This project demos the material covered in the CppCon 2019 talk "Are We Macro-free Yet?" The project includes:

• two ways of implementing a function with platform-dependent APIs, and
• how to implement a sha256 class with multiple, conditionally available backends, coexist at runtime

without any use of #if, #ifdef, or #define.

This demo maintains build tools and third-party libraries with Anaconda. Please go to here, download and install the latest version on your platform.

After the conda command is available in your shell, change the working directory to the project root directory and execute:

conda env create -f environment.yml
conda activate macrofree-demo

The rest of the article assumes that you are in the "macrofree-demo" Conda environment.

The build requires gcc>=7.0 or clang>=4.0.

Build and run the tests:

cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=Debug .
ninja -C build
./build/tests/run

The Conda environment has OpenSSL under Linux. You can verify that the test suite is testing a single sha256_openssl implementation with the following command:

./build/tests/run -ltc

"-ltc" (list test cases) is a command-line option provided by doctest.

The build requires Visual Studio 2019.

In "Native Tools Command Prompt":

cmake -B build .
msbuild build\macrofree_demo.sln
build\tests\Debug\run.exe

Alternatively, you can specify -DCMAKE_CXX_COMPILER=cl.exe in CMake command-line and keep using Ninja.

Usually, only CNG (Cryptography API: Next Generation) implementation is available at this point. If you install OpenSSL with

conda install -c conda-forge openssl

reconfigure and rebuild

cmake build
msbuild build\macrofree_demo.sln

You will find that the same test case runs against both sha256_cng and sha256_openssl implementations.