`testl` eax 对 eax? [英] `testl` eax against eax?

问题描述

我正在尝试理解一些程序集.

I am trying to understand some assembly.

汇编如下，我感兴趣的是testl这一行:

The assembly as follows, I am interested in the testl line:

000319df  8b4508        movl   0x08(%ebp), %eax  
000319e2  8b4004        movl   0x04(%eax), %eax  
000319e5  85c0          testl  %eax, %eax  
000319e7  7407          je     0x000319f0  

我试图理解 %eax 和 %eax 之间的 testl 点?我认为这段代码的具体内容并不重要，我只是想了解测试本身 - 值不总是正确的吗?

I am trying to understand that point of testl between %eax and %eax? I think the specifics of what this code isn't important, I am just trying to understand the test with itself - wouldn't the value always be true?

推荐答案

它测试 eax 是否为 0，或高于，或低于.在这种情况下，如果 eax 为 0，则进行跳转.

It tests whether eax is 0, or above, or below. In this case, the jump is taken if eax is 0.

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