declarations, definitions and externals

This is a discussion on declarations, definitions and externals within the C Programming forums, part of the General Programming Boards category; I've discussed this somewhat in the C++ part of the forum as well, but I want to discuss the subject ...

  1. #1
    Registered User Drogin's Avatar
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    declarations, definitions and externals

    I've discussed this somewhat in the C++ part of the forum as well, but I want to discuss the subject further in C, so I made a thread here.

    The question is as simple as this:
    If I want to share a global variable over 2 source files, could I just include this headerfile in both my files?
    Code:
    #ifndef MOFF
        #define MOFF
        int test; // Global variable to be used in 2 files
    #endif
    I have compiled it, and it works.
    The question is, is it legal, and more over, is it considered ok as a programming practice?

    I guess part of the question is, is this a declaration or definition?
    Code:
    int test;
    I tried to compile the following program:
    Code:
    int test;
    int test=50;
    int test;
    
    
    int main(int argc, char *argv[]) {
      printf("%d\n", test);
      system("PAUSE");	
      return 0;
    }
    And this compiled, linked and ran..and gave me output "50".

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    and the hat of wrongness Salem's Avatar
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    Registered User Drogin's Avatar
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    Thanks. That helps a lot.

    And now I have to ask, why in the lords name does C allow this kind of code?
    It looks straight out messy.(yeah, I come from C++)

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