1.1.2. fejezet SmartPointer

Beküldte pzoli - 2017, szeptember 1 - 12:28du
  • What is a smart pointer?
    It's a type which can be used like a pointer, but provides the additional feature of automatic memory management: When the pointer is no longer in use, the memory it points to is deallocated (see also the more detailed definition on Wikipedia).
  • When should I use one?
    In code which involves tracking the ownership of a piece of memory, allocating or de-allocating; the smart pointer often saves you the need to do these things explicitly.
  • But which smart pointer should I use in which of those cases?
    • Use std::unique_ptr when you don't intend to hold multiple references to the same object. For example, use it for a pointer to memory which gets allocated on entering some scope and de-allocated on exiting the scope.
    • Use std::shared_ptr when you do want to refer to your object from multiple places - and do not want it to be de-allocated until all these references are themselves gone.
    • Use std::weak_ptr when you do want to refer to your object from multiple places - for those references for which it's ok to ignore and deallocate (so they'll just note the object is gone when you try to dereference).
    • Don't use the boost:: smart pointers or std::auto_ptr except in special cases which you can read up on if you must.
  • Hey, I didn't ask which one to use!
    Ah, but you really wanted to, admit it.
  • So when should I use regular pointers then?
    In code that is oblivious to memory ownership. This would typically be in functions which get a pointer from someplace else and do not allocate, de-allocate or store a copy of the pointer which outlasts their execution.