Linux分段错误

Question

When I run this program I get segmentation fault, and I could not find it's origin. I don't know how to deal with it. Could you help me?

This is my code.

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

    static int func(int argc, char * argv[])
    {
      char msg[500]="sdfsdf";

      argv[0]="sdf grgrg";

      printf("%s",argv[0]);

      argv[0]='\0';

      strcpy(argv[0],msg);

      printf("%s",argv[0]);

      return 0;
    }

    int main(int argc, char* argv[])
    {
      func(argc, argv);
      //printf("sdfasf");
    }

Answer 1

Let's focus on these lines.

argv[0]='\0';
strcpy(argv[0],msg);

It's irrelevant that this is argv[0] , so I'll introduce a variable:

char *var = '\0';
strcpy(var, msg);

Then, recall that '\\0' is an integer literal with value zero, so when it is assigned to a pointer variable it becomes a null pointer:

char *var = NULL;
strcpy(var, msg);

We can inline the variable:

strcpy(NULL, msg);

Whoops! Don't do that. That will crash, or worse--it might not crash.