What is a named object?

When talking about Return Value Optimisation (RVO), various texts mention exception cases related to the return of Named Objects. So开发者_JAVA技巧 in short:

• What are they?
• Is there a definition for this term in the current c++ standard?

Side note: I've tried to add the following tags: RVO and NRVO but due to lack of reputation points I wasn't able to take this post correctly

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A named object is just like it sounds:

  someclass foo() {
    someclass foo;
    foo.member = 42;
    return foo;
  }

As opposed to:

  someclass foo() {
    return someclass(42);
  }

The latter case is simple to optimize.