This should produce something like:

int a_f1(int a, void *b, char c);
int a_f1(int a, void *b, char c) { return f1(a,b,c); }

I'm trying to do it so it could work with any of f1, f2, f3 or f4. If anyone has an idea on how to do that I would be really thanksfull.

Answer 1

If you can be bothered to specify the return type and parameters of the wrapped function, Boost.Preprocessor has you covered:

#include <boost/preprocessor/tuple/to_seq.hpp>
#include <boost/preprocessor/seq/for_each_i.hpp>
#include <boost/preprocessor/comma_if.hpp>

#define WRAP_declare_param(r, data, i, paramType) \
    BOOST_PP_COMMA_IF(i) paramType _ ## i

#define WRAP_forward_param(r, data, i, paramType) \
    BOOST_PP_COMMA_IF(i) _ ## i

#define WRAP_seq(prefix, retType, function, argSeq) \
    inline retType prefix ## function ( \
        BOOST_PP_SEQ_FOR_EACH_I(WRAP_declare_param, ~, argSeq) \
    ) { \
        return function( \
            BOOST_PP_SEQ_FOR_EACH_I(WRAP_forward_param, ~, argSeq) \
        ); \
    }

#define WRAP(prefix, retType, function, ...) \
    WRAP_seq(prefix, retType, function, BOOST_PP_TUPLE_TO_SEQ((__VA_ARGS__)))

Which lets you write the following:

// Declared somewhere...
int foo(float, double);

WRAP(p_, int, foo, float, double)
//   ^^                          Prefix
//       ^^^                     Return type
//            ^^^                Function
//                 ^^^^^^^^^^^^^ Parameter types

Which expands to:

inline int p_foo ( float _0 , double _1 ) { return foo( _0 , _1 ); }