CODEWITHSUNDEEP
c
Felipe Lavratti
Felipe Lavratti

Reputation: 2967

Autogenerating a function wrapper in C

I want to create a function wrapper, with a defined body, that calls the wrapped function.

How can I get from this:

int foo (int arg)
{ 
   do_something(arg);
}

To something equivalent to this:

int foo (int arg)
{
   always_do_this();
   real_foo(arg);
}
int real_foo (int arg)
{ 
   do_something(arg);
}

I must do the transformation automatically and it has to be signature independent and in compile time.

How can I do it?

Upvotes: 4

Views: 177

Answers (2)

Felipe Lavratti
Felipe Lavratti

Reputation: 2967

I had to give up from installing wrapper on function declaration, the solution was to install the wrappers on function call using compound statements. Bellow the two macros I created to do that, one deals with calls returning void, other with any call that returns a value:

#define PROFILE_VOID(call) \
({ \
  hal_time_t stop, start; \
  hal_getTime(&start); \
  call; \
  hal_getTime(&stop); \
  __PROFILE_PRINT(call, hal_secondsElapsed_d(&stop, &start)); \
})

#define PROFILE(call) \
({ \
  typeof(call) __ret; \
  hal_time_t stop, start; \
  __profile_nested_cnt++; \
  hal_getTime(&start); \
  __ret = call; \
  hal_getTime(&stop); \
  __profile_nested_cnt--; \
  __PROFILE_PRINT(call, hal_secondsElapsed_d(&stop, &start)); \
  __ret; \
})

Example of use:

PROFILE_VOID(func_returning_void(arg, arg2)); //Void func
PROFILE(other_funcs());  // Any non void func
PROFILE(x = func(x, y, z));  //Any statement
x = PROFILE(func(x, y, z));  //Same as previous
if (PROFILE(func()) == 0) { } //Inside conditionals
if (PROFILE(func() == 0)) { } //Same as previous

Upvotes: 2

user1551592
user1551592

Reputation:

You can do this with macros, here's a quick example:

#define CREATE_FUNC_WRAPPER(NAME, ARG)      \
    int NAME(ARG arg) {         \
        real_##NAME(arg);       \
    }

int real_foo(int a) {
    printf("real_foo speaking: %d\n", a);
}

CREATE_FUNC_WRAPPER(foo, int)

int main() {
    foo(1);
}

You need to modify it to fit your needs, your question is unclear.

Upvotes: 2

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