Re: To include or not to include

From	BartC <bc@freeuk.com>
Newsgroups	comp.lang.c
Subject	Re: To include or not to include
Date	2016-09-25 18:05 +0100
Organization	A noiseless patient Spider
Message-ID	<ns904g$eb$1@dont-email.me> (permalink)
References	(5 earlier) <87a8ewgb5y.fsf@bsb.me.uk> <ns76j2$7eh$1@dont-email.me> <87r388dzw9.fsf@bsb.me.uk> <ns8lku$r18$1@dont-email.me> <ns8rln$f99$1@jstuckle.eternal-september.org>

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On 25/09/2016 16:49, Jerry Stuckle wrote:
> On 9/25/2016 10:06 AM, BartC wrote:

>> But global functions, global typedefs, global struct tags, global enum
>> names, global #defines and global #includes (ie. module names) are still
>> acceptable? It could get tricky otherwise.
>>
>> What about file-scope data objects; are they also frowned upon?

> A big difference between a global variable and global functions,
> typedefs, etc.
>
> The main reason to avoid global variables is simple - program
> reliability.  Let's say you have a global "foo" of type int.  Valid
> values are between 0 and 10.
>
> At one point in your program, you find it occasionally gets a value like
> 423910863407.  How did it get there?

Maybe someone defined a file-scope variable and forgot to stick 'static' 
in front?

But what about globals that have 'const' in front (such as large 
read-only tables); they will be protected surely?

And of course if you have a function F() shared between modules A and B, 
nothing stops module X from calling it.

> If it's a global variable, that could have happened anywhere in the
> program.  What if your program is 500K lines long?
>
> File scope is better, because only functions in the file can access the
> variable (barring, of course, memory corruption).  That at least limits
> the impact.

Suppose you need to split one module into two. Then you will need start 
using globals to share file-scope variables between the two.

> With that said, sometimes you still need to use globals, especially in
> kernel programming when using multiple threads.

Everyone can find their own examples where they are indispensable.

