Thread: regarding "initializer element is not constant"

why do i get this error
test.c:6: warning: initializer element is not constant
test.c:6: warning: (near initialization for ‘len’)

when i compile this with "len" as a global int (as shown). It doesn't happen if "len" is localized within main().

Code:

  1 #include <string.h>
  2 #include <stdio.h>
  3 
  4 #define this "that"
  5 
  6 int len = strlen(this);
  7 int main () {
  8         printf("%d\n", len);
  9 }