[LLVMdev] Counting pointers to functions

[guyadini]

Hi all,

I'm trying to write an LLVM pass which would determine whether there is any
pointer which ever points to a function. I couldn't figure out if there is
any existing pass which does something of the kind (maybe some analysis pass
which I'm not aware of?).

Of course, I could just iterate over all values, and check whether they
point to functions (as in a similar recent post). However, this will not
always be sufficient - for example, consider the following C code:

#include "stdio.h"

int foo(){
	printf ("Reached function foo\n");
	return 0;
}
int bar(){
	printf("Reached function bar\n");
	return 1;
}

int main(){
	int (*f_ptr)() = &foo;
	(*f_ptr)();
	int diff = (int)&bar- (int)&foo;
	f_ptr = (int (*)()) ( (int)f_ptr + diff);
	(*f_ptr)();
	
	
	return 0;
	
}

This code changes f_ptr from pointing at the function foo to pointing at the
function bar, by explicitly advancing the pointer by the difference in
memory addresses between them.

What can I do to catch that kind of behavior?

Thanks for the help (as usual),
Guy
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