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In VBA, an assignment of variables of type Object is a shallow copy, an assignment for all other types (numeric types, String, user defined types, arrays) is a deep copy. So the keyword Set for an assignment signals a shallow copy and the (optional) keyword Let signals a deep copy. There is no built-in method for deep copies of Objects in VBA.
Because implicitly-generated constructors and assignment operators simply copy all class data members ("shallow copy"), [4] one should define explicit copy constructors and copy assignment operators for classes that encapsulate complex data structures or have external references such as pointers, if you need to copy the objects pointed to by ...
Array's destructor deletes the data array of the original, therefore, when it deleted copy's data, because they share the same pointer, it also deleted first's data. Line (2) now accesses invalid data and writes to it. This produces a segmentation fault. If we write our own copy constructor that performs a deep copy then this problem goes away.
Additionally, due to the lack of garbage collection in C++, programs will frequently copy an object whenever the ownership and lifetime of a single shared object would be unclear. For example, inserting an object into a standard library collection (such as a std::vector) typically involves making and inserting a copy into the collection.
Shallow copy, in contrast to deep copy; Single responsibility principle; Singleton pattern; Singly rooted hierarchy; Slicing; Specification class, a class implementing abstract class; Stack-based memory allocation; Static method; Static typing, in contrast to dynamic typing; Strong and weak typing; Subclass (also called child class or derived ...
In C++ computer programming, copy elision refers to a compiler optimization technique that eliminates unnecessary copying of objects.. The C++ language standard generally allows implementations to perform any optimization, provided the resulting program's observable behavior is the same as if, i.e. pretending, the program were executed exactly as mandated by the standard.
The libraries are aimed at a wide range of C++ users and application domains. They range from general-purpose libraries like the smart pointer library, to operating system abstractions like Boost FileSystem, to libraries primarily aimed at other library developers and advanced C++ users, like the template metaprogramming (MPL) and domain-specific language (DSL) creation (Proto).
A chronic performance problem with C++03 is the costly and unneeded deep copies that can happen implicitly when objects are passed by value. To illustrate the issue, consider that an std::vector<T> is, internally, a wrapper around a C-style array with a defined size.