Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #112127

Re: Scope of identifiers

Show key headers only | View raw

David Kleinecke <dkleinecke@gmail.com> writes:
> On Monday, June 12, 2017 at 1:19:09 PM UTC-7, Keith Thompson wrote:
[...]
>> What I proposed was to replace the current definition of "same scope"
>> (which is problematic because two non-identical scopes can be the "same
>> scope") by something like "matching scope".  (I'm open to a better
>> adjective than "matching".)  I think that solves the (minor) problem of
>> "same scope" being confusing, it doesn't add to the number of defined
>> terms, and it's a fairly minimal change.
>
> If one looks at the case of block scope and the old C approach
> one observes that all the declarations come before the statements.
> If one thinks of "starting" a scope extends through all the
> declarations then a single concept of "scope" holds.
>
> This observation doesn't help the present day situation but it does
> help explain how the situation cam about.

Given:

    {
        int a = 10;
        int b = a;
        int c = d; /* illegal */
        int d = 20;
        /* statements ... */
    }

the initialization of c is invalid because the scope of d doesn't start
until the line on which it's defined.

The lifetimes of all 4 objects begin at the same time, when
execution reaches the opening "{", but their scopes begin at 4
different locations.  All 4 scopes are the "same scope" as the
standard defines that phrase.  (Scope is a compile-time concept;
lifetime is a run-time concept.)

[...]

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Scope of identifiers Steve Keller <keller@no.invalid> - 2017-06-12 18:08 +0200
  Re: Scope of identifiers "James R. Kuyper" <jameskuyper@verizon.net> - 2017-06-12 12:22 -0400
    Re: Scope of identifiers Keith Thompson <kst-u@mib.org> - 2017-06-12 09:39 -0700
  Re: Scope of identifiers Keith Thompson <kst-u@mib.org> - 2017-06-12 09:38 -0700
    Re: Scope of identifiers "James R. Kuyper" <jameskuyper@verizon.net> - 2017-06-12 14:41 -0400
      Re: Scope of identifiers Keith Thompson <kst-u@mib.org> - 2017-06-12 12:39 -0700
        Re: Scope of identifiers "James R. Kuyper" <jameskuyper@verizon.net> - 2017-06-12 15:53 -0400
          Re: Scope of identifiers Keith Thompson <kst-u@mib.org> - 2017-06-12 13:19 -0700
            Re: Scope of identifiers David Kleinecke <dkleinecke@gmail.com> - 2017-06-13 11:01 -0700
              Re: Scope of identifiers jameskuyper@verizon.net - 2017-06-13 11:25 -0700
              Re: Scope of identifiers Keith Thompson <kst-u@mib.org> - 2017-06-13 12:16 -0700
                Re: Scope of identifiers David Kleinecke <dkleinecke@gmail.com> - 2017-06-13 21:02 -0700
                Re: Scope of identifiers Ian Collins <ian-news@hotmail.com> - 2017-06-14 21:53 +1200
                Re: Scope of identifiers supercat@casperkitty.com - 2017-06-14 08:10 -0700
                Re: Scope of identifiers Keith Thompson <kst-u@mib.org> - 2017-06-14 09:19 -0700
                Re: Scope of identifiers supercat@casperkitty.com - 2017-06-14 10:14 -0700
                Re: Scope of identifiers Keith Thompson <kst-u@mib.org> - 2017-06-14 09:12 -0700
  Re: Scope of identifiers Robert Wessel <robertwessel2@yahoo.com> - 2017-06-12 13:02 -0500

csiph-web