Date: Fri, 19 Aug 1994 04:45:24 -0700 (PDT)
From: "Frederick W. Reimer" <fwreimer AT crl DOT com>
Subject: Re: libraries
To: Kimberley Burchett <OKRA AT max DOT tiac DOT net>
Cc: DJGPP Mailing List <djgpp AT sun DOT soe DOT clarkson DOT edu>

Why you get duplicate names in multiple C translation units that use the 
same header file and include variable definitions:

It's the way C works.  You have declarations and definitions.  In your 
library code, you should have definitions (I think), where you declare 
what type of variable it is AND reserve space for it in the data 
segment.  In your code that uses the library, you only want to declare 
the variables, so the compiler knows what type they are and how much 
space they take up, but you don't want to actually reserve space for them 
in the data segment.

To do this, make "regular" definitions in your library code, like so:
int test;

and make external declarations in your code that uses the library:
extern int test;

Right now, it looks like you are defining the variables in both places, 
asking the compiler to create two spaces in the data segment for the same 
name -- a duplicate definition.

NOTE: I may have gotten definition and declaration backwards, but the 
concept is the same.  Hope this helps.


Fred Reimer

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