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.
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
Usage of Third Party Libraries
Microsoft GSL implements the following from the C++ Core Guidelines:
|owner||an alias for a raw pointer|
|not_null||restricts a pointer / smart pointer to hold non-null values|
|span||a view over a contiguous sequence of memory. Based on the standardized version of
|span_p||☐||spans a range starting from a pointer to the first place for which the predicate is true|
|basic_zstring||A pointer to a C-string (zero-terminated array) with a templated char type|
|zstring||An alias to
|czstring||An alias to
|wzstring||An alias to
|cwzstring||An alias to
|u16zstring||An alias to
|cu16zstring||An alias to
|u32zstring||An alias to
|cu32zstring||An alias to
|unique_ptr||an alias to
|shared_ptr||an alias to
|stack_array||☐||a stack-allocated array|
|dyn_array||☐||a heap-allocated array|
|Expects||a precondition assertion; on failure it terminates|
|Ensures||a postcondition assertion; on failure it terminates|
|move_owner||☐||a helper function that moves one
|byte||either an alias to std::byte or a byte type|
|final_action||a RAII style class that invokes a functor on its destruction|
|finally||a helper function instantiating
|GSL_SUPPRESS||a macro that takes an argument and turns it into
|[[implicit]]||☐||a "marker" to put on single-argument constructors to explicitly make them non-explicit|
|index||a type to use for all container and array indexing (currently an alias for std::ptrdiff_t)|
|joining_thread||☐||a RAII style version of
|narrow||a checked version of narrow_cast; it can throw
|narrow_cast||a narrowing cast for values and a synonym for static_cast|
|narrowing_error||a custom exception type thrown by
The following features do not exist in or have been removed from the C++ Core Guidelines:
|strict_not_null||A stricter version of
|multi_span||☐||Deprecated. Multi-dimensional span.|
|strided_span||☐||Deprecated. Support for this type has been discontinued.|
|string_span||☐||Deprecated. An alias to
|cstring_span||☐||Deprecated. An alias to
|wstring_span||☐||Deprecated. An alias to
|cwstring_span||☐||Deprecated. An alias to
|u16string_span||☐||Deprecated. An alias to
|cu16string_span||☐||Deprecated. An alias to
|u32string_span||☐||Deprecated. An alias to
|cu32string_span||☐||Deprecated. An alias to
This is based on CppCoreGuidelines semi-specification.
Supported Compilers / Toolsets
The GSL officially supports the latest and previous major versions of VS with MSVC & LLVM, GCC, Clang, and XCode with Apple-Clang. Within these two major versions, we try to target the latest minor updates / revisions (although this may be affected by delays between a toolchain's release and when it becomes widely available for use). Below is a table showing the versions currently being tested.
|Compiler||Toolset Versions Currently Tested|
|XCode||13.2.1 & 12.5.1|
|GCC||111 & 102|
|Clang||122 & 112|
|Visual Studio with MSVC||VS20223 & VS20194|
|Visual Studio with LLVM||VS20223 & VS20194|
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!
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 3.8 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
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
Configure CMake to use the compiler of your choice (you can see a list by running
cmake -G "Visual Studio 15 2017" c:\GSL
Build the test suite (in this case, in the Debug configuration, Release is another good choice).
cmake --build . --config Debug
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.
Include the library using:
Usage in CMake
The library provides a Config file for CMake, once installed it can be found via
Which, when successful, will add library target called
Microsoft.GSL::GSL which you can use via the usual
find_package(Microsoft.GSL CONFIG REQUIRED) target_link_libraries(foobar PRIVATE Microsoft.GSL::GSL)
If you are using CMake version 3.11+ you can use the offical 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 "v4.0.0" 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.
If you are using CMake this will be done automatically for you. See 'GSL_VS_ADD_NATIVE_VISUALIZERS'