Question

#include <stdio.h>

int main(void)
{
    char a[100] = "hi";

    strcat(a, a);
    strcat(a, a);

    printf("%s
", a);

    return 0;
}

Answer 1

从C语标准中的strcat下的定义,§7.21.3.1/2

<编码> 如果复制在重复的物体之间发生,则不明确。

我的编篡甚至一次如strcat(a, a);复制了第一个论点末尾关于的第二种论点的第一份性质,然后是第二个论点之后的第二次性质,等等,直到它在第二个论点中遇到为止。

Answer 2

原文:

<><>>>>>

The strcat() and strncat() functions append a copy of the null-terminated
string s2 to the end of the null-terminated string s1, then add a termi-
nating . The string s1 must have sufficient space to hold the
result.

The strncat() function appends not more than n characters from s2, and
then adds a terminating .`

The source and destination strings should not overlap, as the behavior is
undefined.

Answer 3

This is undefined behavior.

如果你在座右边读到每张<条码><>>条/条码>,则在座右边读到<条码>,但与此同时,你在休息时间结束时再读(书面)果园?

Answer 4

I suspect it s because the implementation is overwriting the null byte at the end:

Start: a = {h,i,}
         src^   vdst
next:  a = {h,i,h}
           src^   vdst
next:  a = {h,i,h,i}
             src^   vdst
next:  a = {h,i,h,i,h}
...

由于你夸大了无名词,你的消息来源描述将永远不会结束,而且这种方法将保持复制,直到它努力获得其笔迹和eg。

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