使用strcat的分段故障 [英] Segmentation fault using strcat

问题描述

下面是我的code：

char *name, name_log="log-";

从------用户使用'名'-----

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

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

我需要到结束是name_log =登录'name'.log但是我得到一个分段错误：（（我是什么做错了，我怎么能解决这个问题THX

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，如果的这个的是你的code：

For a start, if this is your code:

char *name, name_log="log-";

然后 name_log 是字符，的不是一个字符指针。

then name_log is a char, not a char pointer.

假设这是一个错字，你不能追加到字符串这样。修改字符串是未定义的行为。

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

有关大小可变的字符串，如用户似乎是，这可能是最安全的选择是分配另一个字符串大到足以容纳的结果，是这样的：

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);
}

的的malloc 确保你有足够的空间来完成所有的字符串操作安全，足够的字符为三个组成部分加一个空终止符。

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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