c - strcpy() 和字符串左移给出错误的结果

Question

在某些项目中，我有一段 C 代码运行错误，但仅限于特定的输入字符串。我只编译这一段:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define slength 1000    // max string length
char ss[slength];
int main(void) {
    strcpy(ss, "\"abcdefghijkl\"");
    printf("1 %s\n",ss);
    if (ss[0]=='"') {       // remove quotes
        printf("2 %s\n",ss);
        strcpy(ss, ss+1);   // remove first symbol - quote
        printf("3 %s\n",ss);
        ss[strlen(ss)-1]='\0';  //last symbol
        printf("4 %s\n",ss);
    }
    printf("5 %s\n",ss);
    return EXIT_SUCCESS;
}

结果是

1 "abcdefghijkl"
2 "abcdefghijkl"
3 abcdefhhijkl"
4 abcdefhhijkl
5 abcdefhhijkl

所以我得到的是“abcdefhhijkl”而不是“abcdefghijkl”。我哪里错了？谢谢。

附言我希望我的代码中没有任何多字节/Unicode 字符，但可能需要额外检查。

gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) 
Linux test-i3 3.13.0-63-generic #104~precise1-Ubuntu SMP Tue Aug 18 17:03:00 UTC 2015 i686 i686 i386 GNU/Linux

Answer 1

来自 strcpy(3) 手册:

   The  strings  may  not overlap, and the destination string dest must be
   large enough to receive the copy.  Beware  of  buffer  overruns!   (See
   BUGS.)

你应该使用memmove(3):

    memmove(ss, ss+1, strlen(ss));   // remove first symbol - quote

...而不是...

    strcpy(ss, ss+1);   // remove first symbol - quote