Is NASM inconsistent or am I just missing an obvious fact with CMP of immediate?
assembly, nasm, x86-64
Solution
There's no `CMP r/m64,imm64`. There's `CMP r/m64,imm32`, where `imm32` is sign-extended to 64 bits. Which works fine for `0xfffffffffffffff1`, because `0xfffffff1` sign-extended to 64 bits is `0xfffffffffffffff1`. But `0x1000a8a9` sign-extended to 64 bits is `0x000000001000a8a9`, which differs from the value you wanted to compare against.
You could overcome this e.g. by loading the immediate into a register first:
mov rax, INTEGER
cmp qword [rdi+FRTType.type], rax
Problem
The "warning: signed dword immediate exceeds bounds" is the bane of my existence at the moment as it appears to be inconsistent or I am just not seeing an obvious fact. I have the following structure declared: ``` struc FRTType .class resq 1 ; Class .type resq 1 ; Type endstruc ``` I have the following assigns: ``` %assign TYPE_SCALAR 0xfffffffffffffff1 %assign INTEGER 0xffffffff1000a8a9 ``` And in a function I have: ``` cmp qword [rdi+FRTType.class], TYPE_SCALAR ; This works fine jne .exception cmp qword [rdi+FRTType.type], INTEGER ; THIS PRODUCES WARNING ``` I know I can `mov rax, INTEGER` and then do the compare but that seems unneeded given the first compare has no problem.