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我正在寻找允许在另一个类的头文件中进行类的前向声明的定义:

我是否允许为基类,作为成员持有的类,通过引用传递给成员函数的类等执行此操作？

我正在阅读Meyers编写的"Effective C++",并且遇到了"翻译单元"一词.

有人可以给我一个解释:

1)究竟是什么

2)在使用C++编程时,我应该何时考虑使用它

3)如果它只与C++有关,或者它可以与其他编程语言一起使用

我可能已经在不知道术语的情况下使用它了....

如果我在classB.h和classC.h中包含类定义文件classA.h,那么如果classD.h同时包含classB.h和classC.h,那么是否会有类重定义？

我正在写一个H264解析器(没有OO),但我正在尝试使用一些模块来组织更好的东西.

我遇到了这个问题:

`CMakeFiles/server.dir/mainclass.cpp.o:(.bss+0x0): multiple definition of `I_Macroblock_Modes'  
`CMakeFiles/server.dir/main.cpp.o:(.bss+0x0): first defined here  
`CMakeFiles/server.dir/mainclass.cpp.o:(.bss+0x300): multiple definition of `P_and_SP_macroblock_modes'  
`CMakeFiles/server.dir/main.cpp.o:(.bss+0x300): first defined here  
`CMakeFiles/server.dir/mainclass.cpp.o:(.bss+0x680): multiple definition of `B_Macroblock_Modes' 
`CMakeFiles/server.dir/main.cpp.o:(.bss+0x680): first defined here  
`CMakeFiles/server.dir/thRunAppl.cpp.o:(.bss+0x0): multiple definition of `I_Macroblock_Modes'  
`CMakeFiles/server.dir/main.cpp.o:(.bss+0x0): first defined here  
`CMakeFiles/server.dir/thRunAppl.cpp.o:(.bss+0x300): multiple definition of `P_and_SP_macroblock_modes'  
`CMakeFiles/server.dir/main.cpp.o:(.bss+0x300): first defined here  
`CMakeFiles/server.dir/thRunAppl.cpp.o:(.bss+0x680): multiple definition of `B_Macroblock_Modes'  
`CMakeFiles/server.dir/main.cpp.o:(.bss+0x680): first defined here  
`CMakeFiles/server.dir/h.264parser.cpp.o:(.bss+0x0): multiple definition of `I_Macroblock_Modes'  
`CMakeFiles/server.dir/main.cpp.o:(.bss+0x0): first defined here  
`CMakeFiles/server.dir/h.264parser.cpp.o:(.bss+0x300): multiple definition of `P_and_SP_macroblock_modes'  
`CMakeFiles/server.dir/main.cpp.o:(.bss+0x300): first defined here  
`CMakeFiles/server.dir/h.264parser.cpp.o:(.bss+0x680): multiple definition of `B_Macroblock_Modes'  
`CMakeFiles/server.dir/main.cpp.o:(.bss+0x680): …