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From: slewis@aerospace.aero.org (Steven Lewis)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Link error : multiply defined variables in THINK C
Message-ID: <80424@aerospace.AERO.ORG>
Date: 8 Aug 90 17:06:23 GMT
References: <12725@june.cs.washington.edu>
Sender: news@aerospace.aero.org
Reply-To: slewis@antares.UUCP (Steven Lewis)
Organization: The Aerospace Corporation, El Segundo, CA
Lines: 24

In article <12725@june.cs.washington.edu> ginting@fred.cs.washington.edu (Eka Namara Ginting) writes:
>
>  I'm writing a program that has two source files (.c) that import
>  a common .h file. This .h file includes another .h file that contains
>  some variable declarations. When I try to run this program, THINK C
>  compiler complains with "link failed : multiply defined variables" and 
>  gives me the list of variables that I declared in the second .h file
>  (the one included by the other .h file). These variables are of type
>  unsigned long, not initialized, nor of class static.
>
Did you declare the variables extern in the header file??
failure to do so will cause definition in both files.
another trick is to do something like this:

#undef EXTERN /* make sure this not done earlier */
#ifdef FOO  /* something defined in only one file */
#define EXTERN  /* This actually declares the variable */
#else
#define EXTERN extern /* only make extern call */
#endif FOO
  Now declare all variables EXTERN

also make sure your #ifndef statements are done correctly
while THINK_C