Advanced Custom Commands

Introduction

Custom commands can be tied to specific build events, such as pre-build or post-build steps. This allows you to automate tasks like:

• Running a code formatter before building.
• Copying files or running tests after building.
• Generating files dynamically based on build configurations.

Key Concepts

• PRE_BUILD, PRE_LINK, and POST_BUILD: These options tie custom commands to specific stages of the build process.
• Generator Expressions: Special CMake syntax (e.g., $<CONFIG:Debug>) that evaluates at build time.
• Combining Commands: Use multiple add_custom_command calls to create complex workflows.

Code Sample

1. We will start with the main.cpp file and the CMakeLists.txt file from Chapter 1.

#include <iostream>
int main() {
  std::cout << "Hello, World!" << std::endl;
  return 0;
}

2. In addition to the standard lines for compilations, add a few lines to CMakeLists.txt to run a command after the build completes.

cmake_minimum_required(VERSION 3.10)
project(HelloWorld)

add_executable(HelloWorld main.cpp)

# ----- Add this -----
# We want to run
# `cmake -E echo "Build succeeded!"`
# after the build
add_custom_command(
    TARGET HelloWorld POST_BUILD
    COMMAND ${CMAKE_COMMAND} -E echo "Build succeeded!"
    COMMENT "Running post-build step"
)

3. Run cmake and build, and observe the output

cmake ..
cmake --build .

4. Output:

...
Running post-build step
Build succeeded!

Quiz