Why Did Early C 11 Drafts Omit Implicit Move Semantics?

Lack of Automatic Move Semantics in Early C 11 Drafts

As a programmer working primarily with POD-types and STL containers, writing explicit assignment operators and copy constructors is largely unnecessary due to their default implementation. However, the absence of automatic move semantics in early drafts of the C 11 standard raised concerns about ease of use and safety.

The implicit generation of move constructors and assignment operators has been the subject of much debate and revisions in the C Standard. In early drafts, these semantics were not automatically provided, posing a challenge for programmers trying to leverage move capabilities without additional coding effort.

The current specification (N3225) provides more stringent conditions for implicit move generation. To have an implicitly declared move constructor, a class X must meet several criteria, including:

• No user-declared copy constructor, copy assignment operator, move assignment operator, or destructor
• Satisfy specific conditions that prevent the move constructor from being implicitly defined as deleted

Similar language applies to implicit move assignment operators. These restrictions were introduced to address concerns about potential conflicts between implicit and user-defined semantics, as well as misuse of move semantics.

The lack of implicit move semantics in early C 11 drafts required programmers to manually implement these functions if they wished to take advantage of move capabilities. However, subsequent revisions to the standard have addressed this issue, making implicit move generation more widely available and simplifying the use of move semantics for object ownership management.

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