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Re: Which exception for a buffer overrun?

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On 16/10/2019 00:13, Scott Lurndal wrote:
> Soviet_Mario <SovietMario@CCCP.MIR> writes:
> 
>> One thing I really can't stand is the way C used to share a
>> single variable (errno) to store status, that may be
>> overwritten unpredictably
> 
> Can you elaborate?   It was well understood and documented when errno could
> be modified (on any system or library call).
> 

I must have mis-expressed. Unpredictably would have meant 
that this variable can be async modified anywhere and 
anytime (and in multithread context, or even in event-driven 
programs, when a routine could be called amidst another call 
is working, and that gets frozen and revived later, one 
might find errno modified even just after tested in the last 
instruction on the "local" flow).

And in that case even knowing in advance this may happen is 
useless practically.
Sure : often this modification is not that relevant locally 
(an error occurred elsewhere is more likely not affect the 
reprise of the code frozen before) but not always.
Consider an error generated on a shared resource, like a 
file/stream and so.
Routine A tests a file (probing errno after some operation) 
before starting to worki and prepares to work on it

then an async event trigger invoke routine B (with A being 
put on wait) which generates an error on the same file, 
setting errno.
When resumed, routine A will assume wrongly that the file is 
not corrupted, but actually is.

Actually even return value test does not seem (to me) to 
protect much from this.
Exception is more resilient, at the cost of speed, as it 
catch on the fly ex-post rather then test-and-act)


-- 
1) Resistere, resistere, resistere.
2) Se tutti pagano le tasse, le tasse le pagano tutti
Soviet_Mario - (aka Gatto_Vizzato)

