Getting error: Stack around the variable was corrupted

Question

运行以下程序，但出现

错误

Run-Time Check Failure #2 - Stack around the variable 'unzip' was corrupted

什么会导致错误？下面是我的代码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void fmuUnzip() {
  char fmuFileName[100], path[100],strFinal[100];
  char unzip[]="winzip32 -e -o -j";
  printf("Enter fmuFileName\n");
  gets(fmuFileName);

  printf("Enter path of the fmuFileName\n");
  gets(path);
  strcat(unzip," ");
  strcat(unzip,fmuFileName);
  strcat(unzip," ");
  strcat(unzip,path);
}

void fmuLoad() {
  fmuUnzip();
}

int main(int argc,char* argv[]) {
 fmuLoad();
}

Answer 1

这里的问题是（是）

strcat(unzip," ");   //problem starts here itself
strcat(unzip,fmuFileName);
strcat(unzip," ");
strcat(unzip,path);

因为，没有足够的内存来保存连接的字符串。本质上，您正在超出分配的内存并调用 undefined behaviour.

当您定义一个未指定大小的数组并使用字符串对其进行初始化时，数组的有效大小计算为字符串的长度加上空终止符的长度。尝试 "cat" 到那是内存溢出。

来自strcat()的man page（强调我的）

The strcat() function appends the src string to the dest string, overwriting the terminating null byte ('[=15=]') at the end of dest, and then adds a terminating null byte. The strings may not overlap, and the dest string must have enough space for the result. If dest is not large enough, program behavior is unpredictable; ....

解法：

定义一个足够大的目标数组来容纳连接的字符串，当然包括终止空值。

也就是说，gets() ~~纯粹是邪恶的~~ 非常危险，因为它存在缓冲区溢出问题。您可能想改用 fgets()。

Answer 2

在你的情况下 unzip[]="winzip32 -e -o -j"; 有 space 仅用于你的初始字符串，17 个字符 + 空终止符。然后你的变量没有空间用指令添加字符：

strcat(unzip," ");
strcat(unzip,fmuFileName);
strcat(unzip," ");
strcat(unzip,path);

您可以更改为：

void fmuUnzip()
{
   char fmuFileName[100], path[100],strFinal[100];
   printf("Enter fmuFileName\n");
   gets(fmuFileName);

   printf("Enter path of the fmuFileName\n");
   gets(path);
   char *unzip = malloc(17+1+strlen(fmuFileName)+strlen(path)+1);
   strcpy(unzip, "winzip32 -e -o -j");
   strcat(unzip," ");
   strcat(unzip,fmuFileName);
   strcat(unzip," ");
   strcat(unzip,path);
}

Getting error: Stack around the variable was corrupted

Getting error: Stack around the variable was corrupted

c

runtime-error