What is copy elision and when does it occur?

Copy elision is an optimization technique used by C++ compilers to eliminate unnecessary copying of objects. It aims to enhance performance by directly constructing objects in their final location rather than making temporary copies. This optimization can happen under certain conditions, particularly during the return of local objects from functions and when passing objects by value.

Copy elision typically occurs when:

  • Returning a temporary object from a function.
  • Passing objects by value to constructors or other functions.
  • Using initializer lists in constructors.

Example:

class Example { public: Example() { std::cout << "Constructor called\n"; } Example(const Example&) { std::cout << "Copy constructor called\n"; } }; Example createExample() { return Example(); // Copy elision may occur here } int main() { Example ex = createExample(); // No copy constructor if copy elision occurs return 0; }

copy elision C++ optimization object copying performance enhancement temporary objects

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