Re: Inline functions and locals

From	James Kuyper <jameskuyper@alumni.caltech.edu>
Newsgroups	comp.lang.c++
Subject	Re: Inline functions and locals
Date	2022-01-14 08:34 -0500
Organization	A noiseless patient Spider
Message-ID	<srru5t$939$1@dont-email.me> (permalink)
References	<srmvu4$oie$1@gioia.aioe.org> <srqkvk$3vi$1@dont-email.me> <srrmd6$1bo0$1@gioia.aioe.org>

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On 1/14/22 6:22 AM, Muttley@dastardlyhq.com wrote:
> On Thu, 13 Jan 2022 17:51:45 -0800
> Andrey Tarasevich <andreytarasevich@hotmail.com> wrote:
...
>> Um... You are seriously confused. This is a rather widespread 
>> misconception that keyword `inline` has something to do with "inlining" 
>> function code at the call site.
>>
>> 1. "Declaring function as inline" and "embedding (inlining) function 
>> code at a specific call site" are two completely different, independent, 
>> unrelated things. In your example you simply declared a function as 
> 
> Wikipedia says otherwise:
> 
> https://en.wikipedia.org/wiki/Inline_function
> 
> "It serves as a compiler directive that suggests (but does not require) that 
> the compiler substitute the body of the function inline by performing inline 
> expansion, i.e. by inserting the function code at the address of each function 
> call,"

Wikipedia is a good source in general, and particularly for
computer-related stuff, but it isn't as authoritative as the C++
standard itself:

"... The inline specifier indicates to the implementation that inline
substitution of the function body at the point of call is to be
preferred to the usual function call mechanism. An implementation is not
required to perform this inline substitution at the point of call;
however, even if this inline substitution is omitted, the other rules
for inline functions specified in this subclause shall still be
respected. ..." (9.2.7p2)

Note that inline substitution, which he denies has anything to do with
the inline keyword, is in fact the primary thing that the description of
that keyword is concerned with. There's lots of other things that the
standard says about 'inline' in other sections of the standard, and it's
those other things that he's talking about, but all of those other
things are written merely to support the primary purpose of 'inline'.
There are other ways to get around the ODR rule that don't involve the
'inline' keyword.

> Perhaps you're the one who's getting confused?

He's not confused, he just doesn't approve of what the standard says
about "inline", and therefore deliberately misrepresents it. The
standard's wording above makes "inline" no more than a hint. An
implementation is free to perform inline substitution of any function
call, whether or not the function is declared 'inline', so long as the
result produces the same observable effects as calling a separate
function. Many implementations don't even implement 'inline' as a hint,
completely ignoring it when deciding whether or not to perform inline
substitution. That's why he pretends that the wording I've quoted above
doesn't exist.

The problem with your code is not that inline substitution isn't being
done (though that is a possibility), it's that you have incorrect
expectations about what the result of that substitution would be.
Whether inlined or not, the object named 's' is in a separate block from
the function call itself, and therefore has a lifetime that ends when
the end of that block is reached. Whether or not the function is
inlined, that occurs before your code uses the reference to 's'.

Thread

Inline functions and locals Muttley@dastardlyhq.com - 2022-01-12 16:34 +0000
  Re: Inline functions and locals Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-12 17:38 +0100
  Re: Inline functions and locals James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-12 12:47 -0500
  Re: Inline functions and locals Juha Nieminen <nospam@thanks.invalid> - 2022-01-13 07:00 +0000
    Re: Inline functions and locals "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-01-13 10:45 +0100
      Re: Inline functions and locals Juha Nieminen <nospam@thanks.invalid> - 2022-01-17 12:55 +0000
        Re: Inline functions and locals David Brown <david.brown@hesbynett.no> - 2022-01-17 15:14 +0100
        Re: Inline functions and locals Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-17 10:24 -0800
          Re: Inline functions and locals David Brown <david.brown@hesbynett.no> - 2022-01-17 19:46 +0100
    Re: Inline functions and locals Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-13 11:08 +0100
      Re: Inline functions and locals Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-13 19:30 -0800
  Re: Inline functions and locals Paavo Helde <eesnimi@osa.pri.ee> - 2022-01-13 12:46 +0200
    Re: Inline functions and locals Muttley@dastardlyhq.com - 2022-01-13 15:38 +0000
  Re: Inline functions and locals Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-13 17:51 -0800
    Re: Inline functions and locals Muttley@dastardlyhq.com - 2022-01-14 11:22 +0000
      Re: Inline functions and locals Öö Tiib <ootiib@hot.ee> - 2022-01-14 04:02 -0800
        Re: Inline functions and locals Manfred <invalid@invalid.add> - 2022-01-14 17:30 +0100
          Re: Inline functions and locals Muttley@dastardlyhq.com - 2022-01-14 16:49 +0000
        Re: Inline functions and locals Muttley@dastardlyhq.com - 2022-01-14 16:40 +0000
          Re: Inline functions and locals Öö Tiib <ootiib@hot.ee> - 2022-01-14 11:28 -0800
          Re: Inline functions and locals "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-01-14 20:29 +0100
      Re: Inline functions and locals James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-14 08:34 -0500
        Re: Inline functions and locals James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-14 11:26 -0500
          Re: Inline functions and locals David Brown <david.brown@hesbynett.no> - 2022-01-14 18:47 +0100
      Re: Inline functions and locals Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-14 08:43 -0800
        Re: Inline functions and locals Juha Nieminen <nospam@thanks.invalid> - 2022-01-17 05:38 +0000
          Re: Inline functions and locals David Brown <david.brown@hesbynett.no> - 2022-01-17 08:12 +0100
            Re: Inline functions and locals "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-01-16 23:51 -0800
              Re: Inline functions and locals "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-01-16 23:55 -0800
              Re: Inline functions and locals David Brown <david.brown@hesbynett.no> - 2022-01-17 11:35 +0100
            Re: Inline functions and locals Juha Nieminen <nospam@thanks.invalid> - 2022-01-17 09:50 +0000
              Re: Inline functions and locals James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-17 14:39 -0500
                Re: Inline functions and locals Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-17 15:34 -0800
                Re: Inline functions and locals "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2022-01-17 15:50 -0800
                Re: Inline functions and locals Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-04-25 03:42 -0700
                Re: Inline functions and locals "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2022-04-25 08:48 -0700
          Re: Inline functions and locals Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-16 23:53 -0800
            Re: Inline functions and locals Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-17 15:29 -0800
    Re: Inline functions and locals Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-17 12:40 +0100
      Re: Inline functions and locals Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-17 10:13 -0800
        Re: Inline functions and locals James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-17 16:15 -0500
          Re: Inline functions and locals Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-17 16:28 -0800
            Re: Inline functions and locals James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-17 22:55 -0500
              Re: Inline functions and locals Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-18 11:32 -0800
                Re: Inline functions and locals James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-18 19:03 -0500
                Re: Inline functions and locals Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-18 17:22 -0800
        Re: Inline functions and locals Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-18 09:20 +0100

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