Possible Variations for libxml2 include directory

Creating a Makefile is challenging:

• Must list all prerequisite include files (i.e., .h and .hpp files)
• Straightforward for an in-source build, more difficult for an out-of-source build
• Prefer an out-of-source build
• Make is Turing Complete, but conditional (e.g., if-statements) and repetition (e.g., for-statements) statements have an unfamiliar syntax
• Does not easily handle multiple platforms or multiple build configurations
• Limited internal and external libraries and additional support software

CMake

• CMake is a build-file generator and can generate build files for many platforms and environments
• cmake --help shows a list of Generators
• Related tools: ctest, cpack
• Has both command-line and GUI tools
• Under constant improvement
• Works well on Linux, macOS, and Windows MSVC

Using CMake

Build languages are declarative

• As opposed to imperative
• make
• nmake
• cmake
• Ant

Example: Using C++20

• Abstraction levels get higher over time
• Note that the literal flags, e.g., -std=c++20 are gcc/clang only, while MSVC takes /std:c++20
• More variation, history, and discussion (for C++17, but applies to any version) at How to enable C++17 in CMake
• CMake documentation: CMAKE_CXX_STANDARD and cmake-compile-features

There is always more to learn

• The cmake-provided target, install, has a variation, install/strip
• make install
• make install/strip
• Another Example: Download and install external source with FetchContent vs file(DOWNLOAD ...) vs ExternalProject vs find_package

Multiple structural design decisions to make

• srcML build file structure
• Full View
• Build file structure follows the source file tree structure
• Alternative: A single large CMakeLists.txt that knows the tree structure of the source (and prevents any change to that structure)

Types of CMake Files

• Full View
• CMakeLists.txt - The default name, found in the top directory and often in subdirectories
• CMakePresets.json JSON file with presets to use with the CMake option --preset. Much of the platform-specific build configuration has been moved from the CMakeLists.txt to these files, including the ones in the directory presets.
• CMakeUserPresets.json A JSON file with personal presets to use with the CMake option --preset. It is not committed to the repository and is developer-specific.
• toolchain-gcc.cmake CMake commands for a specific platform
• macos-libarchive.cmake Separates out specific processing from CMakeLists.txt
• srcMLConfig.cmake.in - Input for generating files for other CMake projects to be able to use find_package(srcML) (as with find_package(LibXml2 REQUIRED))
• CTestConfig.cmake - CDash configuration
• wix-cpack.cmake CPack configuration for a Windows WiX installer (generates an MSI installer). Custom naming convention so that installers can be loaded automatically.
• vcpkg.json A JSON file with a list of dependencies for vcpkg builds. vcpkg primarily aims to allow Windows developers to easily use open-source libraries in their applications. It integrates easily into CMake builds.

Build File Comparison: srcML

Summation

• Always use a build tool to build programs. Do not use direct entry of compiler commands unless it is part of a class where you are learning the commands. Build your knowledge into the build file instead of having to remember.
• Things don't always work the same on all platforms, so you have to experiment
• While CMake and other tools may be difficult, the main problem is that building code into an executable or installer has many difficult situations
• In some ways, build files are static and dynamic. They tend to be created and left alone for a long time, but then change drastically when the project structure or platforms change.