__attribute__ ((unused))

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 '<variable_name>'
warning: unused function '<function_name>'

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.