在macOS中使用CMake构建多语言项目的方法咨询

Your approach is conceptually sound, but there are a few bugs and opportunities for improvement that will make this more reliable and maintainable.

Key Issues in the Current Code #

Let's break down the problems first:

• Typo in Objective-C file handling: In the .m case, you're using ${SRC_FILE} (uppercase) instead of the loop variable ${src_file} (lowercase). This variable is undefined, so those files won't get the correct OBJC_FLAGS applied.
• Incorrect regex patterns: The MATCHES checks use patterns like .cpp$, but in regular expressions, the dot (.) matches any character. This means a file named mycpp.txt would incorrectly match .cpp$. You need to escape the dot to match it literally, using double backslashes (since CMake escapes backslashes in strings). The correct pattern for .cpp is "\\.cpp$".
• Potential scope/quoting issues: While not a critical bug here, wrapping the regex pattern in quotes prevents unexpected behavior if your patterns ever include spaces or special characters.

Better Approach: Use CMake's Built-in Language Flags #

Instead of manually checking file extensions and setting per-file properties, CMake has native support for language-specific compilation flags. This is the recommended method because it's less error-prone, automatically applies to all files of the corresponding language, and integrates better with CMake's default behavior.

Here's how to rewrite your flags using CMake's standard variables:

# Append your custom flags to CMake's default flags (don't overwrite them!)
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -arch x86_64")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -arch x86_64 -fmessage-length=0 -std=c++11")
set(CMAKE_OBJC_FLAGS "${CMAKE_OBJC_FLAGS} -fobjc-arc")
set(CMAKE_OBJCXX_FLAGS "${CMAKE_OBJCXX_FLAGS} -std=gnu++11 -stdlib=libc++")

Why This Is Better: #

• No manual extension checks: CMake automatically detects the language for each file based on its extension (.c → C, .cpp → C++, .m → Objective-C, .mm → Objective-C++).
• Preserves default flags: By appending your flags to ${CMAKE_C_FLAGS} instead of overwriting, you keep CMake's default compiler flags (like optimization flags for different build types).
• Maintainable: Adding new files later doesn't require updating any helper functions—they'll get the correct flags automatically.

Corrected Version of Your Original Function (If You Still Need Per-File Control) #

If you have specific cases where you need per-file flags (e.g., overriding global flags for a single file), here's the fixed version of your function:

set(CPP_FLAGS "-x c++ -arch x86_64 -fmessage-length=0 -std=c++11")
set(OBJCPP_FLAGS "-x objective-c++ -std=gnu++11 -stdlib=libc++ ")
set(OBJC_FLAGS "-x objective-c -fobjc-arc")
set(C_FLAGS "-x c -arch x86_64")

function(set_src_files_according_to_language in_source_files)
    foreach(src_file ${in_source_files})
        if(${src_file} MATCHES "\\.cpp$")
            set_source_files_properties(${src_file} PROPERTIES COMPILE_FLAGS "${CPP_FLAGS}")
        elseif(${src_file} MATCHES "\\.mm$")
            set_source_files_properties(${src_file} PROPERTIES COMPILE_FLAGS "${OBJCPP_FLAGS}")
        elseif(${src_file} MATCHES "\\.m$")
            set_source_files_properties(${src_file} PROPERTIES COMPILE_FLAGS "${OBJC_FLAGS}")
        elseif(${src_file} MATCHES "\\.c$")
            set_source_files_properties(${src_file} PROPERTIES COMPILE_FLAGS "${C_FLAGS}")
        endif()
    endforeach()
endfunction()

• Fixed the typo in the .m case.
• Updated regex patterns to escape dots correctly.
• Removed the redundant SRC argument from endforeach (it's optional and inconsistent with the loop variable name).

Content of the question originates from Stack Exchange, asked by Zohar81