问题描述
我正在为x86编写Lisp编译器。我一直在尝试调试它，因为对于某些变量声明，它会产生错误的输出代码。这是我给它的代码：
(define y (+ 1 2))
(define x 6)
(display x)
我期望输出为6。但是，它输出为零。我将其范围缩小到下面的代码。
我正在MacOS上组装GAS：
gcc -masm=intel overflow_q.asm
.global _main
.text
_main:
push 1 # arg 2 for proc +
push 2 # arg 1 for proc +
pop rsi # begin plus
pop rdi
add rdi,rsi # end plus
push rdi # for the caller of +
pop rax # get result in rax
mov [y + rip],rax # put computed value of 3 into y
mov rsi,[x + rip] # put value of x,6,into rsi
/*
I have not included the code for the call to "display"
because it's irrelevant - and the program still fails
in the same way without it
*/
/*
The bug:
RSI turns out to be zero here! Why is that happening?
I kNow this given the exit code returned from running it.
*/
mov rdi,rsi
mov rax,0x2000001
syscall
.data
y:
.long 0 # initialize with a value of zero
x:
.long 6
解决方法
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