inplace_vector is not trivially copyable

[lurtz]

Description

The folllowing code fails to compile:

#include <score/inplace_vector.hpp>
#include <type_traits>

static_assert(std::is_trivially_copyable_v<score::cpp::inplace_vector<int, 1>>);

The C++26 inplace_vector should be trivially copyable, if T is. At least that is the impression I get, when looking at some special member functions (constructor, destructor, assignment operator).

Thus if the score type aims to be a drop-in replacement it needs to be trivially copyable as well.

Analysis results

It looks like non trivial constructors, assignment operators and destructors are used.

Solution

No response

Error Occurrence Rate

Reproducible

How to reproduce

No response

Supporting Information

No response

Classification

Minor

First Affected Release

not released (main)

Last Affected Release

not released (main)

Expected Fixed Release

before release (main)

Category

• Safety Relevant
• Security Relevant

[4og]

Thanks for raising this, we are aware of this limitation. We previously had a trivially copyable implementation but had to revert it due to a significant performance impact. A trivial copy always copies the full MaxSize elements, whereas the current implementation only copies the actual size() elements.

[NEOatNHNG]

@4og OK but the whole point of futurecpp is to backport std features which are available in a later version right? And I would guess that if you used the same code also with C++26 stdlib it would also be slow, right? If so then for that code you need an optimized_inplace_vector which is then not having the trivial copy but is fast. These people can then use when needed. Otherwise we will have a bad surprise when we try to port the existing code to C++26.