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Hello!
I want to include the same headerfile in more than one sourcefile and of course have to take care that each Headerfile is included just once.
I really have no clue, why this works for the Headers provided by Keil but not with my own ones:
#ifndef _MYHEADER_H_ #define _MYHEADER_H_
//Headerfile content . ..
#endif
Obviously the preprocessor includes the Headerfile more than once and so i get errors.
When i add a statement within my Header like:
#warning "included more than once"
the warning message appears twice. (so the header is really included twice).
Can anyone tell me the problem please?!
Kind regards
So in my context i generally would not need it.
Coming from somebody who only just understood what they were ever needed for in the first place, that's a dangerously confident generalization. For the time being, you should follow time-proven coding rules, and one of those is to treat multiple-inclusion guards like your safety belt: don't think about it, just fasten it.
If i now include the Header File of this Lib in more than one .c File, get errors which tells me "Multiple public definitions".
That's got nothing to do with multiple-inclusion guards. It's telling you that you have put stuff in your library's public header that doesn't belong in header files: definitions of variables. In short, some variable declarations in your header are missing the "extern" specifier.
Try a search for those two keywords together - it's been explained before.
See also: c-faq.com/.../decldef.html