SG14 VS function2

There was a proposal for an `inplace_function` that uses static memory. There was a full implementation made. It's not the best solution for this problem though

There was a proposal for such functionality but I don't know what happened to it. It seems abandoned. There is full implementation in the same repo.

The only faster alternative that doesn't lose much flexibility would be to roll your own custom version of std::function that has a medium sized std::aligned_storage_t (or just an std::max_align_t aligned array of std::byte or unsigned char) buffer instead of using a dynamic allocation to hold its functor data. (Or use an implementation of the proposed inplace_function such as https://github.com/WG21-SG14/SG14/blob/master/SG14/inplace_function.h )

There's a repository for SG14 on GitHub here: https://github.com/WG21-SG14/SG14

The SG14 inplace_function takes a similar approach to what you suggest. The only minor downside there is that the way it's implemented makes the type unsafe to use across dll boundaries, due to possible mismatching addresses of the default binding. I guess that's not really a consideration for the C++ standard though, and anyway since std::function can allocate then it's inherently unsafe in that scenario anyway.

He was trying to standardize his implementation, but I (sadly) don't know what's happened to it since then: https://github.com/WG21-SG14/SG14/blob/master/Docs/Proposals/Fixed_Point_Library_Proposal.md

Fixed size function wrappers are not only limited and also a waste of space. Use a configurable function wrapper like fu2 with a stack allocator and set small object optimizer capacity to 0.

std::function wasn't cutting it for me, but I ended up going with fu2::function. It comes with a lot of features (almost too many), but the header size and compile times are comparable to , and it fit my needs pretty well.

Thank you, function2 is also used heavily in Idle as a type-erasure backend for continuable that is the primary asynchronous task abstraction.

You can write your own std::function, too, nor is it the only STL type that can take a capturing lambda (std::packaged_task for example).

A capturing lambda is just a class with an operator(). It's complicated to do what std::function does, but fully possible.

In fact, custom std::function replacements have better lambda support than std::function itself. Such as unique_function in https://github.com/Naios/function2 which can handle non-copyable lambdas.