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Which exception for a buffer overrun? Frederick Gotham <cauldwell.thomas@gmail.com> - 2019-10-15 03:00 -0700
  Re:Which exception for a buffer overrun? melzzzzz <mel@melzzzzz.com> - 2019-10-15 12:52 +0200
    Re: Re:Which exception for a buffer overrun? queequeg@trust.no1 (Queequeg) - 2019-10-16 12:52 +0000
      Re: Re:Which exception for a buffer overrun? melzzzzz <mel@melzzzzz.com> - 2019-10-16 18:29 +0200
  Re: Which exception for a buffer overrun? Paavo Helde <myfirstname@osa.pri.ee> - 2019-10-15 13:54 +0300
    Re: Which exception for a buffer overrun? Frederick Gotham <cauldwell.thomas@gmail.com> - 2019-10-15 04:08 -0700
      Re: Which exception for a buffer overrun? David Brown <david.brown@hesbynett.no> - 2019-10-15 13:57 +0200
        Re: Which exception for a buffer overrun? Soviet_Mario <SovietMario@CCCP.MIR> - 2019-10-15 23:59 +0200
          Re: Which exception for a buffer overrun? scott@slp53.sl.home (Scott Lurndal) - 2019-10-15 22:13 +0000
            Re: Which exception for a buffer overrun? Soviet_Mario <SovietMario@CCCP.MIR> - 2019-10-16 15:04 +0200
          Re: Which exception for a buffer overrun? Paavo Helde <myfirstname@osa.pri.ee> - 2019-10-16 07:57 +0300
            Re: Which exception for a buffer overrun? Soviet_Mario <SovietMario@CCCP.MIR> - 2019-10-16 15:05 +0200
            Re: Which exception for a buffer overrun? Keith Thompson <kst-u@mib.org> - 2019-10-16 15:34 -0700
          Re: Which exception for a buffer overrun? David Brown <david.brown@hesbynett.no> - 2019-10-16 10:16 +0200
            Re: Which exception for a buffer overrun? Öö Tiib <ootiib@hot.ee> - 2019-10-16 05:54 -0700
              Re: Which exception for a buffer overrun? David Brown <david.brown@hesbynett.no> - 2019-10-16 16:12 +0200
                Re: Which exception for a buffer overrun? Soviet_Mario <SovietMario@CCCP.MIR> - 2019-10-16 20:45 +0200
                Re: Which exception for a buffer overrun? Öö Tiib <ootiib@hot.ee> - 2019-10-17 06:34 -0700
                Re: Which exception for a buffer overrun? David Brown <david.brown@hesbynett.no> - 2019-10-17 16:34 +0200
            Re: Which exception for a buffer overrun? Ian Collins <ian-news@hotmail.com> - 2019-10-17 08:15 +1300
              Re: Which exception for a buffer overrun? David Brown <david.brown@hesbynett.no> - 2019-10-16 23:00 +0200
                Re: Which exception for a buffer overrun? Ian Collins <ian-news@hotmail.com> - 2019-10-17 10:36 +1300
                Re: Which exception for a buffer overrun? David Brown <david.brown@hesbynett.no> - 2019-10-17 10:14 +0200
                Re: Which exception for a buffer overrun? Daniel <danielaparker@gmail.com> - 2019-10-16 20:06 -0700
            Re: Which exception for a buffer overrun? Bonita Montero <Bonita.Montero@gmail.com> - 2019-10-18 09:45 +0200
        Re: Which exception for a buffer overrun? Bonita Montero <Bonita.Montero@gmail.com> - 2019-10-17 21:22 +0200
      Re: Which exception for a buffer overrun? Paavo Helde <myfirstname@osa.pri.ee> - 2019-10-15 17:48 +0300
    Re: Which exception for a buffer overrun? "Fred. Zwarts" <F.Zwarts@KVI.nl> - 2019-10-15 13:09 +0200
      Re: Which exception for a buffer overrun? David Brown <david.brown@hesbynett.no> - 2019-10-15 13:35 +0200
        Re: Which exception for a buffer overrun? scott@slp53.sl.home (Scott Lurndal) - 2019-10-15 13:30 +0000
      Re: Which exception for a buffer overrun? melzzzzz <mel@melzzzzz.com> - 2019-10-15 13:49 +0200
        Re: Which exception for a buffer overrun? David Brown <david.brown@hesbynett.no> - 2019-10-15 13:59 +0200
      Re: Which exception for a buffer overrun? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-10-15 14:48 +0000
        Re: Which exception for a buffer overrun? Paavo Helde <myfirstname@osa.pri.ee> - 2019-10-15 18:37 +0300
          Re: Which exception for a buffer overrun? melzzzzz <mel@melzzzzz.com> - 2019-10-15 18:48 +0200
      Re: Which exception for a buffer overrun? queequeg@trust.no1 (Queequeg) - 2019-10-16 13:00 +0000
    Re: Which exception for a buffer overrun? Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2019-10-15 18:21 +0100
      Re: Which exception for a buffer overrun? Melzzzzz <Melzzzzz@zzzzz.com> - 2019-10-15 20:32 +0000
        Re: Which exception for a buffer overrun? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-10-16 06:20 +0000
    Re: Which exception for a buffer overrun? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-10-16 14:43 -0700
  Re: Which exception for a buffer overrun? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-10-15 11:12 +0000
  Re: Which exception for a buffer overrun? Öö Tiib <ootiib@hot.ee> - 2019-10-15 13:44 -0700
    Re: Which exception for a buffer overrun? Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2019-10-15 22:43 +0100
      Re: Which exception for a buffer overrun? Öö Tiib <ootiib@hot.ee> - 2019-10-16 00:01 -0700
        Re: Which exception for a buffer overrun? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-10-16 19:02 +0000
          Re: Which exception for a buffer overrun? Öö Tiib <ootiib@hot.ee> - 2019-10-16 15:22 -0700
            Re: Which exception for a buffer overrun? Mike Terry <news.dead.person.stones@darjeeling.plus.com> - 2019-10-17 03:31 +0100
              Re: Which exception for a buffer overrun? Ian Collins <ian-news@hotmail.com> - 2019-10-17 15:35 +1300
                Re: Which exception for a buffer overrun? David Brown <david.brown@hesbynett.no> - 2019-10-17 10:17 +0200
            Re: Which exception for a buffer overrun? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-10-20 22:18 +0000
              Re: Which exception for a buffer overrun? Öö Tiib <ootiib@hot.ee> - 2019-10-21 04:06 -0700

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