You're right, it does add 1 to RDI, but this is exactly what we want. This is x86_64 calling convention, where arguments come on registers, not the stack. On 32

You're right, it does add 1 to RDI, but this is exactly what we want. This is x86_64 calling convention, where arguments come on registers, not the stack. On 32-bit x86 you'd do something like mov eax, 1 add eax, [esp + 4] ret