Wrapping functions with macros (without renaming) C

Question

Im interested to add in some extra logic around existing function calls, by wrapping them without renaming them. (just for a test).

The existin

Answer 1

For example, lets say I want to check the types on a function call.

A simple case, I want to check that sqrt only takes (int or double), not float.

Here is a method that works OK.

/* add this to a header or at the top of the source-code */
#include 
static typeof(&sqrt) sqrt_wrap = sqrt;
#define sqrt(f) (_Generic((f), int: sqrt_wrap, double: sqrt_wrap))(f)

This works but has some drawbacks.

• Must include , or at least define sqrt since we dont know if the static function is called or not.
• Defines a function all over which may be unused. though __attribute__((__unused__)) works in works in GCC/Clang.
• All output must have access to the function symbol, even if it ends up not using sqrt.

Edit!

---

This does in fact work, the header just needs to be included first (obviously - in retrospect)

#include 
#define sqrt(f) _Generic((f), int: sqrt(f), double: sqrt(f))

Heres a trick to check sqrt isn't called with float and sqrtf isn't called with double

#include 
#define sqrt(X)  _Generic((X), float:  NULL, default: sqrt)(X)
#define sqrtf(X) _Generic((X), double: NULL, default: sqrtf)(X)