a is defined at scope1.c:1 [in global scope starting at scope1.c:1] as a 
variable with stgclass extern  of type:
  int
f is defined at scope1.c:4 [in global scope starting at scope1.c:1] as a 
extern   function returning
   int
  and taking no arguments
a is defined at scope1.c:5 [in function scope starting at scope1.c:4] as a 
variable with stgclass auto  of type:
  int
a is defined at scope1.c:7 [in block scope starting at scope1.c:7] as a 
variable with stgclass auto  of type:
  int
b is defined at scope1.c:8 [in block scope starting at scope1.c:7] as a 
variable with stgclass auto  of type:
  int
b is defined at scope1.c:10 [in function scope starting at scope1.c:4] as a 
variable with stgclass auto  of type:
  int
b is defined at scope1.c:13 [in global scope starting at scope1.c:1] as a 
variable with stgclass extern  of type:
  int