Question

Below is my code

#import <stdio.h>
#import <string.h>

int main(int argc, const char *argv[])
{
    char *str = "First string";
    char *str2 = "Second string";
    
    strcpy(str, str2);
    return 0;
}

It compiles just fine without any warning or errors, but when I run the code I get the error below

Bus error: 10

What did I miss ?

Answer 1

For one, you can’t modify string literals. It’s undefined behavior.

To fix that you can make str a local array:

char str[] = "First string";

Now, you will have a second problem, is that str isn’t large enough to hold str2. So you will need to increase the length of it. Otherwise, you will overrun str – which is also undefined behavior.

To get around this second problem, you either need to make str at least as long as str2. Or allocate it dynamically:

char *str2 = "Second string";
char *str = malloc(strlen(str2) + 1);  //  Allocate memory
//  Maybe check for NULL.

strcpy(str, str2);

//  Always remember to free it.
free(str);

There are other more elegant ways to do this involving VLAs (in C99) and stack allocation, but I won’t go into those as their use is somewhat questionable.

---

As @SangeethSaravanaraj pointed out in the comments, everyone missed the #import. It should be #include:

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