How to reference variables declared in codes from header file?

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  1. #1
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    How to reference variables declared in codes from header file?

    Hello,

    I have some inline functions declared in the header file and need to access some variables declared in the codes that include the header file, is there a where to do so?

    For example:
    Code:
    module.h:
    inline t_print() { printf("modid = %d\n", modid); }
    
    // this should print 1 or 2
    inline some_func() { t_print(); };
    
    module1.cpp:
    static long modid = 1;
    t_print();  // this should give modid = 1
    
    module2.cpp:
    static long modid = 2;
    t_print(); // this should give modid = 2
    Any suggestion out there? Thanks.

  2. #2
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    If you have

    #include "module.h"

    in both source files, what do you get?
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  3. #3
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    Thanks for the reply.

    Yes, actually both modules in the example include module.h file. Then when module1.cpp calls some_func(), the printed line should be with "modid = 1"; and when module2.cpp calls some_func(), the printed line would be "modid = 2".

    But since modids are declared as static in the cpp modules, they are not accessible in the header file. Thus the question is whether there is a way, or alternate solution to acheive the similar requirement?

    Thanks again.

  4. #4
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    You should have some_func and t_print take modid as a parameter, that's what parameters are for.

    Otherwise extern might work for you.

  5. #5
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    Yes, passing as argument would solve the situation. I guess that would be the only solution now. Initially the reason I wanted to use static in cpp module was to avoid passing as argument, the programmers need not know about the modid.

    Thank you.

  6. #6
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    Don't complicate things just pass modid as a parameter to the function t_print(). Using global variables can be quite an inconvenience. Your best bet may be to go object oriented and store the globals in their separate modules. That's just a suggestion, though.

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