foo.c: In function ‘main’:
foo.c:4:17: warning: variable ‘x’ set but not used [-Wunused-but-set-variable]
    4 |     int a,b,c,d,x;
      |                 ^
foo.c:15:11: warning: ‘c’ may be used uninitialized [-Wmaybe-uninitialized]
   15 |     d = e /c*f;
      |         ~~^~
foo.c:4:13: note: ‘c’ was declared here
    4 |     int a,b,c,d,x;
      |             ^