编译器生成的默认构造函数如何比自己编写的只初始化成员的构造函数更有效? [英]How can a compiler generated default constructor be more efficient than a self-written one that does nothing but initialize members?
`using namespace ...` 会增加编译时间还是会以某种方式影响性能? [英]Does `using namespace ...` increase compilation time or can it somehow affect performance?