I m working on a programming language that uses C++ as it s target language for now. I m hitting an exceptionally strange backtrace.

#1  0x08048d09 in factorial (n=0x8052160) at ir.cpp:35
35      shore::builtin__int * __return = NULL;
(gdb) bt
#0  shore::builtin__int::__mul__ (this=0x8052160, other=0x8052288) at /home/alex/projects/shore/shore/runtime/int.h:36
#1  0x08048d09 in factorial (n=0x8052160) at ir.cpp:35
#2  0x08048cfa in factorial (n=0x80520b8) at ir.cpp:35
#3  0x08048cfa in factorial (n=0x8052018) at ir.cpp:35
#4  0x08048d6f in main () at ir.cpp:43

Specifically it appears that declaring the type of return is somehow triggering the __mul method on builtin__int to be called, and I have no idea why. builtin__int looks like:

#ifndef _SHORE_INT_H
#define _SHORE_INT_H

#include "gc.h"


namespace shore {
    class builtin__int : public shore::Object {
        public:
            // Some day this will be arbitrary percision, but not today.
            long long value;

            static builtin__int* new_instance(long long value_) {
                builtin__int* val = new builtin__int(value_);
                shore::GC::register_object(val);
                return val;
            }

            builtin__int(long long value_) {
                this->value = value_;
            }

            builtin__bool* __eq__(builtin__int* other) {
                return builtin__bool::new_instance(this->value == other->value);
            }

            builtin__int* __add__(builtin__int* other) {
                return builtin__int::new_instance(this->value + other->value);
            }

            builtin__int* __sub__(builtin__int* other) {
                return builtin__int::new_instance(this->value - other->value);
            }

            builtin__int* __mul__(builtin__int* other) {
                return builtin__int::new_instance(this->value * other->value);
            }
    };
}
#endif

Any ideas as to what on earth is compelling C++ to call the mul method?

EDIT: Added the source of ir.cpp

#include "builtins.h"
#include "frame.h"
#include "object.h"
#include "state.h"
std::vector < shore::Frame * >shore::State::frames;
shore::GCSet shore::GC::allocated_objects;
class
    factorial__frame:
    public
    shore::Frame {
  public:
    shore::builtin__int *
    n;
    shore::GCSet
    __get_sub_objects() {
    shore::GCSet s;
    s.
    insert(this->n);
    return
        s;
}};
class
    main__frame:
    public
    shore::Frame {
  public:
    shore::GCSet
    __get_sub_objects() {
    shore::GCSet s;
    return
        s;
}};
shore::builtin__int * factorial(shore::builtin__int * n)
{
    shore::builtin__int * __return = NULL;
    factorial__frame frame;
    shore::State::frames.push_back(&frame);
    frame.n = NULL;
    frame.n = n;
    if (((frame.n)->__eq__(shore::builtin__int::new_instance(0)))->value) {
    __return = shore::builtin__int::new_instance(1);
    shore::GC::collect();
    shore::State::frames.pop_back();
    return __return;
    }
    __return =
    (frame.n)->
    __mul__(factorial
        ((frame.n)->
         __sub__(shore::builtin__int::new_instance(1))));
    shore::GC::collect();
    shore::State::frames.pop_back();
    return __return;
}
int
main()
{
    main__frame     frame;
    shore::State::frames.push_back(&frame);
    builtin__print(factorial(shore::builtin__int::new_instance(3)));
    shore::State::frames.pop_back();
}