----- Mensaje original ----- De: "Aaron W. LaFramboise" <aaronrabiddog51@aaronwl.com> Fecha: Domingo, Junio 3, 2007 5:12 pm Asunto: [boost] Uninitialized storage container to delay construction? Para: boost@lists.boost.org

Does Boost have some sort of uninitialized storage container? Presently, I use this pattern if I want to delay construction of a sub-object.

class my_class { public: my_class() { // ... subobject = auto_ptr<type>(new type(params)); } private: auto_ptr<type> subobject; };

But I'd like something similar that didn't use the heap, but instead allocated the storage for the sub-object within the class object itself. Perhaps it would look like this.

class my_class2 { public: my_class2() { // ... subobject.construct(params); } private: uninitialized_container<type> subobject; };

A TR1 array<T, sizeof(T)> almost works, except for these points: (1) It doesn't provide proper alignment guarantees. (2) It doesn't call the destructor when it is destroyed.

So, does Boost have any such thing?

I think you want to use aligned_storage and alignment_of from Boost.TypeTraits: aligned_storage< sizeof(type),alignment_of<type>::value>::type subobject; which provides the alignment guarantees. (2) OTOH is not taken care of by this construct, so it' still your responsibility to clean up subobject (by doing something like ((type*)&subobject)->~type()) when appropriate. HTH, Joaquín M López Muñoz Telefónica, Investigación y Desarrollo