x86 calling convention: should arguments passed by stack be read-only?

Question

It seems state-of-art compilers treat arguments passed by stack as read-only. Note that in the x86 calling convention, the caller pushes arguments onto the stack and the callee

Answer 1

Actually, I just compiled this function using GCC:

int foo(int x)
{
    goo(&x);
    return x;
}

And it generated this code:

_foo:
        pushl       %ebp
        movl        %esp, %ebp
        subl        $24, %esp
        leal        8(%ebp), %eax
        movl        %eax, (%esp)
        call        _goo
        movl        8(%ebp), %eax
        leave
        ret

This is using GCC 4.9.2 (on 32-bit cygwin if it matters), no optimizations. So in fact, GCC did exactly what you thought it should do and used the argument directly from where the caller pushed it on the stack.