CODEWITHSUNDEEP
c
Felipe Lavratti
Felipe Lavratti

Reputation: 2967

How to get a function signature and declare another with the same signature using the preprocessor?

How can I get a function signature and declare another with the same signature using the preprocessor?

I wanted to do something like this:

int function_to_be_copied_from(int arg, int arg2);
FUNC_COPY_SIGNATURE(function_to_be_copied_from, new_function_name)
{
  do_something(arg, arg2);
}

And get this:

int function_to_be_copied_from(int arg, int arg2);
int new_function_name(int arg, int arg2)
{
  do_something(arg, arg2);
}

Gcc extensions are allowed, such as typeof, for example.

I want to create a runtime profiler system, specifically, I need to replace functions using a macro. This macro has got to create a wrapper function that computes the execution time of the replaced function and rename the replaced function.

Upvotes: 3

Views: 130

Answers (1)

anishsane
anishsane

Reputation: 20980

Try below approach:

Create a macro for profiling:

#define profile_me(my_code) ({timer_start_code; my_code timer_stop_code;})
// NOTE: there is no `;` after my_code in macro evaluation
// This helps for profiling any code, having braces. (see Sample_usage2)
// Sample_usage1: profile_me(function_to_be_copied_from(5,10););
// Sample_usage2: profile_me(if(condition){do_something();});

Create a recursive macro for the functions you want to profile:

#define function_to_be_copied_from(...) profile_me \
       (function_to_be_copied_from(__VA_ARGS__);)

Then use the original function normally. The profiling code will be called automatically.

For taking care of the return value:

#define profile_me_int(my_code) ({       \
    int ret;                             \
    timer_start_code;                    \
    ret = my_code                        \
    timer_stop_code;                     \
    ret;                                 \
}) // ret data type is chosen based on function_to_be_copied_from's return type

#define function_to_be_copied_from(...) profile_me_int \
       (function_to_be_copied_from(__VA_ARGS__);)

Upvotes: 2

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