-- 
Bartc

Thread

To include or not to include James Harris <james.harris.1@gmail.com> - 2016-09-23 10:45 +0100
  Re: To include or not to include David Brown <david.brown@hesbynett.no> - 2016-09-23 12:43 +0200
    Re: To include or not to include BartC <bc@freeuk.com> - 2016-09-23 12:17 +0100
      Re: To include or not to include Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-23 13:32 +0100
        Re: To include or not to include David Brown <david.brown@hesbynett.no> - 2016-09-23 14:57 +0200
        Re: To include or not to include BartC <bc@freeuk.com> - 2016-09-24 20:34 +0100
          Re: To include or not to include Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-24 23:55 +0100
            Re: To include or not to include BartC <bc@freeuk.com> - 2016-09-25 01:43 +0100
              Re: To include or not to include Ian Collins <ian-news@hotmail.com> - 2016-09-25 14:38 +1300
              Re: To include or not to include Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-25 11:42 +0100
                Re: To include or not to include BartC <bc@freeuk.com> - 2016-09-25 11:58 +0100
                Re: To include or not to include James Harris <james.harris.1@gmail.com> - 2016-09-25 14:06 +0100
                Re: To include or not to include BartC <bc@freeuk.com> - 2016-09-25 15:15 +0100
                Re: To include or not to include Reinhardt Behm <rbehm@hushmail.com> - 2016-09-25 23:33 +0800
                Re: To include or not to include Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2016-09-25 10:04 -0600
                Re: To include or not to include Reinhardt Behm <rbehm@hushmail.com> - 2016-09-26 00:21 +0800
                Re: To include or not to include "James R. Kuyper" <jameskuyper@verizon.net> - 2016-09-25 13:17 -0400
                Re: To include or not to include James Harris <james.harris.1@gmail.com> - 2016-09-26 00:18 +0100
                Re: To include or not to include BartC <bc@freeuk.com> - 2016-09-26 17:55 +0100
                Re: To include or not to include Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-26 20:07 +0100
                Re: To include or not to include supercat@casperkitty.com - 2016-09-26 12:13 -0700
                Re: To include or not to include James Harris <james.harris.1@gmail.com> - 2016-09-27 01:25 +0100
                Re: To include or not to include supercat@casperkitty.com - 2016-09-26 18:05 -0700
                Re: To include or not to include Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-27 14:27 +0100
                Re: To include or not to include BartC <bc@freeuk.com> - 2016-09-27 14:49 +0100
                Re: To include or not to include Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-27 15:15 +0100
                Re: To include or not to include Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-27 07:42 -0700
                Re: To include or not to include Keith Thompson <kst-u@mib.org> - 2016-09-27 09:30 -0700
                Re: To include or not to include Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-27 10:06 -0700
                Re: To include or not to include supercat@casperkitty.com - 2016-09-27 08:12 -0700
                Re: To include or not to include Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-28 10:46 -0700
                Re: To include or not to include BartC <bc@freeuk.com> - 2016-09-27 17:55 +0100
                Re: To include or not to include supercat@casperkitty.com - 2016-09-27 10:19 -0700
                Re: To include or not to include Keith Thompson <kst-u@mib.org> - 2016-09-27 11:42 -0700
                Re: To include or not to include BartC <bc@freeuk.com> - 2016-09-27 19:57 +0100
                Re: To include or not to include Keith Thompson <kst-u@mib.org> - 2016-09-27 12:38 -0700
                Re: To include or not to include BartC <bc@freeuk.com> - 2016-09-27 21:00 +0100
                Re: To include or not to include Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-28 01:50 +0100
                Re: To include or not to include BartC <bc@freeuk.com> - 2016-09-28 10:55 +0100
                Re: To include or not to include Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-27 13:33 -0700
                Re: To include or not to include Ike Naar <ike@iceland.freeshell.org> - 2016-09-28 19:13 +0000
                Re: To include or not to include supercat@casperkitty.com - 2016-09-27 12:38 -0700
                Re: To include or not to include James Harris <james.harris.1@gmail.com> - 2016-09-27 20:57 +0100
                Re: To include or not to include supercat@casperkitty.com - 2016-09-27 07:25 -0700
                Re: To include or not to include Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-28 00:28 +0100
                Re: To include or not to include supercat@casperkitty.com - 2016-09-30 07:53 -0700
                Re: To include or not to include Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-30 16:06 +0100
                Re: To include or not to include Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-27 13:53 +0100
                Re: To include or not to include James Harris <james.harris.1@gmail.com> - 2016-09-30 19:46 +0100
                Re: To include or not to include Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-30 20:27 +0100
                Re: To include or not to include Reinhardt Behm <rbehm@hushmail.com> - 2016-09-25 23:27 +0800
                Re: To include or not to include Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-25 11:38 -0400
                Re: To include or not to include Reinhardt Behm <rbehm@hushmail.com> - 2016-09-25 23:40 +0800
                Re: To include or not to include BartC <bc@freeuk.com> - 2016-09-25 15:06 +0100
                Re: To include or not to include Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-25 11:49 -0400
                Re: To include or not to include BartC <bc@freeuk.com> - 2016-09-25 18:05 +0100
                Re: To include or not to include Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-25 16:42 -0400
                Re: To include or not to include BartC <bc@freeuk.com> - 2016-09-25 21:53 +0100
                Re: To include or not to include Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-25 17:57 -0400
                Re: To include or not to include Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-25 21:20 +0100
                Re: To include or not to include BartC <bc@freeuk.com> - 2016-09-25 21:49 +0100
                Re: To include or not to include Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-26 00:40 +0100
      Re: To include or not to include David Brown <david.brown@hesbynett.no> - 2016-09-23 14:56 +0200
  Re: To include or not to include Richard Heathfield <rjh@cpax.org.uk> - 2016-09-23 13:31 +0100
    Re: To include or not to include James Harris <james.harris.1@gmail.com> - 2016-09-23 13:52 +0100
      Re: To include or not to include Richard Heathfield <rjh@cpax.org.uk> - 2016-09-23 14:35 +0100
    Re: To include or not to include Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-23 18:55 +0100
      Re: To include or not to include Richard Heathfield <rjh@cpax.org.uk> - 2016-09-23 20:33 +0100
  Re: To include or not to include Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2016-09-23 08:22 -0600
  Re: To include or not to include Richard Damon <Richard@Damon-Family.org> - 2016-09-23 11:37 -0400

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