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Groups > comp.lang.c > #103440
| From | David Brown <david.brown@hesbynett.no> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: How to compile several C files |
| Date | 2017-02-08 11:25 +0100 |
| Organization | A noiseless patient Spider |
| Message-ID | <o7erj0$1ob$1@dont-email.me> (permalink) |
| References | (2 earlier) <af4dd6a4-bfa9-4865-aebb-ea5e0c9c25e2@googlegroups.com> <137458b9-1471-27ef-8c1e-8d9e781f315f@verizon.net> <5b6f9245-8bdf-4365-8a73-201c192f6980@googlegroups.com> <o7cvk5$hmt$1@dont-email.me> <8760klby18.fsf@bsb.me.uk> |
On 07/02/17 20:28, Ben Bacarisse wrote:
> Richard Heathfield <rjh@cpax.org.uk> writes:
> <snip>
>
>> RULE ONE: DO NOT USE FILE SCOPE OBJECTS!
>
> I think it would be better to unravel these intertwined concepts.
> Objects don't have scope, they have lifetime. It's names that have
> scope (and sometimes linkage). What most people call "globals" are
> names of objects defined at file scope. This gives the objects static
> storage duration (even if not declared static) and gives the names (if
> not declared static) external linkage.
There is a big distinction between objects defined at file scope with
"static", and those defined at file scope /without/ "static". The
lifetime is the same, the scope of the identifier is the same, but the
linkage is different.
File static data can often be extremely useful. It lets you have
controlled access to the data from a known set of functions (those in
the same file), without having lots of pointers passed around as
function parameters. It is somewhat like having a singleton class in
C++, with the static data being the data members, static functions being
private methods, and non-static functions being public methods.
"globals" usually (IME) refers to file scope data that is /not/ static,
and thus has external linkage and can be access from other files. That
is when you need to be very wary - any other files can access the data
so you have lost that control. Global data like this is often viewed as
"evil", and that's not a bad first approximation. It can be useful when
used correctly - but you need to be very careful.
Global constant data is much less of a problem, but like non-static
functions the identifiers use a program-wide namespace. Defining a
non-static const array with the name "data" is a bad idea - though it
might be okay for static const data.
>
> It's almost impossible to write C without using objects with static
> storage duration (printf("hello world!\n");) and names with file scope
> are common and not usually frowned upon (enum { ERROR_NO_INPUT = -1 };).
> The problems usually come from using named objects to communicate
> between functions.
>
> I think the best rule is that functions should not modify objects via
> file-scope names. Some may object that this permits reading such data,
> but file-scope data tables are so common that I don't think they can be
> banned by fiat.
>
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How to compile several C files Alla _ <modelling.data@gmail.com> - 2017-02-07 06:10 -0800
Re: How to compile several C files Malcolm McLean <malcolm.mclean5@btinternet.com> - 2017-02-07 07:02 -0800
Re: How to compile several C files David Brown <david.brown@hesbynett.no> - 2017-02-07 16:03 +0100
Re: How to compile several C files Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-02-07 15:06 +0000
Re: How to compile several C files BartC <bc@freeuk.com> - 2017-02-07 15:14 +0000
Re: How to compile several C files Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-02-07 16:02 +0000
Re: How to compile several C files Richard Heathfield <rjh@cpax.org.uk> - 2017-02-07 15:42 +0000
Re: How to compile several C files Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-02-07 16:19 +0000
Re: How to compile several C files Richard Heathfield <rjh@cpax.org.uk> - 2017-02-07 16:40 +0000
Re: How to compile several C files Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-02-07 17:16 +0000
Re: How to compile several C files David Brown <david.brown@hesbynett.no> - 2017-02-08 10:19 +0100
Re: How to compile several C files "James R. Kuyper" <jameskuyper@verizon.net> - 2017-02-07 11:51 -0500
Re: How to compile several C files Alla _ <modelling.data@gmail.com> - 2017-02-07 08:26 -0800
Re: How to compile several C files Richard Heathfield <rjh@cpax.org.uk> - 2017-02-07 16:42 +0000
Re: How to compile several C files Alla _ <modelling.data@gmail.com> - 2017-02-07 10:14 -0800
Re: How to compile several C files vitale.alla@gmail.com - 2017-02-16 09:49 -0800
Re: How to compile several C files Ian Collins <ian-news@hotmail.com> - 2017-02-08 17:35 +1300
Re: How to compile several C files David Brown <david.brown@hesbynett.no> - 2017-02-08 10:28 +0100
Re: How to compile several C files Ian Collins <ian-news@hotmail.com> - 2017-02-08 22:43 +1300
Re: How to compile several C files David Brown <david.brown@hesbynett.no> - 2017-02-08 11:29 +0100
Re: How to compile several C files David Brown <david.brown@hesbynett.no> - 2017-02-08 10:14 +0100
Re: How to compile several C files James Kuyper <jameskuyper@verizon.net> - 2017-02-07 10:07 -0500
Re: How to compile several C files Alla _ <modelling.data@gmail.com> - 2017-02-07 07:56 -0800
Re: How to compile several C files Alla _ <modelling.data@gmail.com> - 2017-02-07 08:24 -0800
