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If any move, copy, or destructor is explicitly specified (declared, defined, =default, or =delete) by the user, no move is generated by default. If any move, copy, or destructor is explicitly specified (declared, defined, =default, or =delete) by the user, any undeclared copy operations are generated by default, but this is deprecated, so don‘t rely on that. For example:
class X1 { X1& operator=(const X1&) = delete; // Disallow copying };This implicitly also disallows moving of X1s. Copy initialization is allowed, but deprecated.
class X2 { X2& operator=(const X2&) = delete; }; This implicitly also disallows moving of X2s. Copy initialization is allowed, but deprecated. class X3 { X3& operator=(X3&&) = delete; // Disallow moving }; This implicitly also disallows copying of X3s. class X4 { ~X4() = delete; // Disallow destruction }; This implicitly also disallows moving of X4s. Copying is allowed, but deprecated.I strongly recommend that if you declare one of these five function, you explicitly declare all. For example:
template<class T> class Handle { T* p; public: Handle(T* pp) : p{pp} {} ~Handle() { delete p; } // user-defined destructor: no implicit copy or move Handle(Handle&& h) :p{h.p} { h.p=nullptr; } // transfer ownership Handle& operator=(Handle&& h) { delete p; p=h.p; h.p=nullptr; return *this; } // transfer ownership Handle(const Handle&) = delete; // no copy Handle& operator=(const Handle&) = delete; // ... }; See also
原文：http://www.cnblogs.com/likeatree/p/4193886.html