ladnir / ProjectTemplate

A template project

Project template

This is an example project for libOTe applications. There are the following cpp components

• projTemp library: this is the main library where the core code should go
• tests library: this is where all the tests should go
• frontend: this is an executable. Unit tests and the main application can be launched from here.

When using build.py, output files are written to out/build/<platform>. For example, on linux the executable is written to out/build/linux/frontend/frontend.

cmake

There is a cmake folder that contains most of the cmake code. This includes the ability to automaticly fetch dependancies. The structure is:

• Config.cmake.in: This is what cmake will "install" so that others can find your project. It gets converted into a file call <install-prefix>/lib/cmake/projTempConfig.cmake. When someone types find_package(projTemp), this file is what cmake looks for. It has a few tasks. First it must define the targets of this project, e.g. libprojTemp.a on linux which will be referenced as the target pt::projTemp in cmake. This file must also find all dependancies of the targets which it defines. We handle finding the dependancies in the next cmake file.

• findDependancies.cmake: This file is where we place all the logic for finding dependancies. This sample project depends on libOTe and sparsehash. See the file for details. In addition, there is some logic here that will automaticly download the dependancies. The actual code that downloads and build the dependancies is located in thirdparty/getXXX.cmake where XXX is the dependancy name.

Since when we install this project, the downstream project (via find_package(projTemp)) also need to find our dependancies, this file will be installed next to projTempConfig.cmake. So this file can be called in two contexts, one where is lives in <src-tree>/cmake and one where it lives at <install-prefix>/lib/cmake/.

• buildOptions.cmake: here we define any compile time options. In this project we have one PROJTEMP_ENABLE_X. This gets define in cmake and then propegated to the cpp files via the projTemp/config.g.in file. Note that and build options which downstream users of your library should have access to as a cmake variable should be added to Config.cmake.in. See that file for an example.

• install.cmake: here we define all the install steps for our library. Note that thirdparty/getXXX.cmake handles install any dependancies that we fetched.

• preamble.cmake: here we define various project wide setting.

• projTempConfig.cmake: having this file allows users of the library find and use our source tree when they call find_package(projTemp). This enables users of our library to not install our project and instead just use the source tree.

As mentioned, thirdparty/getXXX.cmake is used to automaticly download and build dependancies. There are a few things worth mentioning:

• first is that dependancies are not fetched by default when using cmake. You can explicitly ask to fetch a dependancy XXX with -DFETCH_XXX=ON. Alternatively, you can have the cmake only fetch the dependancy if its not already installed with -DFETCH_AUTO=ON. The latter is convinent but in some situations might find the wrong version so use with care.

• Dependancies are downloaded into the thirdparty/ directory and then installed to <src-tree>/out/install/<platform>/. This is where cmake will look for the dependancies. When the user calls cmake install, we also install the dependancies to their specified locations. This "user install" case is handled at the end of thirdparty/getXXX.cmake file.

build.py

For convenience, there is a helper script build.py. This allows for an easy way to build the library. For more options, call python3 build.py --help. Note: when using visual studio, there are some issues in that visual studio uses the Ninja generator while the build.py uses the visual studio generator. If you first call build.py, then open the project in visual studio there will be a configure error. However, the reverse order does work (open is visual studio and then call build.py).