/in/foo.c: In function 'main':
/in/foo.c:20:3: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
   if(s(a)==0);
   ^~
/in/foo.c:21:4: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'if'
    i=0;
    ^
/in/foo.c:24:4: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
    if(i=0)
    ^~
/in/foo.c: In function 's':
/in/foo.c:13:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^