Why can't I use this code to overwrite a string?

Question

Code:

#include \"stdio.h\"
#include \"string.h\"

int main()
{
  char *p = \"abc\";
  printf(\"p is %s \\n\", p);
  return 0;
}

O

Answer 1

Because p points to a read-only memory region (__TEXT segment) which contains the string "abc".

As you strcpy it, a read-only memory region is going to be overwritten, which is illegal. So the kernel will SegFault your program.

If you want writable memory, you need to allocate it on the stack

char p[1024] = "abc";

or on the heap

char* p = malloc(1024);
...
free(p);

or in the __DATA segment (i.e. a global variable)

static char p[1024] = "abc";