beman.elide: Implementation of Proposed std::elide

Implements: std::elide proposed in std::elide (P3288R3).

Status: Under development and not yet ready for production use.

License

beman.elide is licensed under the Apache License v2.0 with LLVM Exceptions.

Usage

std::elide is an object which:

• Wraps an invocable alongside the arguments thereto (by reference), and
• Implicitly converts to whatever that invocable yields

When combined with emplacement APIs this allows for the creation of instances of immovable types within storage managed by std::optional, std::list, et cetera.

Dependencies

Build Environment

This project requires at least the following to build:

• A C++ compiler that conforms to the C++20 standard or greater
• CMake 3.30 or later
• (Test Only) GoogleTest

You can disable building tests by setting CMake option BEMAN_ELIDE_BUILD_TESTS to OFF when configuring the project.

Supported Platforms

Compiler	Version	C++ Standards	Standard Library
GCC	16-13	C++26-C++20	libstdc++
GCC	12-11	C++23, C++20	libstdc++
Clang	22-19	C++26-C++20	libstdc++, libc++
Clang	18	C++26-C++20	libc++
Clang	18	C++23, C++20	libstdc++
Clang	17	C++26-C++20	libc++
Clang	17	C++20	libstdc++
AppleClang	latest	C++26-C++20	libc++
MSVC	latest	C++23	MSVC STL

Development

See the Contributing Guidelines.

Integrate beman.elide into your project

Build

You can build elide using a CMake workflow preset:

cmake --workflow --preset gcc-release

To list available workflow presets, you can invoke:

cmake --list-presets=workflow

For details on building beman.elide without using a CMake preset, refer to the Contributing Guidelines.

Installation

Vcpkg

The preferred way to install elide is via vcpkg. To do so, after installing vcpkg itself, you need to add support for the Beman project's vcpkg registry by configuring a vcpkg-configuration.json file (which elide provides).

Then, simply run vcpkg install beman-elide.

Manual

To install beman.elide globally after building with the gcc-release preset, you can run:

sudo cmake --install build/gcc-release

Alternatively, to install to a prefix, for example /opt/beman, you can run:

sudo cmake --install build/gcc-release --prefix /opt/beman

This will generate the following directory structure:

/opt/beman
├── include
│   └── beman
│       └── elide
│           ├── elide.hpp
│           └── ...
└── lib
    └── cmake
        └── beman.elide
            ├── beman.elide-config-version.cmake
            ├── beman.elide-config.cmake
            └── beman.elide-targets.cmake

CMake Configuration

If you installed beman.elide to a prefix, you can specify that prefix to your CMake project using CMAKE_PREFIX_PATH; for example, -DCMAKE_PREFIX_PATH=/opt/beman.

You need to bring in the beman.elide package to define the beman::elide CMake target:

find_package(beman.elide REQUIRED)

You will then need to add beman::elide to the link libraries of any libraries or executables that include beman.elide headers.

target_link_libraries(yourlib PUBLIC beman::elide)

Using beman.elide

To use beman.elide in your C++ project, include an appropriate beman.elide header from your source code.

#include <beman/elide/elide.hpp>

Note

beman.elide headers are to be included with the beman/elide/ prefix. Altering include search paths to spell the include target another way (e.g. #include <elide.hpp>) is unsupported.