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Re: Can extern "C" functions throw exceptions

From "Alf P. Steinbach" <alf.p.steinbach@gmail.com>
Newsgroups comp.lang.c++
Subject Re: Can extern "C" functions throw exceptions
Date 2021-09-11 17:00 +0200
Organization A noiseless patient Spider
Message-ID <shigaa$rva$1@dont-email.me> (permalink)
References <shi0pt$71u$1@dont-email.me> <shi5g0$9cu$1@dont-email.me> <shib96$j4b$2@dont-email.me>

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On 11 Sep 2021 15:34, Bonita Montero wrote:
> Am 11.09.2021 um 13:55 schrieb Alf P. Steinbach:
>> On 11 Sep 2021 12:35, Bonita Montero wrote:
>>> Is it specified that extern "C" functions never throw exceptions.
>>
>> No, I don't think so, but that's a common and reasonable assumption.
>>
>>
>>> If it is I see a problem with this: if I pass a function-pointer
>>> to a C++-function an extern "C" function and this function is
>>> called through its pointer by the extern "C" function it might
>>> throw an exception.
>>
>> Yes, that can for example happen in Windows desktop programming in a 
>> WM_PAINT handler.
> 
> I'm pretty sure the WndProc handling WM_PAINT can't throw an exception
> because the Windows-APIs calling it don't have any unwind-handlers, i.e.
> linked unrolling with 32 bit code or table-driven unrolled handlers for
> 32 bit code.

You're right that the Windows code calling it lacks unwind-handlers for 
C++ exceptions.

The part you snipped discussed one way to deal with that in C++11 and 
later, because it's the general problem with exceptions in C callbacks 
provided by C++ code.

Note that the WM_PAINT handler is generally C++ app code, and it can 
throw exceptions by design and/or inadvertently. I prefer to deal with 
that. I do know from discussions with some Microsoft programmers (both 
when the Microsoft Usenet servers were still going, via mailing list 
when I was an MSVP in Visual C++ in 2012/13, and later at Reddit and 
elsewhere) that they don't quite understand the need to deal with 
exceptions or how, and that they generally don't understand the utility 
of exceptions in such code, in particular for DirectX where the most 
vocal of them erroneously believe that exceptions can't be used, and 
that they absolutely have to be right about that because everyone they 
know believe the same... But then, these are they guys writing `void 
main` and so on. And these are the guys creating a Windows calculator 
that by default evaluates 2+3*4 as (2+3)*4. And so on. And on. :-o

- Alf

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Thread

Can extern "C" functions throw exceptions Bonita Montero <Bonita.Montero@gmail.com> - 2021-09-11 12:35 +0200
  Re: Can extern "C" functions throw exceptions Bo Persson <bo@bo-persson.se> - 2021-09-11 13:49 +0200
    Re: Can extern "C" functions throw exceptions "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2021-09-11 13:57 +0200
    Re: Can extern "C" functions throw exceptions Paavo Helde <myfirstname@osa.pri.ee> - 2021-09-11 15:19 +0300
    Re: Can extern "C" functions throw exceptions Bonita Montero <Bonita.Montero@gmail.com> - 2021-09-11 15:32 +0200
    Re: Can extern "C" functions throw exceptions HorseyWorsey@the_stables.com - 2021-09-11 15:54 +0000
  Re: Can extern "C" functions throw exceptions "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2021-09-11 13:55 +0200
    Re: Can extern "C" functions throw exceptions Bonita Montero <Bonita.Montero@gmail.com> - 2021-09-11 15:34 +0200
      Re: Can extern "C" functions throw exceptions Bonita Montero <Bonita.Montero@gmail.com> - 2021-09-11 15:58 +0200
      Re: Can extern "C" functions throw exceptions "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2021-09-11 17:00 +0200
        Re: Can extern "C" functions throw exceptions "daniel...@gmail.com" <danielaparker@gmail.com> - 2021-10-06 13:36 -0700
          Re: Can extern "C" functions throw exceptions Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-06 20:42 +0000
            Re: Can extern "C" functions throw exceptions Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-06 16:12 -0700
              Re: Can extern "C" functions throw exceptions Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-06 23:22 +0000
                Re: Can extern "C" functions throw exceptions Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-06 17:03 -0700
    Re: Can extern "C" functions throw exceptions HorseyWorsey@the_stables.com - 2021-09-11 15:56 +0000
    Re: Can extern "C" functions throw exceptions David Brown <david.brown@hesbynett.no> - 2021-09-11 20:10 +0200
      Re: Can extern "C" functions throw exceptions Juha Nieminen <nospam@thanks.invalid> - 2021-09-12 09:20 +0000
        Re: Can extern "C" functions throw exceptions Paavo Helde <myfirstname@osa.pri.ee> - 2021-09-12 12:34 +0300
        Re: Can extern "C" functions throw exceptions David Brown <david.brown@hesbynett.no> - 2021-09-12 12:24 +0200
          Re: Can extern "C" functions throw exceptions Bonita Montero <Bonita.Montero@gmail.com> - 2021-09-12 12:29 +0200
        Re: Can extern "C" functions throw exceptions Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2021-09-12 14:44 +0100
          Re: Can extern "C" functions throw exceptions James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-09-12 23:13 -0400
            Re: Can extern "C" functions throw exceptions David Brown <david.brown@hesbynett.no> - 2021-09-13 09:30 +0200
            Re: Can extern "C" functions throw exceptions Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-06 13:12 -0700
              Re: Can extern "C" functions throw exceptions "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2021-10-07 07:09 -0700
                Re: Can extern "C" functions throw exceptions Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-14 15:21 -0800
                Re: Can extern "C" functions throw exceptions Richard Damon <Richard@Damon-Family.org> - 2021-12-14 21:17 -0500
                Re: Can extern "C" functions throw exceptions Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-16 04:21 -0800
                Re: Can extern "C" functions throw exceptions "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2021-12-14 19:06 -0800
                Re: Can extern "C" functions throw exceptions Ian Collins <ian-news@hotmail.com> - 2021-12-16 13:14 +1300
                Re: Can extern "C" functions throw exceptions "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-12-15 18:05 -0800
                Re: Can extern "C" functions throw exceptions Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-16 04:37 -0800
                Re: Can extern "C" functions throw exceptions Ian Collins <ian-news@hotmail.com> - 2021-12-17 09:39 +1300
                Re: Can extern "C" functions throw exceptions Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-16 19:24 -0800
                Re: Can extern "C" functions throw exceptions Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-16 04:29 -0800
          Re: Can extern "C" functions throw exceptions Juha Nieminen <nospam@thanks.invalid> - 2021-09-13 05:34 +0000
            Re: Can extern "C" functions throw exceptions Paavo Helde <myfirstname@osa.pri.ee> - 2021-09-13 09:55 +0300
  Re: Can extern "C" functions throw exceptions Paavo Helde <myfirstname@osa.pri.ee> - 2021-09-11 15:12 +0300
  Re: Can extern "C" functions throw exceptions red floyd <no.spam.here@its.invalid> - 2021-09-13 13:21 -0700

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