什么是双百分号（%%）在GCC内联汇编吗？ [英] What does a double-percent sign (%%) do in gcc inline assembly?

问题描述

我碰到一个code，看起来像这样来了：

I came across a code that looks like this:

asm volatile (
    # [...]
    "movl $1200, %%ecx;"
    # [...]
);

我知道什么是 MOVL $ 1200，ECX％确实在86。但我对为什么有两个百分比符号混淆。

I know what movl $1200, %ecx does in x86. but I was confused by why there are two percent signs.

推荐答案

GCC内联汇编使用％0％1％2等指输入和输出操作数。这意味着你需要使用两个%%真正的寄存器。

GCC inline assembly uses %0, %1, %2, etc. to refer to input and output operands. That means you need to use two %% for real registers.

勾选此 HOWTO 伟大的信息。

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