Re: A way around _HAS_ITERATOR_DEBUGGING

From	Bonita Montero <Bonita.Montero@gmail.com>
Newsgroups	comp.lang.c++
Subject	Re: A way around _HAS_ITERATOR_DEBUGGING
Date	2021-06-02 15:12 +0200
Organization	A noiseless patient Spider
Message-ID	<s9804o$c84$1@dont-email.me> (permalink)
References	<s97uob$306$1@dont-email.me> <s97vq0$a0t$1@dont-email.me>

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>> Because i needed something like ptr = &*vec.end() and MSVC has iterator
>> -debugging by default I had a little header which I included before all
>> other headers.
>>
>> #pragma once
>> #if defined(_MSC_VER)
>>      #if defined(_HAS_ITERATOR_DEBUGGING) && _HAS_ITERATOR_DEBUGGING != 0
>>          #error _HAS_ITERATOR_DEBUGGING must be set to 0
>>      #elif !defined(_HAS_ITERATOR_DEBUGGING)
>>          #define _HAS_ITERATOR_DEBUGGING 0
>>      #endif
>> #endif

> Hm. If you've defined the macro as anything but 0, then this code errs 
> out. Otherwise it defines the macro as 0. So what does it tell you other 
> than that it's Visual C++, which `_MSC_VER` already tells you?

I want to set _HAS_ITERATOR_DEBUGGING to 0 and if it is already set the
compilation should stop.

>> But now I found that to_address( it ) of C++ 20 translates to
>> it.operator ->(), so I don't use the above header any more but
>> just it.operator ->() to stick with C++17 - although the latest
>> MSVC++-upddate is C++20 feature-complete and I could use to_address().

> This seems unrelated to above, perhaps you inadvertently failed to 
> include some more code?

No, if I do ptr = &*vec.end(), depending on _HAS_ITERATOR_DEBUGGING,
the dereferencing of end is runtime-checked and an assertion fails.

> Anyway, it's practically safe to take the address of `*s.end()` for
> a  `std::string`, because since C++11 the buffer has a guaranteed 
> null-terminator, and (at least as I see it) only a perverse 
> implementation would not let `*s.end()` be that final null item.

Interesting, but I'm concerned about vecors in this case.

> But in general, e.g. for a `std::vector`, there is no guaranteed item 
> beyond the last one "in" the collection, so that the `collection.end()` 
> iterator can even be a nullvalue itself. To get a pointer beyond the 
> collection use `collection.data() + collection.size()`.

"ptr = vec.end().operator ->()" works perfectly - and even around
_HAS_ITERATOR_DEBUGGING.

