Question

Will the compiler produce the same code for both of these statements?

foo1(int* val){(*val)++;}

foo2(int &val){val++;}

Will it simply write a pointer into the parameter part of foo’s stack frame? Or, in the second case, will the callers’ and foos’ stack frames somehow overlap such that the callers’ local variable takes the same memory on the stack as the parameter for foo?

Answer 1

The stacks cannot be made to overlap.

Consider that the argument could be a global, a heap object, or even if stored in the stack it could be not the very last element. Depending on the calling convention, other elements might be placed in between one stack frame and the parameters passed into the function (i.e. return address)…

And note that even if nothing was added in the stack, the decision cannot be made while compiling the function, but rather when the compiler is processing the calling function. Once the function is compiled, it will not change depending on where it is called from.