/in/foo.c: In function 'main':
/in/foo.c:6:2: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'a'
  a=10,b=20
  ^
/in/foo.c:8:19: error: 'sum' undeclared (first use in this function)
     printf("%d\n",sum);
                   ^~~
/in/foo.c:8:19: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:5:6: warning: unused variable 'a' [-Wunused-variable]
  int a,b
      ^