Result of calling strcpy is different than expected

Question

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

int main()
{
   char src[]="123456";
   strcpy(src, &src[1]);
   printf("Final copied string : %s\n", src);
}

When I use the Visual Studio 6 Compiler it gives me the expected answer "23456".

How come this program prints "23556" when compiled with gcc 4.7.2?

Answer 1

strcpy(src, &src[1]); is undefined behavior:

C11 §7.24.2.3 The strcpy function

The strcpy function copies the string pointed to by s2 (including the terminating null character) into the array pointed to by s1. If copying takes place between objects that overlap, the behavior is undefined.

By the way, memcpy is similar (but not memmove). See C FAQ: What's the difference between memcpy and memmove.