Thread

A way around _HAS_ITERATOR_DEBUGGING Bonita Montero <Bonita.Montero@gmail.com> - 2021-06-02 14:49 +0200
  Re: A way around _HAS_ITERATOR_DEBUGGING "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2021-06-02 15:07 +0200
    Re: A way around _HAS_ITERATOR_DEBUGGING Bonita Montero <Bonita.Montero@gmail.com> - 2021-06-02 15:12 +0200
      Re: A way around _HAS_ITERATOR_DEBUGGING "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2021-06-02 20:27 +0200
        Re: A way around _HAS_ITERATOR_DEBUGGING red floyd <myob@its.invalid> - 2021-06-02 14:24 -0700
        Re: A way around _HAS_ITERATOR_DEBUGGING Bonita Montero <Bonita.Montero@gmail.com> - 2021-06-03 00:54 +0200
        Re: A way around _HAS_ITERATOR_DEBUGGING Öö Tiib <ootiib@hot.ee> - 2021-06-02 17:30 -0700
  Re: A way around _HAS_ITERATOR_DEBUGGING Paavo Helde <myfirstname@osa.pri.ee> - 2021-06-02 16:46 +0300
    Re: A way around _HAS_ITERATOR_DEBUGGING Bonita Montero <Bonita.Montero@gmail.com> - 2021-06-02 16:23 +0200
      Re: A way around _HAS_ITERATOR_DEBUGGING Paavo Helde <myfirstname@osa.pri.ee> - 2021-06-02 19:43 +0300
        Re: A way around _HAS_ITERATOR_DEBUGGING Bonita Montero <Bonita.Montero@gmail.com> - 2021-06-02 18:57 +0200
          Re: A way around _HAS_ITERATOR_DEBUGGING Paavo Helde <myfirstname@osa.pri.ee> - 2021-06-02 21:13 +0300
            Re: A way around _HAS_ITERATOR_DEBUGGING James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-06-02 17:23 -0400
              Re: A way around _HAS_ITERATOR_DEBUGGING Bonita Montero <Bonita.Montero@gmail.com> - 2021-06-03 00:53 +0200
            Re: A way around _HAS_ITERATOR_DEBUGGING Bonita Montero <Bonita.Montero@gmail.com> - 2021-06-03 00:52 +0200
        Re: A way around _HAS_ITERATOR_DEBUGGING Bonita Montero <Bonita.Montero@gmail.com> - 2021-06-02 18:59 +0200
      Re: A way around _HAS_ITERATOR_DEBUGGING Juha Nieminen <nospam@thanks.invalid> - 2021-06-03 09:21 +0000
        Re: A way around _HAS_ITERATOR_DEBUGGING Bonita Montero <Bonita.Montero@gmail.com> - 2021-06-03 11:33 +0200
          Re: A way around _HAS_ITERATOR_DEBUGGING Bo Persson <bo@bo-persson.se> - 2021-06-03 12:17 +0200
            Re: A way around _HAS_ITERATOR_DEBUGGING Bonita Montero <Bonita.Montero@gmail.com> - 2021-06-03 12:25 +0200
          Re: A way around _HAS_ITERATOR_DEBUGGING Juha Nieminen <nospam@thanks.invalid> - 2021-06-03 17:49 +0000
            Re: A way around _HAS_ITERATOR_DEBUGGING MrSpook_ujp@3p26kggzpvpn2h.gov.uk - 2021-06-04 07:43 +0000
        Re: A way around _HAS_ITERATOR_DEBUGGING James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-06-03 11:06 -0400
          Re: A way around _HAS_ITERATOR_DEBUGGING David Brown <david.brown@hesbynett.no> - 2021-06-03 19:07 +0200
          Re: A way around _HAS_ITERATOR_DEBUGGING Paavo Helde <myfirstname@osa.pri.ee> - 2021-06-03 20:18 +0300
            Re: A way around _HAS_ITERATOR_DEBUGGING Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2021-06-04 10:22 +0100
              Re: A way around _HAS_ITERATOR_DEBUGGING Paavo Helde <myfirstname@osa.pri.ee> - 2021-06-04 14:19 +0300
                Re: A way around _HAS_ITERATOR_DEBUGGING Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2021-06-04 13:07 +0100
            Re: A way around _HAS_ITERATOR_DEBUGGING James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-06-04 10:40 -0400
              Re: A way around _HAS_ITERATOR_DEBUGGING Paavo Helde <myfirstname@osa.pri.ee> - 2021-06-04 19:28 +0300
                Re: A way around _HAS_ITERATOR_DEBUGGING James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-06-04 13:04 -0400
                Re: A way around _HAS_ITERATOR_DEBUGGING "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-06-04 13:30 -0700
                Re: A way around _HAS_ITERATOR_DEBUGGING MrSpook_6qpp@dggw8.org - 2021-06-05 09:28 +0000
                Re: A way around _HAS_ITERATOR_DEBUGGING Paavo Helde <myfirstname@osa.pri.ee> - 2021-06-04 23:45 +0300
          Re: A way around _HAS_ITERATOR_DEBUGGING Juha Nieminen <nospam@thanks.invalid> - 2021-06-03 17:52 +0000

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