/in/foo.c:5:6: warning: return type of 'main' is not 'int' [-Wmain]
 void main()
      ^~~~
/in/foo.c: In function 'main':
/in/foo.c:17:4: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
    for(i=49;a[i]==0;i--) ;
    ^~~
/in/foo.c:18:4: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'for'
    {for(;i>=0;i--)
    ^
/in/foo.c:21:11: warning: 'return' with a value, in function returning void
    return 0;
           ^
/in/foo.c:5:6: note: declared here
 void main()
      ^~~~