1.可以使用{}来达到方便的作用.
比如下面的代码,如果不用{}的话,会提示v1重复定义的问题
int sz = 100; std::cout << "using reserve: "; { std::vector<int, NAlloc<int>> v1; v1.reserve(sz); for(int n = 0; n < sz; ++n) v1.push_back(n); } std::cout << "not using reserve: "; { std::vector<int, NAlloc<int>> v1; for(int n = 0; n < sz; ++n) v1.push_back(n); }