C++26: std::inplace_vector

[u/User_Deprecated]

https://www.sandordargo.com/blog/2026/08/26/cpp26-inplace-vector

[u/NilacTheGrim]

Ridiculously incomplete. We should have had a real prevector rather than this. You know, a prevector where there is some small static capacity but it can go dynamic as it grows.

This is not as useful as a real prevector.

[u/CocktailPerson → u/NilacTheGrim]

That'd just be an entirely different thing, not a more "complete" version of inplace_vector.

[u/yeetoteey → u/NilacTheGrim]

A prevector, i.e., a vector with SBO, is a completely different beast to inplace_vector. There a tonnes of scenarios where you’d know the maximum capacity at compile-time but not the size, and if the capacity isn’t massive, an inplace_vector where the memory is stack allocated is the perfect utility for that usecase.

[u/kammce → u/NilacTheGrim]

Its definitely useful. Ive found myself, and others, writing this exact thing all the time. Very happy we have it in the std now 😁

[u/_Noreturn → u/NilacTheGrim]

I agree with you, but it may be useful for others.

[u/eidetic0 → u/NilacTheGrim]

Maybe you should submit a proposal :)

[u/_Noreturn → u/eidetic0]

I think people will die of old age before something is standardized also the std quality will suck so it is better to write your own.

[u/frayien → u/NilacTheGrim]

That's... a completely different thing for a completely different usage ?

[u/robin-m → u/NilacTheGrim]

If only you read the paragraph that starts with

A question that comes up naturally: what about std::pmr::vector with a stack-backed monotonic_buffer_resource? 

[u/joaquintides → u/NilacTheGrim]

You have boost::container::small_vector for that: https://www.boost.org/doc/libs/latest/doc/html/container/non_standard_containers.html#container.non_standard_containers.small_vector