简单介绍 

__func__	当前调试的函数的名字
__FILE__	存放文件名的字符串的字面值
__LINE__	存放当前行号的整型字面值
__TIME__	存放文件编译时间的字符串的字面值
__DATE__	存放文件编译日期的字符串的字面值

例子

    if(word.size() < threshold){cerr << "Error: " << __FILE__ << " : in function " << __func__ << "at line " <<__LINE__ << " Compiled on " << __DATE__ << " at " << __TIME__ << " Word read was \"" << word<< "\":Length too short" << endl;}