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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
In one of your source files, you should define __MAIN_C_ before including your header file. How else will the header file know when to use "extern" or not?
By the way - you should consider using symbols without any leading underscore. You are neither the C standard maintainer nor the compiler vendor...
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