Groups > comp.lang.c > #381958

Re: What I've learned in comp.lang.c

From	Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups	comp.lang.c
Subject	Re: What I've learned in comp.lang.c
Date	2024-02-07 10:47 +0000
Organization	A noiseless patient Spider
Message-ID	<87y1bwtuss.fsf@bsb.me.uk> (permalink)
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Malcolm McLean <malcolm.arthur.mclean@gmail.com> writes:

> On 07/02/2024 07:54, David Brown wrote:
>> On 07/02/2024 00:23, Lawrence D'Oliveiro wrote:
>>> On Tue, 6 Feb 2024 09:44:20 +0100, David Brown wrote:
>>>
>>>> They reuse "temp" variables instead of making new ones.
>>>
>>> I like to limit the scope of my temporary variables. In C, this is as
>>> easy
>>> as sticking a pair of braces around a few statements.
>> Generally, you want to have the minimum practical scope for your local
>> variables.  It's rare that you need to add braces just to make a scope
>> for a variable - usually you have enough braces in loops or conditionals
>> - but it happens.
>> 
> The two common patterns are to give each variable the minimum scope, or to
> decare all variables at the start of the function and give them all
> function scope.

The term "function scope" has a specific meaning in C.  Only labels have
function scope.  I know you are not very interested in using exact
terms, but some people might like to know the details.

Since you want to argue for the peculiar (but common) practice of giving
names the largest possible scope (without altering their linkage) you
need a term for the outer-most block scope, but "function scope" is
taken.

> The case for minimum scope is the same as the case for scope itself.

Someone might well misinterpret the term "minimum scope" since it would
require adding lots of otherwise redundant braces.  I *think* you mean
declaring names at the point of first use.  The resulting scope is not
minimum because it often extends beyond the point of last use.

Other people, not familiar with" modern" C, might interpret the term to
mean declaring names at the top of the inner-most appropriate block.

> The
> variable is accessible where it is used and not elsewhere, which makes it
> less likely it will be used in error, and means there are fewer names to
> understand.

The case for declaration at first use is much stronger than this.  It
almost always allows for a meaningful initialisation at the same point,
so the initialisation does not need to be hunted down a checked.  For
me, this is a big win.  (Yes, some people then insist on a dummy
initialisation when the proper one isn't know, but that's a fudge that
is, to my mind, even worse.)

> However there are also strong arguments for ducntion scope. A function is a
> natural unit. Adn all the varibales used in that unit are listed together
> and, ideally, commented. So at a glance you can see what is in scope and
> what is being operated on.

You should not need an inventory of what's being operated on.  Any
function so complex that I can't tell immediately what declaration
corresponds to which name needs to be re-written.  I'd argue that
this is also a big win for "short scopes".  A policy that leads to early
triggers for refactoring is worth considering.

> And there are only three levels of scope. A
> varibale is global, or it is file scope, or it is scoped to the
> function.

You are mixing up scope and lifetime.  C has no "global scope".  A name
may have external linkage (which is probably what you are referring to),
but that is not directly connected to its scope.

> I tend to prefer function scope for C.

We could call it outer-most block scope rather than re-use a term with
an existing, but different, technical meaning.

> However I use a lot of C++ these
> days, and in C++ local scope is often better, and in some cases even
> necessary. So I find that I'm tending to use local scope in C more.

Interesting.  Is it just that using C++ has given you what you would
think of as a bad habit in C, or has using C++ led you to see that your
old preference was not the best one?

-- 
Ben.

