使用 strcat 的分段错误 [英] Segmentation fault using strcat

问题描述

这是我的代码:

char *name, name_log="log-";

------从用户那里得到名字"-----

------getting 'name' from user-----

strcat(name_log, name);
char ext[] = ".log";
strcat(name_log, ext);

我最终需要的是 name_log = "log-'name'.log" 但我得到一个分段错误错误:((.我做错了什么，我该如何解决它?谢谢

What i need to end up with is name_log = "log-'name'.log" but Im getting a segmentation fault error :((. What am I doing wrong and how can I fix it ? Thx

推荐答案

首先，如果 this 是您的代码:

For a start, if this is your code:

char *name, name_log="log-";

那么 name_log 是 char， 不是 char 指针.

then name_log is a char, not a char pointer.

假设这是一个错字，你不能像这样附加到字符串文字.对字符串文字的修改是未定义的行为.

Assuming that's a typo, you cannot append to string literals like that. Modifications to string literals are undefined behaviour.

对于可变大小的字符串，就像 user 看起来那样，可能最安全的选择是分配另一个足够大的字符串来保存结果，例如:

For a variable sized string, as user appears to be, probably the safest option is to allocate another string large enough to hold the result, something like:

char *name, *name_log = "log-", *ext = ".log";
// Do something to allocate and populate name
char *buffer = malloc (strlen (name_log) + strlen (name) + strlen (ext) + 1);
if (buffer == NULL) {
    // Out of memory.
} else {
    strcpy (buffer, name_log);
    strcat (buffer, name);
    strcat (buffer, ext);
    // Do something with buffer.
    free (buffer);
}

malloc 确保您有足够的空间来安全地执行所有字符串操作，三个组件有足够的字符加上一个空终止符.

The malloc ensures you have enough space to do all the string operations safely, enough characters for the three components plus a null terminator.

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