今天编译 ｔｃｐｄｕｍｐ 看到这个选项。。谷歌了下，原来是去除 编译器对未引用的函数的警告的，
Problem: I received the following warning:
warning: unused variable ''warning: unused function ' '
Solution: If variable <variable_name> or function <function_name> is not used, it can be removed. If it is only used sometimes, you can use __attribute__((unused)). This attribute suppresses these warnings. For example:
int __attribute__ ((unused)) myfunction(int parm1, long parm2) { … }long __attribute__ ((unused)) myvariable; If there are a large number of unused variables or functions, which can happen with ported code, you can add the -Wno-unused compiler option to your makefile. This option suppresses all unused warnings.