Why Doesn't `std::shared_ptr` Have a Specialization for Array Types?

Specialization of std::shared_ptr: An Enigma

The C Standard Library includes a specialized template for std::unique_ptr that appropriately invokes delete[] in its destructor. However, a similar specialization is absent for std::shared_ptr, necessitating the use of a custom deleter to correctly deallocate arrays.

Reason for the Lack of Specialization

Initially, the omission of std::shared_ptr specialization appeared to be mere oversight. However, it emerged that there was no consensus within the Library Working Group (LWG) on the addition of such a feature. The primary concern stemmed from the suggestion to include arithmetic operations on shared_ptr, a feature that could have been discarded.

Ultimately, the absence of a proposal for std::shared_ptr specialization proved decisive in its omission from the C Standard. While discussions have recently resumed among LWG members, no formal proposal has yet materialized.

Current Status

Despite the lack of a specialized template, C 17 introduced partial array support for shared_ptr, as specified in the shared_ptr::shared_ptr() method's third case. This update allows for the creation and destruction of arrays using shared_ptr, albeit without the convenience of a dedicated specialization.

Future Prospects

The draft TS (Technical Specification) N4077 outlined a potential path towards array support in shared_ptr, and this feature was eventually incorporated into C 17. The continued development of C may bring further enhancements to this area, offering additional flexibility and expressiveness for array management using shared pointers.

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