[英]Tiny C Compiler: “error: unknown opcode 'jmp'”
Given this code: 给出以下代码:
int main(void)
{
__asm volatile ("jmp %eax");
return 0;
}
32-bit TCC will complain with: 32位TCC会抱怨:
test.c:3: error: unknown opcode 'jmp'
but the 64-bit version will compile just fine. 但是64位版本可以正常编译。
What's the problem with the 32 bit code? 32位代码有什么问题?
The solution is to simply add a star (*) before the register, like this: 解决方案是在寄存器之前简单地添加一个星号(*),如下所示:
__asm volatile ("jmp *%eax");
I'm not exactly sure what the star means. 我不确定这颗星是什么意思。 According to this SO post:
根据此 SO帖子:
The star is some syntactical sugar indicating that control is to be passed indirectly, by reference/pointer.
星号是某种语法糖,指示控制权将通过引用/指针间接传递。
As for why it works with 64-bit TCC, I assume that it's a bug; 至于为什么它可以与64位TCC一起使用,我认为这是一个错误。 64-bit GCC complains with
Error: operand type mismatch for 'jmp'
, as it should. 64位GCC会
Error: operand type mismatch for 'jmp'
,应该这样。
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