How to Modernize Compiler Flag Settings in Cross-Platform CMake Projects?

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

Introduction

This article provides guidance on setting compiler flags in cross-platform CMake projects. It addresses concerns raised about the existing approach and explores improved methodologies.

Improved Syntax with Generator Expressions

The previous approach used set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ..."), which can be replaced with append(CMAKE_CXX_FLAGS "..."). Additionally, the "dirty generator expressions" can be utilized to introduce conditions and list options concisely:

<code class="cmake">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}")</code>

Backward-Compatible Approach with add_compile_options()

For backward compatibility, alternative syntax using add_compile_options() can be employed:

<code class="cmake">if(MSVC)
    add_compile_options("/W4" "$<$<CONFIG:RELEASE>:/O2>")
else()
    add_compile_options("-Wall" "-Wextra" "-Werror" "$<$<CONFIG:RELEASE>:-O3>")
    if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
        add_compile_options("-stdlib=libc++")
    else()
        # nothing special for gcc at the moment
    endif()
endif()</code>

Feature-Based Approach with target_compile_features()

Instead of manually specifying the C standard, modern CMake relies on specifying required features:

<code class="cmake">target_compile_features(HelloWorld PUBLIC cxx_lambda_init_captures)</code>

This allows CMake to determine the necessary compiler flags for supporting the feature.

Multi-Configuration Build Environments

To avoid separate build directories for each compiler and configuration, a wrapper script can compile multiple configurations with an IDE like Visual Studio or a multi-configuration CMake generator.

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