#pragma GCC diagnostic [error|warning|ignored] "-W<警告选项>"
诊断-忽略:(关闭警告)
#pragma GCC diagnostic ignored "-Wunused"
#pragma GCC diagnostic ignored "-Wunused-parameter"
诊断-警告:(开启警告)
#pragma GCC diagnostic warning "-Wunused"
#pragma GCC diagnostic warning "-Wunused-parameter"
诊断-错误:(开启警告-升级为错误)
#pragma GCC diagnostic error "-Wunused"
#pragma GCC diagnostic error "-Wunused-parameter"
转载：https://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Pragmas.html