Function Pointer Wrapper Ideas

Function Pointer Wrapper Ideas

If we decide to wrap all function pointer args to external functions, we need to design the wrapper.

Ideas

Creating a new Function for each call to an external function

• The llvm pass can identify Value objects which are function pointers.
• It can also identify if these function pointers are to external functions.
• Once we have this collection of pointers to internal functions passed to external functions, we can create a wrapper for each, with the same type, and create a static member for this function to store the value.
• Then, at the site of the call we simply set the static member to the original argument and pass a pointer to the wrapper to the external function.

For example,

Original code

extern void atexit(void (*f)(void));
void main()
{
    atexit(&f0);
}

New code:

static void (*wrap0_ptr)();
void wrap0()
{
    wrap0_ptr();
}

void main()
{
    wrap0_ptr = &f0;
    atexit(&wrap0);
}