Thread

What I've learned in comp.lang.c bart <bc@freeuk.com> - 2024-02-05 01:09 +0000
  Re: What I've learned in comp.lang.c Kaz Kylheku <433-929-6894@kylheku.com> - 2024-02-05 05:58 +0000
    Re: What I've learned in comp.lang.c "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-04 22:49 -0800
      Re: What I've learned in comp.lang.c Kaz Kylheku <433-929-6894@kylheku.com> - 2024-02-05 07:03 +0000
        Re: What I've learned in comp.lang.c "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-04 23:51 -0800
          Re: What I've learned in comp.lang.c "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-04 23:52 -0800
            Re: What I've learned in comp.lang.c Jan van den Broek <balglaas@dds.nl> - 2024-02-05 08:36 +0000
    Re: What I've learned in comp.lang.c Michael S <already5chosen@yahoo.com> - 2024-02-05 18:23 +0200
    Re: What I've learned in comp.lang.c Michael S <already5chosen@yahoo.com> - 2024-02-05 18:32 +0200
      Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-05 20:53 +0100
        Re: What I've learned in comp.lang.c Kaz Kylheku <433-929-6894@kylheku.com> - 2024-02-05 20:53 +0000
          Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-06 09:44 +0100
            Re: What I've learned in comp.lang.c "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-06 01:03 -0800
            Re: What I've learned in comp.lang.c Michael S <already5chosen@yahoo.com> - 2024-02-06 13:41 +0200
              Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-06 13:08 +0100
            Re: What I've learned in comp.lang.c Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-02-06 23:23 +0000
              Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-07 08:54 +0100
                Re: What I've learned in comp.lang.c Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-07 08:59 +0000
                Re: What I've learned in comp.lang.c Ben Bacarisse <ben.usenet@bsb.me.uk> - 2024-02-07 10:47 +0000
                Re: What I've learned in comp.lang.c bart <bc@freeuk.com> - 2024-02-07 11:04 +0000
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-07 14:21 +0100
                Re: What I've learned in comp.lang.c bart <bc@freeuk.com> - 2024-02-07 14:24 +0000
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-07 21:30 +0100
                Re: What I've learned in comp.lang.c Ben Bacarisse <ben.usenet@bsb.me.uk> - 2024-02-07 15:36 +0000
                Re: What I've learned in comp.lang.c bart <bc@freeuk.com> - 2024-02-07 18:05 +0000
                Re: What I've learned in comp.lang.c scott@slp53.sl.home (Scott Lurndal) - 2024-02-07 18:26 +0000
                Re: What I've learned in comp.lang.c bart <bc@freeuk.com> - 2024-02-07 19:53 +0000
                Re: What I've learned in comp.lang.c Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-02-07 21:38 +0000
                Re: What I've learned in comp.lang.c Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-08 00:29 +0000
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-07 21:37 +0100
                Re: What I've learned in comp.lang.c bart <bc@freeuk.com> - 2024-02-07 22:52 +0000
                Re: What I've learned in comp.lang.c Kaz Kylheku <433-929-6894@kylheku.com> - 2024-02-08 01:13 +0000
                Re: What I've learned in comp.lang.c bart <bc@freeuk.com> - 2024-02-08 02:09 +0000
                Re: What I've learned in comp.lang.c Kaz Kylheku <433-929-6894@kylheku.com> - 2024-02-08 03:07 +0000
                Re: What I've learned in comp.lang.c bart <bc@freeuk.com> - 2024-02-08 14:17 +0000
                Re: What I've learned in comp.lang.c Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-02-08 16:02 -0800
                Re: What I've learned in comp.lang.c bart <bc@freeuk.com> - 2024-02-09 00:48 +0000
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-09 08:53 +0100
                Re: What I've learned in comp.lang.c Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-02-10 21:55 -0800
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-08 13:01 +0100
                Re: What I've learned in comp.lang.c Ben Bacarisse <ben.usenet@bsb.me.uk> - 2024-02-08 11:37 +0000
                Re: What I've learned in comp.lang.c Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-08 12:10 +0000
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-08 13:24 +0100
                Re: What I've learned in comp.lang.c Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-08 13:03 +0000
                Re: What I've learned in comp.lang.c bart <bc@freeuk.com> - 2024-02-08 13:17 +0000
