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Re: Why does this work in MSVC 2019...

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On 5/18/2021 9:01 AM, Mike Terry wrote:
> On 18/05/2021 00:05, Chris M. Thomasson wrote:
>> I don't think this should work at all! It should segfault.
>> _______________________________
[...]
>> _______________________________
> 
> Posting around 150 lines of code, then asking "why doesn't this 
> segfault?" with no further explanation isn't good.  It would have been 
> helpful at least have said which bit of code you thought should produce 
> a segfault...

Yeah, sorry about that.


> OK, so I guess your issue is with the two search_id functions, which 
> return a reference to a local result, e.g.:
> 
>  >      set_t::iterator const& search_id(unsigned long id) const
>  >      {
>  >          return m_set.find(id);
>  >      }
> 
> When these are used you expect a segfault, but when I run the code (MSVS 
> 17) there is no seg-fault because the original iterator storage on the 
> stack hasn't been overwritten at that point.  (There is a compile 
> warning "returning address of local variable or temporary".)
> 
> The obvious correct approach would be to just return the iterator by 
> value.  (And I'd wonder why would you want to make it const, but I 
> suppose this is some kind of experiment rather than production code.)

It is a crude quick experiment. I never used is_transparent before. Then 
I noticed that MSVC actually runs the bugged code. I got the warnings as 
well, but still wondered about why it ran to completion.

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Why does this work in MSVC 2019... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-05-17 16:05 -0700
  Re: Why does this work in MSVC 2019... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-05-17 16:11 -0700
    Re: Why does this work in MSVC 2019... Branimir Maksimovic <branimir.maksimovic@gmail.com> - 2021-05-17 23:24 +0000
  Re: Why does this work in MSVC 2019... "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2021-05-18 22:29 +0200
    Re: Why does this work in MSVC 2019... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-05-18 15:09 -0700
      Re: Why does this work in MSVC 2019... Christian Gollwitzer <auriocus@gmx.de> - 2021-05-19 07:57 +0200
        Re: Why does this work in MSVC 2019... James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-05-19 09:58 -0400
  Re: Why does this work in MSVC 2019... Mike Terry <news.dead.person.stones@darjeeling.plus.com> - 2021-05-18 17:01 +0100
    Re: Why does this work in MSVC 2019... Bonita Montero <Bonita.Montero@gmail.com> - 2021-05-18 18:12 +0200
      Re: Why does this work in MSVC 2019... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-05-18 14:50 -0700
        Re: Why does this work in MSVC 2019... Bonita Montero <Bonita.Montero@gmail.com> - 2021-05-19 01:42 +0200
          Re: Why does this work in MSVC 2019... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-05-18 16:48 -0700
            Re: Why does this work in MSVC 2019... Öö Tiib <ootiib@hot.ee> - 2021-05-18 17:55 -0700
              Re: Why does this work in MSVC 2019... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-05-18 20:06 -0700
                Re: Why does this work in MSVC 2019... Paavo Helde <myfirstname@osa.pri.ee> - 2021-05-19 09:50 +0300
                Re: Why does this work in MSVC 2019... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-05-19 00:45 -0700
            Re: Why does this work in MSVC 2019... Bonita Montero <Bonita.Montero@gmail.com> - 2021-05-19 07:02 +0200
              Re: Why does this work in MSVC 2019... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-05-19 00:46 -0700
      Re: Why does this work in MSVC 2019... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-05-18 15:10 -0700
    Re: Why does this work in MSVC 2019... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-05-18 14:59 -0700
  Re: Why does this work in MSVC 2019... Andrey Tarasevich <andreytarasevich@hotmail.com> - 2021-05-20 03:44 +0300
    Re: Why does this work in MSVC 2019... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-05-19 20:38 -0700

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