Style question: Declaration of globals in header file

From	Steve Keller <keller@no.invalid>
Newsgroups	comp.lang.c
Subject	Style question: Declaration of globals in header file
Date	2017-06-06 19:33 +0200
Organization	Aioe.org NNTP Server
Message-ID	<oh6p0c$e9k$1@gioia.aioe.org> (permalink)

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How do you define & declare global variables in implementation and
header files?  Say you have a compilation unit foo.c that offers
global variables foo and bar that are declared in the header file
foo.h for use by other modules.  The C standard allows the
declarations in the header file to be with or without the extern
storage class specifier, i.e. one could write

    -- foo.h --
    int foo;
    int bar;
    -- foo.c --
    #include "foo.h"
    
    int bar = 1;
    ...
    -----------

or

    -- foo.h --
    extern int foo;
    extern int bar;
    -- foo.c --
    #include "foo.h"
    
    int foo;
    int bar = 1;
    ...
    -----------

I slightly prefer the first variant, since zero-initialized variables
don't need to be defined repeatedly in foo.c, i.e. less maintenance
when name or type needs a change.  OTOH, the second variant states
somewhat more explicitly that the variables are defined elsewhere.

So, what do you usually use in such situations?

Steve

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Style question: Declaration of globals in header file Steve Keller <keller@no.invalid> - 2017-06-06 19:33 +0200
  Re: Style question: Declaration of globals in header file "James R. Kuyper" <jameskuyper@verizon.net> - 2017-06-06 14:21 -0400
    Re: Style question: Declaration of globals in header file Steve Keller <keller@no.invalid> - 2017-06-12 11:07 +0200
      Re: Style question: Declaration of globals in header file bartc <bc@freeuk.com> - 2017-06-12 11:03 +0100
      Re: Style question: Declaration of globals in header file Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-12 11:40 +0100
      Re: Style question: Declaration of globals in header file James Kuyper <jameskuyper@verizon.net> - 2017-06-12 07:33 -0400
        Re: Style question: Declaration of globals in header file Steve Keller <keller@no.invalid> - 2017-06-12 18:00 +0200
          Re: Style question: Declaration of globals in header file "James R. Kuyper" <jameskuyper@verizon.net> - 2017-06-12 12:11 -0400
            Re: Style question: Declaration of globals in header file Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-12 17:27 +0100
          Re: Style question: Declaration of globals in header file Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-12 17:18 +0100
          Re: Style question: Declaration of globals in header file supercat@casperkitty.com - 2017-06-12 09:44 -0700
      Re: Style question: Declaration of globals in header file supercat@casperkitty.com - 2017-06-12 07:55 -0700
        Re: Style question: Declaration of globals in header file Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-12 16:51 +0100
  Re: Style question: Declaration of globals in header file Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-06 19:21 +0100
  Re: Style question: Declaration of globals in header file Jorgen Grahn <grahn+nntp@snipabacken.se> - 2017-06-06 19:54 +0000
  Re: Style question: Declaration of globals in header file Andrey Tarasevich <andreytarasevich@hotmail.com> - 2017-06-06 18:37 -0700
    Re: Style question: Declaration of globals in header file supercat@casperkitty.com - 2017-06-07 07:54 -0700
      Re: Style question: Declaration of globals in header file David Brown <david.brown@hesbynett.no> - 2017-06-07 17:23 +0200
        Re: Style question: Declaration of globals in header file supercat@casperkitty.com - 2017-06-07 11:10 -0700
          Re: Style question: Declaration of globals in header file David Brown <david.brown@hesbynett.no> - 2017-06-07 22:13 +0200
            Re: Style question: Declaration of globals in header file supercat@casperkitty.com - 2017-06-07 14:57 -0700
              Re: Style question: Declaration of globals in header file David Brown <david.brown@hesbynett.no> - 2017-06-08 00:05 +0200
              Re: Style question: Declaration of globals in header file bartc <bc@freeuk.com> - 2017-06-07 23:19 +0100
                Re: Style question: Declaration of globals in header file supercat@casperkitty.com - 2017-06-07 16:16 -0700
              Re: Style question: Declaration of globals in header file Ian Collins <ian-news@hotmail.com> - 2017-06-08 12:56 +1200
                Re: Style question: Declaration of globals in header file David Brown <david.brown@hesbynett.no> - 2017-06-08 08:51 +0200
                Re: Style question: Declaration of globals in header file David Thompson <dave.thompson2@verizon.net> - 2017-07-09 22:43 -0400
                Re: Style question: Declaration of globals in header file supercat@casperkitty.com - 2017-07-10 08:46 -0700
                Re: Style question: Declaration of globals in header file Robert Wessel <robertwessel2@yahoo.com> - 2017-07-10 21:00 -0500
                Re: Style question: Declaration of globals in header file supercat@casperkitty.com - 2017-07-10 21:08 -0700
                Re: Style question: Declaration of globals in header file Robert Wessel <robertwessel2@yahoo.com> - 2017-07-11 01:18 -0500
                Re: Style question: Declaration of globals in header file bartc <bc@freeuk.com> - 2017-06-08 10:10 +0100
                Re: Style question: Declaration of globals in header file raltbos@xs4all.nl (Richard Bos) - 2017-06-17 18:08 +0000
            Re: Style question: Declaration of globals in header file "Patrick.Schluter" <Patrick.Schluter@free.fr> - 2017-06-10 08:36 +0200
    Re: Style question: Declaration of globals in header file Tim Rentsch <txr@alumni.caltech.edu> - 2017-06-09 10:09 -0700
      Re: Style question: Declaration of globals in header file supercat@casperkitty.com - 2017-06-09 12:17 -0700
  Re: Style question: Declaration of globals in header file Tim Rentsch <txr@alumni.caltech.edu> - 2017-06-09 09:52 -0700

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