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Windows Implementation Libraries (WIL)

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The Windows Implementation Libraries (WIL) is a header-only C++ library created to make life easier for developers on Windows through readable type-safe C++ interfaces for common Windows coding patterns.

Some things that WIL includes to whet your appetite:

  • include/wil/resource.h (documentation): Smart pointers and auto-releasing resource wrappers to let you manage Windows API HANDLEs, HWNDs, and other resources and resource handles with RAII semantics.
  • include/wil/win32_helpers.h: Wrappers for API functions that save you the work of manually specifying buffer sizes, calling a function twice to get the needed buffer size and then allocate and pass the right-size buffer, casting or converting between types, and so on.
  • include/wil/registry.h: Registry watchers that can call a lambda function or callback you provide whenever a certain tree within the Windows registry changes.
  • include/wil/result.h (documentation): Preprocessor macros to help you check for errors from Windows API functions, in many of the myriad ways those errors are reported, and surface them as error codes or C++ exceptions in your code.

WIL can be used by C++ code that uses C++ exceptions as well as code that uses returned error codes to report errors. All of WIL can be used from user-space Windows code, and some (such as the RAII resource wrappers) can even be used in kernel mode.


This project is documented in its GitHub wiki. Feel free to contribute to it!

Consuming WIL

WIL follows the "live at head" philosophy, so you should feel free to consume WIL directly from the GitHub repo however you please: as a GIT submodule, symbolic link, download and copy files, etc. and update to the latest version at your own cadence. Alternatively, WIL is available using a few package managers, mentioned below. These packages will be updated periodically, likely to average around once or twice per month.

Consuming WIL via NuGet

WIL is available on under the name Microsoft.Windows.ImplementationLibrary. This package includes the header files under the include directory as well as a .targets file.

Consuming WIL via vcpkg

WIL is also available using vcpkg under the name wil. Instructions for installing packages can be found in the vcpkg GitHub docs. In general, once vcpkg is set up on the system, you can run:

C:\vcpkg> vcpkg install wil:x86-windows
C:\vcpkg> vcpkg install wil:x64-windows

Note that even though WIL is a header-only library, you still need to install the package for all architectures/platforms you wish to use it with. Otherwise, WIL won't be added to the include path for the missing architectures/platforms. Execute vcpkg help triplet for a list of available options.


To get started testing WIL, first make sure that you have a recent version of Visual Studio and the most recent Windows SDK installed. If you are doing any non-trivial work, also be sure to have a recent version of Clang installed. Once everything is installed, open a VS native command window (e.g. "x64 Native Tools Command Prompt for VS 2019"). If you are familiar with CMake you can get started building normally. Otherwise, or if you prefer to skip all of the boilerplate, you can use one of the scripts in the scripts directory:

C:\wil> scripts\init.cmd -c clang -g ninja -b debug

You can execute init.cmd --help for a summary of available options. The scripts use a common directory pattern of build/$(compiler)$(arch)$(type) for the build output root. E.g. build/clang64debug when using Clang as the compiler, x64 as the architecture, and Debug as the build type. It is this directory where you will want to build from. For example, if you initialized using the command above, you can build the tests like so:

C:\wil\build\clang64debug> ninja

Or, if you want to only build a single test (e.g. for improved compile times):

C:\wil\build\clang64debug> ninja witest.noexcept

If you initialized using MSBuild as the generator, there will be a .sln file in the root of the build directory. You can either open the solution in Visual Studio or invoke MSBuild directly to build.

The output is a number of test executables. If you used the initialization script(s) mentioned above, or if you followed the same directory naming convention of those scripts, you can use the runtests.cmd script, which will execute any test executables that have been built, erroring out - and preserving the exit code - if any test fails. Note that MSBuild will modify the output directory names, so this script is only compatible with using Ninja as the generator. If you are at the tail end of of a change, you can execute the following to get a wide range of coverage:

C:\wil> scripts\init_all.cmd
C:\wil> scripts\build_all.cmd
C:\wil> scripts\runtests.cmd

Note that this will only test for the architecture that corresponds to the command window you opened. You will want to repeat this process for the other architecture (e.g. by using the "x86 Native Tools Command Prompt for VS 2019")


This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit

When you submit a pull request, a CLA-bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., label, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.

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

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