Crafting Dynamic CMakeLists: Leveraging string() for Flexible Workflows

• Generation
  CMake provides functionalities to generate strings like random numbers (RANDOM) or timestamps (TIMESTAMP).
• Comparison
  The COMPARE function allows you to compare strings and store the result (equal, greater than, etc.) in a boolean variable.
• Search and Replace
  You can perform regular expression based search and replace operations with REGEX REPLACE.
• Manipulation
  There are functions to convert strings to uppercase/lowercase (TOUPPER, TOLOWER), strip whitespace (STRIP), and extract substrings (SUBSTRING).
• Concatenation
  You can use string(CONCAT) to merge multiple strings into a single string variable.

These manipulations can be helpful when defining variables based on conditions, creating file paths, or working with user input during the CMake configuration process.

Here are some examples of how string() can be used in CMakeLists.txt:

• Concatenating a path
  

set(PROJECT_NAME "MyProject")
set(SOURCE_DIR "${PROJECT_SOURCE_DIR}/src")
string(CONCAT PROJECT_BINARY_DIR "${CMAKE_BINARY_DIR}/${PROJECT_NAME}")

• Extracting filename from a path
  

set(FILE_PATH "/path/to/myfile.txt")
string(SUBSTRING FILE_PATH FILENAME -1 EXT)

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Concatenating Paths

This example creates a variable OUTPUT_FILE by combining the project's build directory and the filename "output.txt":

set(CMAKE_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}")  # Assuming you want current build directory
set(OUTPUT_FILENAME "output.txt")
string(CONCAT OUTPUT_FILE "${CMAKE_BINARY_DIR}/${OUTPUT_FILENAME}")

Conditional Include Directories

This example checks if a specific library is found and adds its include directory to the project:

find_package(SomeLibrary REQUIRED)  # Replace with actual library name
if(SOME_LIBRARY_FOUND)
  string(APPEND INCLUDE_DIRECTORIES "${SOME_LIBRARY_INCLUDE_DIRS}")
endif()

Extracting File Extension

This code extracts the file extension (".txt", ".cpp", etc.) from a filename:

set(FILE_PATH "data.csv")
string(SUBSTRING FILE_PATH FILE_EXTENSION -1)  # Extract from the end
message("File extension: ${FILE_EXTENSION}")

String Replacement with Regular Expression

This example replaces all occurrences of "v1" with "v2" in a version string:

set(VERSION_STRING "This is version v1.0")
string(REGEX REPLACE "v1" "v2" VERSION_STRING "${VERSION_STRING}")
message("Updated version: ${VERSION_STRING}")

Converting String to Uppercase

This code converts a user-provided string to uppercase:

message("Enter a string (in lowercase): ")
set(USER_INPUT STDIN)
string(TOUPPER USER_INPUT "${USER_INPUT}")
message("String in uppercase: ${USER_INPUT}")

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Using External Scripts

• You can write external scripts (e.g., Python, Bash) to perform complex string manipulations and call them within your CMakeLists.txt using execute_process(). However, this approach adds complexity and can make your project less portable.

Custom Functions

• You can define custom CMake functions that encapsulate specific string manipulation logic. This can improve code organization, but it requires writing and maintaining the functions yourself.

Looping and String Operations

• For very basic manipulations, you might achieve similar results by looping through characters in a string and manipulating them individually. However, this approach is generally less readable and more error-prone compared to using string().

• If integrating with external tools that require specific string manipulation techniques, you might need to resort to their specific methods.
• If you need very complex string manipulation logic beyond what string() offers, external scripts or custom functions could be an option. However, for most cases, string() provides sufficient functionality.

Important Note

While alternatives exist, string() is generally the preferred approach due to its:

• Maintainability
  CMake documentation and community support readily address its usage.
• Portability
  It's a built-in CMake function, ensuring consistent behavior across platforms.
• Readability
  The syntax is clear and concise for common string manipulations.