Why Doesn\'t C \'s Standard Library Offer a Non-Atomic Version of `std::shared_ptr`?

The Non-Atomic Equivalent of std::shared_ptr

Question:

Is there an alternative to std::shared_ptr that lacks its inherent atomicity? Moreover, why does the C Standard Library not include a non-atomic option?

Answer:

1. Availability of Non-Atomic Alternatives:

The C Standard Library does not offer a non-atomic variant of std::shared_ptr. However, third-party libraries may provide such implementations. Prior to the introduction of std::shared_ptr in C 11, many developers created their own reference-counted smart pointers, potentially offering non-atomic options.

2. Rationale for Atomic std::shared_ptr in C 11:

During the C 11 standardization process, the proposal to include a non-atomic version of std::shared_ptr was considered and ultimately rejected. The following arguments influenced this decision:

• Potential Misuse: Non-atomic smart pointers written in threaded code could introduce subtle and difficult-to-debug errors.
• Consistency and Interoperability: Having a single, consistent version of std::shared_ptr facilitates library interoperability and reduces confusion.
• Low Performance Cost: Atomic operations have a non-zero overhead, but it is mitigated by the use of move semantics, which avoid atomic operations during common operations like vector erasure and insertion.
• Custom Implementations: Developers can create their own non-atomic smart pointers if they desire.

Proposed Non-Atomic Version:

Despite the rejection in C 11, there may have been proposals for a non-atomic version of std::shared_ptr submitted to Boost or the standards committee. However, these proposals did not gain sufficient support for inclusion in the official standard.

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