strcpy 和 strcat 有时会出现问题
你好，我有一个像下面这样的代码
char *str ;
strcpy(str, "\t<");
strcat(str, time);
strcat(str, ">[");
strcat(str, user);
strcat(str, "]");
strcat(str, "(");
strcat(str, baseName);
strcat(str, ") $ ");
printf("\String is now: %s\n", str);
这段代码似乎可以工作，但是当我使用 XCode 分析函数时，它说“函数调用参数是一个未初始化的值”，而且它有时会导致我的程序崩溃..当我删除它时，它就可以工作好吧……有什么问题吗？谢谢
hello I have a code like the one below
char *str ;
strcpy(str, "\t<");
strcat(str, time);
strcat(str, ">[");
strcat(str, user);
strcat(str, "]");
strcat(str, "(");
strcat(str, baseName);
strcat(str, ") $ ");
printf("\String is now: %s\n", str);
This code seems working but when I use XCode analyse function, it says "Function call argument is an uninitialized value" and also it sometimes causes my program crash.. when I remove it, then it works fine... Whats wrong with that? Thanks
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strcpy和strcat用于将字符串复制并连接到分配的 char 数组。由于 str 未初始化，您正在内存中的某个位置写入，这很糟糕，因为您正在破坏其他数据。它可能在那一刻起作用，但迟早你的程序会崩溃。
声明 str 时应该分配内存：
char str[100];另外，
strcat效率不高，因为它需要搜索字符串末尾才能知道在哪里连接字符。使用 sprintf 会更高效：sprintf(str, "\t<%s>[%s](%s) $ ", time, user, baseName);
最后，如果不能保证生成的字符串适合数组，最好使用 snsprintf。
strcpyandstrcatare used to copy and concatenate strings to an allocated char array.Since
strin not initilized you're writing somewhere in memory and this is bad because you're corrupting other data. It may work at that moment but sooner or later you'll program will crash.You should allocate memory when declaring str:
char str[100];Also,
strcatis not efficient as it needs to search for the string end to know where concatenate chars. Usingsprintfwould be more efficient:sprintf(str, "\t<%s>[%s](%s) $ ", time, user, baseName);Finally, if you can't guarantee the generated string will fit the array, you'd better use snsprintf.
您不分配内存，并且
str未初始化。所有后续写入都是通过指向“某处”的未初始化指针完成的 - 这是未定义的行为。您必须分配（然后释放）足够大的内存来容纳生成的字符串：
You don't allocate memory and you leave
struninitialized. All later writes are done through an uninitialized pointer that points "somewhere" - that's undefined behavior.You have to allocate (and later free) memory large enough to hold the resulting string:
这更加简单并且不会出现缓冲区溢出错误：
This is much simpler and error-free from buffer overflows: