Reversing C++ foo(MyClass &) vs foo(const MyClass &)

Question

Suppose I want to reverse some binary, will I be able to tell the difference between:

int foo(MyClass &) { ... }

and

int foo(const MyClass &) { ... }

Assuming the code compiled fine, there would be no evidence of the const qualifier whatsoever, right? I used the following code to test it:

class Point { public: int x=6; int y=8; };
int foo(const Point &p){ return p.x+p.y; }
int main(int argc, char **argv)
{
    Point p;
    return foo(p);
}

Then compiled with -g and -O0 and dumped:

$ gcc -g -O0 main.cpp -o main
$ objdump -D ./main | grep "foo"
000000000000066a <_Z3fooRK5Point>:
 6b6:   e8 af ff ff ff          callq  66a <_Z3fooRK5Point>

When I examine the relevant lines it seems the const indeed vanished.

You probably would be able to, by the function's mangled name. No guarantees of course — StoryTeller - Unslander Monica, Jun 17 '20 at 08:52
suppose you have both overloads then there must be evidence of the `const` somehow — 463035818_is_not_an_ai, Jun 17 '20 at 08:53
The const didn't vanish in `_Z3fooRK5Point` - That K is for const — StoryTeller - Unslander Monica, Jun 17 '20 at 09:09
@StoryTeller-UnslanderMonica can you provide reference for the mangled naming convention(s)? — OrenIshShalom, Jun 17 '20 at 09:14
I can't, my experience is anecdotal. But since `c++filt` exists, you can probably start at its source code to get at *some* reference. — StoryTeller - Unslander Monica, Jun 17 '20 at 09:16
Downvoter please explain, this is a valid question with a simple enough answer suggested in the comments. — OrenIshShalom, Jun 17 '20 at 09:24

score 0 · Answer 1 · answered Jun 17 '20 at 09:23

0

Just pasting @StoryTeller-UnslanderMonica's answer for completeness:

$ c++filt _Z3fooRK5Point
foo(Point const&)

answered Jun 17 '20 at 09:23

OrenIshShalom

5,974
9
37
87

Reversing C++ foo(MyClass &) vs foo(const MyClass &)

1 Answers1