[scope] Proposing Boost.Scope

From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2023-03-22 01:41:27

Hi,

I'm proposing a Boost.Scope library for review and potential inclusion
into Boost.

Boost.Scope is a small library implementing utilities defined in
<experimental/scope> from C++ Extensions for Library Fundamentals v3
with a few extensions. Namely, the library contains:

* A number of scope guards for various use cases.
* A unique resource wrapper that automatically frees the resource on
destruction.
* Utilities for wrapping POSIX-like file descriptors in the unique
resource wrapper.

Compared to <experimental/scope>, some notable extensions are:

* A new scope_final scope guard, which is a more lightweight alternative
to scope_exit. It is accompanied with the BOOST_SCOPE_FINAL macro that
allows to simplify scope guard declaration syntax.
* Scope guards can be activated/deactivated multiple times.
* Scope guards can be created inactive initially.
* Scope guard factory functions, for compatibility with C++11.
* Support for optional resource traits in unique_resource wrapper, which
improves usage with resources having unallocated values.
* unique_resource supports swapping.
* unique_resource supports dereferencing for any resource types that
support dereferencing, not only pointers.
* More flexible constructors for unique_resource.

The library requires C++11 at the minimum and will significantly benefit
from C++17.

Source:

https://github.com/Lastique/scope

Docs:

https://lastique.github.io/scope/libs/scope/doc/html/index.html

Current state: Feature complete, tested in the CI.

I'm asking for a review manager and endorsements.

I'm also looking forward for any pre-review comments. In particular, I'm
interested in community opinion on the following:

* Is there interest in this library at all?
* Should it be merged with Boost.ScopeExit, which is currently
unmaintained? More on this below.
* Should some/all of the library components be lifted to namespace
boost? Such is the practice with most vocabulary types in Boost, e.g.
boost::atomic, boost::shared_ptr, boost::any, boost::string_view, etc.
Currently, the library defines its names in namespace boost::scope.
* Comments on the resource traits feature are especially welcome.

Re. Boost.ScopeExit. There is significant functionality overlap with it
in the scope guards department. The docs contain comparison with it. I
believe there is room for both libraries because Boost.ScopeExit
supports C++03 and Boost.Scope provides better syntax and more features,
and both can be useful in their own regards, although I expect
Boost.Scope to be more appealing in newer code bases. However, if the
community decides there's too much overlap, I'm not opposed to merging
the two libraries, although Boost.ScopeExit currently depends on
Boost.Function, Boost.Preprocessor and Boost.TypeOf, which are
unnecessary for Boost.Scope.

Thank you.