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Preprocessor directives

Martin Dold

Hello together,

I'm coding a simple UART-Application on the MCBSTM32 eval board and have problems with the preprocessor directives. I studied the whole documentation here and I'm pretty sure I'm coding in a common way, but still I can't compile my program. These are the very first lines of my main header file:

#ifndef ___MAIN_H_
#define ___MAIN_H_
#endif

#undef EX

#ifndef ___MAIN_C_
  #define EX extern
#else
  #define EX
#endif

And my variables a coded that way:

EX unsigned int ui_TxFrameCounter;

When compiling the program, I get the error code "L6200E: symbol multiply defined" for my variables, because of including the header to other files. I want to declare the variables "extern" for the other header files. Could somebody help me? Would be nice.
Geetings

Parents
  • 0 in reply to edPer Westermark

    Of course I defined in the "MAIN_C_" in the "main.c" file. And you are right with the underscores. In my initial version I tried it without underscores, but without success. That's why I simply tried it this way. But now I removed them again.

    In my opinion the problem comes from the "#define" statement. In the following code line the key word "extern" isn't marked bold in the IDE:

    #ifndef MAIN_C_
  #define EX extern
#else
  #define EX
#endif

    Normally the key word "extern" is displayed as bold text. When I remove the "#define" statement, it is bold again. This is for me an indicator, that there is something wrong.
    Another question by the way: Is German also accepted? ;)
    Greetings

Reply
  • 0 in reply to edPer Westermark

    Of course I defined in the "MAIN_C_" in the "main.c" file. And you are right with the underscores. In my initial version I tried it without underscores, but without success. That's why I simply tried it this way. But now I removed them again.

    In my opinion the problem comes from the "#define" statement. In the following code line the key word "extern" isn't marked bold in the IDE:

    #ifndef MAIN_C_
  #define EX extern
#else
  #define EX
#endif

    Normally the key word "extern" is displayed as bold text. When I remove the "#define" statement, it is bold again. This is for me an indicator, that there is something wrong.
    Another question by the way: Is German also accepted? ;)
    Greetings

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