How to Set Compiler Flags in Cross-Platform CMake Projects Using Generator Expressions?

Modern Way to Set Compiler Flags in Cross-Platform CMake Projects

Elegant Solution Using CMake Generator Expressions

While your approach is valid, modern CMake provides a more concise and robust solution using CMake's generator expressions:

cmake_minimum_required(VERSION 3.8)

project(HelloWorld)

string(
    APPEND _opts
    "$<IF:$<CXX_COMPILER_ID:MSVC>,"
        "/W4;$<$<CONFIG:RELEASE>:/O2>,"
        "-Wall;-Wextra;-Werror;"
            "$<$<CONFIG:RELEASE>:-O3>"
            "$<$<CXX_COMPILER_ID:Clang>:-stdlib=libc++>"
    ">"
)

add_compile_options("${_opts}")

Compared to your original approach, this method leverages:

• Generator expressions to conditionally define compiler options based on compiler and configuration.
• The string(APPEND ...) command to accumulate the options in a list.
• The add_compile_options() function to set the options for all targets.

Deprecation of Manual Flag Setting

As you've noticed, it's generally discouraged to manually set CMAKE_CXX_FLAGS and similar variables. Instead, prefer using the add_compile_options() function to append options without modifying the global flags.

Multi-Target Project Setup

To create multiple targets with different options in the same directory, you can use CMake's target properties:

add_executable(HelloWorld_Debug_Clang HelloWorld.cpp)
target_compile_options(HelloWorld_Debug_Clang PRIVATE "-std=c++1z;-W4")
target_link_libraries(HelloWorld_Debug_Clang PRIVATE libc++)

add_executable(HelloWorld_Release_Gcc HelloWorld.cpp)
target_compile_options(HelloWorld_Release_Gcc PRIVATE "-std=c++1z;-W3")
target_link_libraries(HelloWorld_Release_Gcc PRIVATE libstdc++)

This approach allows you to specify different compiler options for each target, while keeping a single project file.

Modern Best Practices

• Use CMake generator expressions for conditional flag setting.
• Favor add_compile_options() over manually setting CMAKE_CXX_FLAGS.
• Create multiple targets with distinct compiler options for cross-platform compatibility.
• Utilize a build wrapper script to generate multiple configurations from a single CMake file.

The above is the detailed content of How to Set Compiler Flags in Cross-Platform CMake Projects Using Generator Expressions?. For more information, please follow other related articles on the PHP Chinese website!