使用C宏包装函数(带有重命名) [英] Wrapping functions using C macros (with renaming)

问题描述

我正在尝试使用宏定义一个函数，该宏实际上会将现有函数包装到带有前缀的另一个函数中. 举例来说:

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)

这应该会产生类似的内容:

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); }

我正在尝试这样做，以便它可以与f1，f2，f3或f4中的任何一个一起使用. 如果有人对如何做有任何想法，我将非常感谢.

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.

推荐答案

如果您不愿意指定包装函数的返回类型和参数，Boost.Preprocessor将为您服务:

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__)))

可以让您编写以下内容:

Which lets you write the following:

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

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

其中扩展到:

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

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