嘘言ってました．-Wallつけると標準エラー出力にでます。warning
なので大丈夫とは思いますが．
yptest.c: In function `main':
yptest.c:11: warning: implicit declaration of function `exit'
yptest.c:16: warning: unknown conversion type character `;' in format
yptest.c:16: warning: unknown conversion type character `;' in format
yptest.c:16: warning: unknown conversion type character `;' in format
yptest.c:16: warning: unknown conversion type character `;' in format
yptest.c:16: warning: unknown conversion type character `;' in format
yptest.c:16: warning: unknown conversion type character `;' in format
yptest.c:16: warning: too many arguments for format