c - 程序收到信号 : “EXC_BAD_ACCESS” ?

Question

我正在使用 XCode 在 C 中制作一个命令行程序。运行该程序时，它最初会执行它应该执行的操作(向我询问文件路径)。但是，当我输入有效且现有的文件路径时，它会出现以下错误:

Program received signal:  “EXC_BAD_ACCESS”. sharedlibrary apply-load-rules all (gdb)

我的程序中有两个警告，都与函数 strcat 有关。警告是:

warning: implicit declaration of function 'strcat'

和

warning: incompatible implicit declaration of built-in function 'strcat'

我想知道为什么我的程序不能正常执行。

谢谢，迈克

我的代码贴在下面:

#include "stdlib.h"
int main (void)
{
   char *string1;
   printf("Type in your file path: ");
   scanf("%s", string1);
   char *string2 = "tar czvf YourNewFile.tar.gz ";
   strcat(string2, string1);
   system(string2);
}

也许这与分配字符有关？

Answer 1

你忘记为string1分配空间，scanf不会为你分配内存，你必须自己做。此外， string2 指向不可写的内存，它没有足够的空间将 string1 附加到它，所以你的 strcat 甚至会溢出如果你有 char string2[] = "tar czvf YourNewFile.tar.gz ";。

这是一个更接近您真正想要的东西的注释版本:

#include <stdio.h>  /* printf, sprintf, fgets */
#include <string.h> /* strcat, strlen */
#include <stdlib.h> /* malloc */

#define TAR "tar czvf YourNewFile.tar.gz"

int main(void) {
    char path[100] = { 0 };  /* Initialize to all 0 bytes.           */
    char *cmd;               /* We'll allocate space for this later. */
    int   len;

    printf("Type in your file path: ");
    fgets(path, sizeof(path), stdin);   /* Read at most 100 characters into path */

    /*
     * Remove the trailing newline (if present).
     */
    len = strlen(path);
    if(path[len - 1] == '\n')
        path[len - 1] = '\0';

    /*
     * Allocate room for our command. 
     */
    cmd = malloc(
          strlen(TAR)   /* Room for the base tar command.         */
        + 1             /* One more for the space.                */
        + strlen(path)  /* Room for the path we read.             */
        + 1             /* One more for the final nul terminator. */
    );

    /*
     * You could also use a bunch of strcpy and strcat stuff for
     * this but sprintf is less noisy and safe as long as you've
     * properly allocated your memory.
     */
    sprintf(cmd, "%s %s", TAR, path);

    /*
     * This is vulnerable to unpleasant things in `path` (such as spaces,
     * &, >, <, ...) but this will do as a learning exercise. In real life
     * you'd probably want to use fork and exec for this to avoid the  
     * interface issues with the shell.
     */
    system(cmd);  

    /*
     * Free the memory we allocated.
     */
    free(cmd);

    /*
     * You need a return value because of "int main(...)". Zero is
     * the standard "all's well" return value.
     */
    return 0;
}

如果我犯了任何差一错误，请有人告诉我。

您可以在上面的over here中找到函数的引用资料.