$ gcc t.c $Compile with warnings:
$ gcc -O4 -Wall -Werror t.c cc1: warnings being treated as errors t.c:9: warning: return-type defaults to `int' t.c:9: warning: first argument of `main' should be `int' t.c:9: warning: `main' takes only zero or two arguments t.c: In function `main': t.c:13: warning: implicit declaration of function `printf' t.c:13: warning: double format, different type arg (arg 2) t.c:10: warning: unused variable `c' t.c:14: warning: control reaches end of non-void function t.c:10: warning: `b' might be used uninitialized in this function