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-08 16:52 +0100
                Re: What I've learned in comp.lang.c Ben Bacarisse <ben.usenet@bsb.me.uk> - 2024-02-08 17:17 +0000
                Re: What I've learned in comp.lang.c Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-02-09 14:50 -0800
                Re: What I've learned in comp.lang.c Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-07 12:44 +0000
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-07 14:49 +0100
                Re: What I've learned in comp.lang.c Ben Bacarisse <ben.usenet@bsb.me.uk> - 2024-02-07 16:13 +0000
                Re: What I've learned in comp.lang.c Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-02-07 08:21 -0800
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-07 14:01 +0100
                Re: What I've learned in comp.lang.c Richard Harnden <richard.nospam@gmail.invalid> - 2024-02-07 13:21 +0000
                Re: What I've learned in comp.lang.c Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-07 13:42 +0000
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-07 16:17 +0100
                Re: What I've learned in comp.lang.c Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-02-07 21:34 +0000
                Re: What I've learned in comp.lang.c scott@slp53.sl.home (Scott Lurndal) - 2024-02-07 16:21 +0000
                Re: What I've learned in comp.lang.c Michael S <already5chosen@yahoo.com> - 2024-02-08 13:26 +0200
                Re: What I've learned in comp.lang.c Ben Bacarisse <ben.usenet@bsb.me.uk> - 2024-02-07 10:04 +0000
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-07 14:51 +0100
                Re: What I've learned in comp.lang.c Ben Bacarisse <ben.usenet@bsb.me.uk> - 2024-02-07 15:30 +0000
                Re: What I've learned in comp.lang.c Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-07 15:45 +0000
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-07 21:44 +0100
                Re: What I've learned in comp.lang.c Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-08 00:33 +0000
                Re: What I've learned in comp.lang.c Kaz Kylheku <433-929-6894@kylheku.com> - 2024-02-08 01:30 +0000
                Re: What I've learned in comp.lang.c Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-02-08 01:38 +0000
                Re: What I've learned in comp.lang.c Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-08 02:21 +0000
                Re: What I've learned in comp.lang.c Kaz Kylheku <433-929-6894@kylheku.com> - 2024-02-08 03:07 +0000
                Re: What I've learned in comp.lang.c Ben Bacarisse <ben.usenet@bsb.me.uk> - 2024-02-08 11:45 +0000
                Re: What I've learned in comp.lang.c Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-08 12:15 +0000
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-08 13:29 +0100
                Re: What I've learned in comp.lang.c Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-08 12:55 +0000
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-09 09:02 +0100
                Re: What I've learned in comp.lang.c scott@slp53.sl.home (Scott Lurndal) - 2024-02-08 16:09 +0000
                Re: What I've learned in comp.lang.c Richard Harnden <richard.nospam@gmail.invalid> - 2024-02-08 16:28 +0000
                Re: What I've learned in comp.lang.c Ben Bacarisse <ben.usenet@bsb.me.uk> - 2024-02-08 17:13 +0000
                Re: What I've learned in comp.lang.c Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-02-08 17:53 -0800
    Re: What I've learned in comp.lang.c Michael S <already5chosen@yahoo.com> - 2024-02-05 19:02 +0200
      Re: What I've learned in comp.lang.c Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-02-05 23:28 +0000
        Re: What I've learned in comp.lang.c Richard Harnden <richard.nospam@gmail.invalid> - 2024-02-05 23:40 +0000
        Re: What I've learned in comp.lang.c Michael S <already5chosen@yahoo.com> - 2024-02-06 01:46 +0200
          Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-06 09:54 +0100
        Re: What I've learned in comp.lang.c "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-05 16:03 -0800
          Re: What I've learned in comp.lang.c "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-05 16:06 -0800
        Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-06 09:50 +0100
          Re: What I've learned in comp.lang.c "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-06 01:01 -0800
          Re: What I've learned in comp.lang.c Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-02-06 23:24 +0000
            Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-07 08:56 +0100
              Re: What I've learned in comp.lang.c Michael S <already5chosen@yahoo.com> - 2024-02-07 12:09 +0200
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-07 15:03 +0100
              Re: What I've learned in comp.lang.c scott@slp53.sl.home (Scott Lurndal) - 2024-02-07 16:25 +0000
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-07 21:49 +0100
                Re: What I've learned in comp.lang.c "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-07 13:04 -0800
                Re: What I've learned in comp.lang.c Michael S <already5chosen@yahoo.com> - 2024-02-07 23:37 +0200
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-08 08:52 +0100
                Re: What I've learned in comp.lang.c Michael S <already5chosen@yahoo.com> - 2024-02-09 15:55 +0200
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-09 15:29 +0100
                Re: What I've learned in comp.lang.c Michael S <already5chosen@yahoo.com> - 2024-02-09 16:52 +0200
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-09 17:22 +0100
                Re: What I've learned in comp.lang.c Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-02-10 07:18 +0000
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-10 17:11 +0100
                Re: What I've learned in comp.lang.c Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-02-10 21:23 +0000
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-11 14:01 +0100
                Re: What I've learned in comp.lang.c Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-02-07 21:41 +0000
    Re: What I've learned in comp.lang.c bart <bc@freeuk.com> - 2024-02-07 02:18 +0000
      Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-07 09:30 +0100
      Re: What I've learned in comp.lang.c Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-07 09:04 +0000
      Re: What I've learned in comp.lang.c Kaz Kylheku <433-929-6894@kylheku.com> - 2024-02-07 23:24 +0000
        Re: What I've learned in comp.lang.c bart <bc@freeuk.com> - 2024-02-08 01:46 +0000
          Re: What I've learned in comp.lang.c Kaz Kylheku <433-929-6894@kylheku.com> - 2024-02-08 02:50 +0000
            Re: What I've learned in comp.lang.c bart <bc@freeuk.com> - 2024-02-08 11:08 +0000
            Re: What I've learned in comp.lang.c Michael S <already5chosen@yahoo.com> - 2024-02-08 13:10 +0200
              Re: What I've learned in comp.lang.c Kaz Kylheku <433-929-6894@kylheku.com> - 2024-02-08 17:48 +0000
                Re: What I've learned in comp.lang.c Michael S <already5chosen@yahoo.com> - 2024-02-08 21:30 +0200
                Re: What I've learned in comp.lang.c bart <bc@freeuk.com> - 2024-02-08 20:39 +0000
                Re: What I've learned in comp.lang.c "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-08 13:39 -0800
                Re: What I've learned in comp.lang.c Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-02-08 14:18 -0800
                Re: What I've learned in comp.lang.c gazelle@shell.xmission.com (Kenny McCormack) - 2024-02-08 22:29 +0000
                Re: What I've learned in comp.lang.c "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-08 14:43 -0800
                Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-09 09:12 +0100
  Re: What I've learned in comp.lang.c Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-02-04 23:36 -0800
    Re: What I've learned in comp.lang.c scott@slp53.sl.home (Scott Lurndal) - 2024-02-05 14:52 +0000
      Re: What I've learned in comp.lang.c gazelle@shell.xmission.com (Kenny McCormack) - 2024-02-05 22:58 +0000
    Re: What I've learned in comp.lang.c Jim Jackson <jj@franjam.org.uk> - 2024-02-05 18:01 +0000
  Re: What I've learned in comp.lang.c Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-05 08:29 +0000
    Re: What I've learned in comp.lang.c bart <bc@freeuk.com> - 2024-02-07 01:35 +0000
      Re: What I've learned in comp.lang.c Kaz Kylheku <433-929-6894@kylheku.com> - 2024-02-07 02:26 +0000
        Re: What I've learned in comp.lang.c bart <bc@freeuk.com> - 2024-02-07 10:47 +0000
  Re: What I've learned in comp.lang.c Dan Purgert <dan@djph.net> - 2024-02-05 11:03 +0000
  Re: What I've learned in comp.lang.c David Brown <david.brown@hesbynett.no> - 2024-02-05 13:15 +0100
    Re: What I've learned in comp.lang.c Ben Bacarisse <ben.usenet@bsb.me.uk> - 2024-02-05 14:09 +0000
  Re: What I've learned in comp.lang.c Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-02-05 23:29 +0000

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