Why is this simple program in C crashing (VS VS pointer)

Question

I have two files:

In file 1.c I have the following array:

char p[] = "abcdefg";

In the 0.c file, I have the following code:

#include <stdio.h>

extern char *p; /* declared as 'char p[] = "abcdefg";' in 1.c file */

int main()
{
    printf("%c\n", p[3]);   /* crash */
    return 0;
}

And this is the command line:

gcc  -Wall -Wextra     0.c  1.c

I know what extern char *pit was supposed to be: extern char p[];but I just need to explain why it does not work in this particular case . Although it works here:

int main()
{
    char a[] = "abcdefg";
    char *p = a;

    printf("%c\n", p[3]);   /* d */
    return 0;
}

Answer 1

Your two examples are not comparable.

In your second example, you have

char a[] = "abcdefg";
char *p = a;

So ais an array, and pis a pointer. Drawing it in photos, it looks like

      +---+---+---+---+---+---+---+---+
   a: | a | b | c | d | e | f | g | \0|
      +---+---+---+---+---+---+---+---+
        ^
        |
   +----|----+
p: |    *    |
   +---------+

And all is well; no problem with this code.

1.c p:

   +---+---+---+---+---+---+---+---+
p: | a | b | c | d | e | f | g | \0|
   +---+---+---+---+---+---+---+---+

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printf("%p\n", p);

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printf("%c\n", p[3]);

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