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GSL: Guidelines Support Library

The Guidelines Support Library (GSL) contains functions and types that are suggested for use by the C++ Core Guidelines maintained by the Standard C++ Foundation. This repo contains Microsoft's implementation of GSL.

The entire implementation is provided inline in the headers under the gsl directory. The implementation generally assumes a platform that implements C++14 support.

While some types have been broken out into their own headers (e.g. gsl/span), it is simplest to just include gsl/gsl and gain access to the entire library.

NOTE: We encourage contributions that improve or refine any of the types in this library as well as ports to other platforms. Please see CONTRIBUTING.md for more information about contributing.

Project Code of Conduct

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.

Usage of Third Party Libraries

This project makes use of the Google Test testing library. Please see the ThirdPartyNotices.txt file for details regarding the licensing of Google Test.

Supported features

Microsoft GSL implements the following from the C++ Core Guidelines:

The following features do not exist in or have been removed from the C++ Core Guidelines:

This is based on CppCoreGuidelines semi-specification.

Quick Start

Supported Compilers / Toolsets

The GSL officially supports recent major versions of Visual Studio with both MSVC and LLVM, GCC, Clang, and XCode with Apple-Clang. For each of these major versions, the GSL officially supports C++14, C++17, C++20, and C++23 (when supported by the compiler). Below is a table showing the versions currently being tested (also see [.github/workflows/compilers.yml](the workflow).)

If you successfully port GSL to another platform, we would love to hear from you!

• Submit an issue specifying the platform and target.
• Consider contributing your changes by filing a pull request with any necessary changes.
• If at all possible, add a CI/CD step and add the button to the table below!

Target	CI/CD Status
iOS
Android

Note: These CI/CD steps are run with each pull request, however failures in them are non-blocking.

Building the tests

To build the tests, you will require the following:

• CMake, version 3.14 or later to be installed and in your PATH.

These steps assume the source code of this repository has been cloned into a directory named c:\GSL.

1. Create a directory to contain the build outputs for a particular architecture (we name it c:\GSL\build-x86 in this example).

    cd GSL
    md build-x86
    cd build-x86
   

2. Configure CMake to use the compiler of your choice (you can see a list by running cmake --help).

    cmake -G "Visual Studio 15 2017" c:\GSL
   

3. Build the test suite (in this case, in the Debug configuration, Release is another good choice).

    cmake --build . --config Debug
   

4. Run the test suite.

    ctest -C Debug
   

All tests should pass - indicating your platform is fully supported and you are ready to use the GSL types!

Building GSL - Using vcpkg

You can download and install GSL using the vcpkg dependency manager:

git clone https://github.com/Microsoft/vcpkg.git
cd vcpkg
./bootstrap-vcpkg.sh
./vcpkg integrate install
vcpkg install ms-gsl

The GSL port in vcpkg is kept up to date by Microsoft team members and community contributors. If the version is out of date, please create an issue or pull request on the vcpkg repository.

Using the libraries

As the types are entirely implemented inline in headers, there are no linking requirements.

You can copy the gsl directory into your source tree so it is available to your compiler, then include the appropriate headers in your program.

Alternatively set your compiler's include path flag to point to the GSL development folder (c:\GSL\include in the example above) or installation folder (after running the install). Eg.

MSVC++

/I c:\GSL\include

GCC/clang

-I$HOME/dev/GSL/include

Include the library using:

#include <gsl/gsl>

Usage in CMake

The library provides a Config file for CMake, once installed it can be found via find_package.

Which, when successful, will add library target called Microsoft.GSL::GSL which you can use via the usual target_link_libraries mechanism.

find_package(Microsoft.GSL CONFIG REQUIRED)

target_link_libraries(foobar PRIVATE Microsoft.GSL::GSL)

FetchContent

If you are using CMake version 3.11+ you can use the official FetchContent module. This allows you to easily incorporate GSL into your project.

# NOTE: This example uses CMake version 3.14 (FetchContent_MakeAvailable).
# Since it streamlines the FetchContent process
cmake_minimum_required(VERSION 3.14)

include(FetchContent)

FetchContent_Declare(GSL
    GIT_REPOSITORY "https://github.com/microsoft/GSL"
    GIT_TAG "v4.1.0"
    GIT_SHALLOW ON
)

FetchContent_MakeAvailable(GSL)

target_link_libraries(foobar PRIVATE Microsoft.GSL::GSL)

Debugging visualization support

For Visual Studio users, the file GSL.natvis in the root directory of the repository can be added to your project if you would like more helpful visualization of GSL types in the Visual Studio debugger than would be offered by default.

See Also

For information on Microsoft Gray Systems Lab (GSL) of applied data management and system research see https://aka.ms/gsl.