Static 成员初始化和 Singleton 设计，错误 -> 成员的多重定义

Question

我正在尝试实现 singielton 设计，但不幸的是这个错误发生了多个定义。 一切似乎都很好，我无法在任何地方找到多个定义。 我尝试在 WSL 和 mingw 上使用 gcc 编译它，但问题仍然存在。 我正在关注这个设计https://refactoring.guru/pl/design-patterns/singleton/cpp/example

和成员 static 成员初始化从https://www.tutorialspoint.com/how-to-initialize-private-static-members-in-cplusplus

fsc.hpp

class FileSystemController {
    private:
        const static std::vector<std::pair<uint32_t, uint32_t>> testProfileData;

    protected:
        FileSystemController {};
        static FileSystemController* fsc_;
    public:
        FileSystemController(FileSystemController& other) = delete;    
        void operator=(const FileSystemController&) = delete;    
        static FileSystemController* GetInstance();        
    };

    FileSystemController* FileSystemController::fsc_ = nullptr;
    const std::vector<std::pair<uint32_t, uint32_t>> FileSystemController::testProfileData = {{1001, 2001},
                                                                                              {1002, 2002},
                                                                                              {1003, 2003},
                                                                                              {1004, 2004},
                                                                                              {1005, 2005},
                                                                                              {1006, 2006},
                                                                                              {1007, 2007}};

fsc.cpp

FileSystemController* FileSystemController::GetInstance() {
    if (fsc_ == nullptr) {
        fsc_ = new FileSystemController();
    }
    return fsc_;
}

日志

 ====================[ Build | FileSystemController | Debug ]====================
    /usr/bin/cmake --build /mnt/e/Dokumenty/AiR_rok_4/S7/EngineeringThesis/Profilometr/FileSystemController/cmake-build-debug --target FileSystemController -- -j 8
    Scanning dependencies of target FileSystemController
    [ 25%] Building CXX object CMakeFiles/FileSystemController.dir/FileSystem/FileSystemController.cpp.o
    [ 50%] Linking CXX executable FileSystemController
    /usr/bin/ld: CMakeFiles/FileSystemController.dir/FileSystem/FileSystemController.cpp.o:(.bss+0x0): multiple definition of `controllers::FileSystemController::fsc_'; CMakeFiles/FileSystemController.dir/main.cpp.o:(.bss+0x0): first defined here
    /usr/bin/ld: CMakeFiles/FileSystemController.dir/FileSystem/FileSystemController.cpp.o:(.bss+0x10): multiple definition of `controllers::FileSystemController::testProfileData'; CMakeFiles/FileSystemController.dir/main.cpp.o:(.bss+0x10): first defined here
    collect2: error: ld returned 1 exit status
    make[3]: *** [CMakeFiles/FileSystemController.dir/build.make:114: FileSystemController] Error 1
    make[2]: *** [CMakeFiles/Makefile2:76: CMakeFiles/FileSystemController.dir/all] Error 2
    make[1]: *** [CMakeFiles/Makefile2:83: CMakeFiles/FileSystemController.dir/rule] Error 2
    make: *** [Makefile:118: FileSystemController] Error 2

Answer 1

该 static 变量的声明应在 header 中，即 .cpp 中的定义。

否则，如果您多次包含该文件，编译器将找到多个定义。