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List:       linux-ppc
Subject:    RE: Compile problems
From:       Steve Revilak <revilak () umbsky ! cc ! umb ! edu>
Date:       2000-07-10 11:46:42
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> I have been trying to compile some c code and running into problems.   I
> finally reduced the problem to how external variables are being handled.

Here is test1.c

> #include <stdio.h>
> extern int a;
> main()
> {
> printf("Hello world\n");
> a=2;
> testfun();
> a=4;
> testfun();
> }

Okay, 'a' is global variable declared to be in some other file.


> And here is test2.c
> extern int a;
> testfun()
> {
> printf("Now got into testfun\n");
> printf("a = %i\n",a);
> }

Again, same thing.  'a' is given global scope and you're telling the
compiler that it's declared somewhere else.


> gcc test1.c test2.c
> and I get the following list of errors:
> /tmp/cca2PpML.o: In function `main':
> /tmp/cca2PpML.o(.text+0x26): undefined reference to `a'

Right.  Because both files are referencing this variable 'a' that isn't
declared anywhere.  Either get rid of the 'extern' in one of the files
or create a header file with a declaration for the variable and #include
it in test1.c and test2.c.

--
Steve Revilak
revilak@umbsky.cc.umb.edu


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