Printing Variables in CMakeLists.txt: A Simple Guide
CMake is a powerful tool for managing and building software projects. Often, you need to debug your CMake configuration or simply print the values of variables for informational purposes. This article will guide you through the process of printing variable values within your CMakeLists.txt file.
The Problem: Displaying Variable Values in CMake
Let's say you have a variable in your CMakeLists.txt file called PROJECT_NAME and you want to display its value during the build process. You might be thinking, "How do I print the contents of this variable?".
Solution: Using message()
CMake provides a built-in command called message() that's perfect for printing information during the build process. Here's how you can use it to print the value of your PROJECT_NAME variable:
# Set the variable
set(PROJECT_NAME "My Awesome Project")
# Print the variable value
message("Project Name: ${PROJECT_NAME}")
In this example, message() takes a string as an argument. We use string interpolation with ${PROJECT_NAME} to insert the value of the variable directly into the message.
Understanding the Output
When you run CMake, the message() command will print its content to the console output. In this case, you'd see the following output:
Project Name: My Awesome Project
Additional Considerations
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Message Levels:
message()can be used to print different types of messages. You can specify a severity level usingmessage(<LEVEL> "<message>"):FATAL_ERROR: Terminates the build process.SEND_ERROR: Prints an error message and continues the build.WARNING: Prints a warning message and continues the build.STATUS: Prints a status message (default behavior).NOTICE: Prints a notice message.
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Conditional Printing: You can use
if()statements to print messages only under specific conditions:if(CMAKE_BUILD_TYPE STREQUAL "Debug") message(STATUS "Building in Debug mode.") endif()
Conclusion
Printing variable values in CMakeLists.txt using the message() command is a simple but essential technique for debugging and understanding your CMake configuration. By leveraging this command effectively, you can ensure your build process runs smoothly and debug any potential issues with ease.