Re: How to compile several C files Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-02-07 16:44 +0000
Re: How to compile several C files Alla _ <modelling.data@gmail.com> - 2017-02-07 08:54 -0800
Re: How to compile several C files "James R. Kuyper" <jameskuyper@verizon.net> - 2017-02-07 12:20 -0500
Re: How to compile several C files Alla _ <modelling.data@gmail.com> - 2017-02-07 10:05 -0800
Re: How to compile several C files Richard Heathfield <rjh@cpax.org.uk> - 2017-02-07 18:27 +0000
Re: How to compile several C files Richard Heathfield <rjh@cpax.org.uk> - 2017-02-07 18:40 +0000
Re: How to compile several C files Keith Thompson <kst-u@mib.org> - 2017-02-07 12:22 -0800
Re: How to compile several C files David Brown <david.brown@hesbynett.no> - 2017-02-08 10:33 +0100
Re: How to compile several C files Alla _ <modelling.data@gmail.com> - 2017-02-08 10:25 -0800
Re: How to compile several C files Keith Thompson <kst-u@mib.org> - 2017-02-07 08:58 -0800
Re: How to compile several C files "James R. Kuyper" <jameskuyper@verizon.net> - 2017-02-07 12:07 -0500
Re: How to compile several C files Alla _ <modelling.data@gmail.com> - 2017-02-07 09:14 -0800
Re: How to compile several C files Richard Heathfield <rjh@cpax.org.uk> - 2017-02-07 17:21 +0000
Re: How to compile several C files Alla _ <modelling.data@gmail.com> - 2017-02-07 10:14 -0800
Re: How to compile several C files Alla _ <modelling.data@gmail.com> - 2017-02-07 10:28 -0800
Re: How to compile several C files Richard Heathfield <rjh@cpax.org.uk> - 2017-02-07 18:43 +0000
Re: How to compile several C files Alla _ <modelling.data@gmail.com> - 2017-02-07 10:55 -0800
Re: How to compile several C files Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-02-07 19:28 +0000
Re: How to compile several C files Richard Heathfield <rjh@cpax.org.uk> - 2017-02-07 19:51 +0000
Re: How to compile several C files David Brown <david.brown@hesbynett.no> - 2017-02-08 11:25 +0100
Re: How to compile several C files Richard Heathfield <rjh@cpax.org.uk> - 2017-02-08 12:11 +0000
Re: How to compile several C files David Brown <david.brown@hesbynett.no> - 2017-02-08 14:58 +0100
Re: How to compile several C files Richard Heathfield <rjh@cpax.org.uk> - 2017-02-08 14:23 +0000
Re: How to compile several C files supercat@casperkitty.com - 2017-02-08 07:48 -0800
Re: How to compile several C files Richard Heathfield <rjh@cpax.org.uk> - 2017-02-08 16:09 +0000
Re: How to compile several C files David Brown <david.brown@hesbynett.no> - 2017-02-08 17:23 +0100
Re: How to compile several C files Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-02-08 15:01 +0000
Re: How to compile several C files David Brown <david.brown@hesbynett.no> - 2017-02-08 17:22 +0100
Re: How to compile several C files Keith Thompson <kst-u@mib.org> - 2017-02-08 09:27 -0800
Re: How to compile several C files supercat@casperkitty.com - 2017-02-08 09:51 -0800
Re: How to compile several C files Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-02-08 21:06 +0000
Re: How to compile several C files supercat@casperkitty.com - 2017-02-08 13:20 -0800
Re: How to compile several C files Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-02-08 21:40 +0000
Re: How to compile several C files supercat@casperkitty.com - 2017-02-08 13:49 -0800
Re: How to compile several C files Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-02-08 23:09 +0000
Re: How to compile several C files David Brown <david.brown@hesbynett.no> - 2017-02-08 23:25 +0100
Re: How to compile several C files supercat@casperkitty.com - 2017-02-08 15:17 -0800
Re: How to compile several C files David Brown <david.brown@hesbynett.no> - 2017-02-09 01:17 +0100
Re: How to compile several C files David Brown <david.brown@hesbynett.no> - 2017-02-08 23:19 +0100
Re: How to compile several C files Keith Thompson <kst-u@mib.org> - 2017-02-08 16:44 -0800
Re: How to compile several C files Tim Rentsch <txr@alumni.caltech.edu> - 2017-02-08 22:32 -0800
Re: How to compile several C files Robert Wessel <robertwessel2@yahoo.com> - 2017-02-09 04:03 -0600
Re: How to compile several C files Ian Collins <ian-news@hotmail.com> - 2017-02-10 07:52 +1300
Re: How to compile several C files Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-02-08 12:12 +0000
Re: How to compile several C files BartC <bc@freeuk.com> - 2017-02-08 13:09 +0000
Re: How to compile several C files Malcolm McLean <malcolm.mclean5@btinternet.com> - 2017-02-08 05:14 -0800
Re: How to compile several C files Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-02-08 15:32 +0000
Re: How to compile several C files David Brown <david.brown@hesbynett.no> - 2017-02-08 15:09 +0100
Re: How to compile several C files Keith Thompson <kst-u@mib.org> - 2017-02-07 09:22 -0800
Re: How to compile several C files Gareth Owen <gwowen@gmail.com> - 2017-02-07 18:29 +0000
Re: How to compile several C files bart4858@gmail.com - 2017-02-07 11:05 -0800
Re: How to compile several C files Keith Thompson <kst-u@mib.org> - 2017-02-07 12:26 -0800
Re: How to compile several C files Barry Schwarz <schwarzb@dqel.com> - 2017-02-07 08:34 -0800
Re: How to compile several C files Alla _ <modelling.data@gmail.com> - 2017-02-07 08:57 -0800
Re: How to compile several C files "James R. Kuyper" <jameskuyper@verizon.net> - 2017-02-07 12:29 -0500
Re: How to compile several C files Manfred <noname@invalid.add> - 2017-02-07 19:02 +0100
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