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Wrapping C/C++ Function Definitions

Sunday, August 20, 2006 by digitalpeer

The following example shows how to wrap function definitions so code can be added to the beginning or end of every function call from one place. The example just counts the number of times the function is called, which is useful for printing a runtime call tree. It can be expanded to time functions calls and generate runtime profiling information if no other means is available. Of course, I don't condone this type of coding. Consider it a proof of concept.

#include <stdio.h>

/**
 * Define a function.
 * 
 * @param ret Function return value.
 * @param name The name of the function.
 * @param params List of parameters with surrounding parenthesis.
 */
#define FUNC(ret, name, params) \
   ret name params \
   { \
      {\
         static unsigned int cnt = 0; \
         printf("%s [%d]\n",__PRETTY_FUNCTION__,cnt++); \
      }

/**
 * End function definition.
 */
#define END }

FUNC(int,myfunc,(int param1,int param2,int param3))
   int x = 0;
   return x++;
END

int main()
{
   myfunc(1,2,3);
   myfunc(1,2,3);
   myfunc(1,2,3);
   return 0;
}

Running the example results in:

 
myfunc [0]
myfunc [1]
myfunc [2]