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Groups > comp.lang.c++ > #72757
| From | Paavo Helde <myfirstname@osa.pri.ee> |
|---|---|
| Newsgroups | comp.lang.c++ |
| Subject | Re: two's complement idea |
| Date | 2020-04-02 20:03 +0300 |
| Organization | A noiseless patient Spider |
| Message-ID | <r655s9$7oj$1@dont-email.me> (permalink) |
| References | (14 earlier) <86r1zlgpyx.fsf@linuxsc.com> <r0mn3f$gml$1@dont-email.me> <865zg7hpux.fsf@linuxsc.com> <r3t10p$mt3$1@dont-email.me> <86mu7u6kzx.fsf@linuxsc.com> |
On 2.04.2020 17:05, Tim Rentsch wrote:
> Paavo Helde <myfirstname@osa.pri.ee> writes:
>
>> On 15.02.2020 16:44, Tim Rentsch wrote:
>>
>>> Paavo Helde <myfirstname@osa.pri.ee> writes:
>>>
>>>> On 27.01.2020 12:20, Tim Rentsch wrote:
>>>>
>>>>> Paavo Helde <myfirstname@osa.pri.ee> writes:
>>>>>
>>>>>> On 25.01.2020 16:58, Bart wrote:
>>>>>>
>>>>>>> How would C++ help here, to avoid either that extra logic, or
>>>>>>> the use of that goto? Here's the current outline (for_each_pwq
>>>>>>> is a macro expanding to a regular for-header):
>>>>>>>
>>>>>>> L:
>>>>>>> A;
>>>>>>> for (...) {
>>>>>>> B;
>>>>>>> if (C) continue;
>>>>>>> D;
>>>>>>> goto L;
>>>>>>> }
>
> [...]
>
>>>> BTW, in my own code I have several times encountered similar awkward
>>>> "backward goto" scenarios needed only for unlocking a mutex. And the
>>>> result has always been a mess I'm afraid.
>>>
>>> That's interesting. Is that always because of pending destructor
>>> behavior? If it is, that suggests that the RAII pattern using
>>> standard constructor/destructor semantics has some shortcomings,
>>> which may indicate a need for other behavior choices. For example,
>>> the funky() function above could be writeable using a new 'creturn'
>>> construct, written as
>>>
>>> creturn funky();
>>>
>>> where 'creturn' means first run any pending destructors, and only
>>> after they finish execute the (implied) return statement.
>>
>> This would mess up the lifetime rules of automatic variables, meaning
>> that their lifetime would not match the visual scope any more. I'm
>> sure this would do more harm than good.
>>
>> Also, such 'creturn' would not solve the initial problems, at least
>> not in cases I have had. Effectively, what is needed is to release a
>> mutex lock temporarily in some circumstances, do something out of the
>> mutex lock, then enter the lock again. Logically this is a task for a
>> single function, any 'return' or 'creturn' would split this task into
>> two functions, which is a bit convoluted, which I think you already
>> mentioned above.
>>
>>
>>> Doing
>>> that avoids all the nested locking problems, and also makes the
>>> apparent "tail call" be a true tail call, and so could be optimized
>>> to reuse the stack frame. What other kinds of constructs might make
>>> your troublesome mutex uses more tractable?
>>
>> What would help in my case would be a command like 'retry' or
>> restart' which would destroy all automatic variables in the function
>> and restart the function again. It would be equivalent to a 'goto' to
>> a label in the start of the function, [...]
>
> It is rather amusing that you didn't like creturn, and then
> describe a construct that behaves just the way a creturn would,
> except the retry/restart construct is less general than creturn.
That's because the main problem with the current solution (goto) is that
it is too general. That's the reason why more restricted statements
(break and continue) exist even though they could be replaced by goto-s.
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Re: two's complement idea Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-11-28 12:19 -0800
Re: two's complement idea "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-11-29 00:14 +0100
Re: two's complement idea David Brown <david.brown@hesbynett.no> - 2019-11-29 09:15 +0100
Re: two's complement idea Bo Persson <bo@bo-persson.se> - 2019-11-29 10:58 +0100
Re: two's complement idea David Brown <david.brown@hesbynett.no> - 2019-11-29 12:49 +0100
Re: two's complement idea Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-12-07 07:53 -0800
Re: two's complement idea Öö Tiib <ootiib@hot.ee> - 2019-12-07 08:22 -0800
Re: two's complement idea Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-01-10 20:44 -0800
Re: two's complement idea Öö Tiib <ootiib@hot.ee> - 2020-01-10 23:44 -0800
Re: two's complement idea Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-01-14 07:08 -0800
Re: two's complement idea Öö Tiib <ootiib@hot.ee> - 2020-01-14 08:42 -0800
Re: two's complement idea Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-01-21 02:09 -0800
Re: two's complement idea James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-01-21 05:14 -0800
Re: two's complement idea Daniel <danielaparker@gmail.com> - 2020-01-21 13:08 -0800
Re: two's complement idea James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-01-22 00:07 -0500
Re: two's complement idea Öö Tiib <ootiib@hot.ee> - 2020-01-21 23:21 -0800
Re: two's complement idea Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-01-22 01:51 -0800
Re: two's complement idea David Brown <david.brown@hesbynett.no> - 2020-01-22 11:28 +0100
Re: two's complement idea Bonita Montero <Bonita.Montero@gmail.com> - 2020-01-22 11:52 +0100
Re: two's complement idea Öö Tiib <ootiib@hot.ee> - 2020-01-22 04:47 -0800
Re: two's complement idea Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-04-02 07:19 -0700
Re: two's complement idea James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-02 08:07 -0700
Re: two's complement idea boltar@nowhere.org - 2020-01-21 16:44 +0000
Re: two's complement idea Jorgen Grahn <grahn+nntp@snipabacken.se> - 2020-01-21 20:01 +0000
Re: two's complement idea boltar@nowhere.org - 2020-01-22 11:26 +0000
Re: two's complement idea Christian Gollwitzer <auriocus@gmx.de> - 2020-01-22 20:04 +0100
Re: two's complement idea Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-01-22 11:30 -0800
Re: two's complement idea Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2020-01-22 19:57 +0000
Re: two's complement idea Ian Collins <ian-news@hotmail.com> - 2020-01-23 10:03 +1300
Re: two's complement idea boltar@nowhere.org - 2020-01-23 09:24 +0000
Re: two's complement idea Ian Collins <ian-news@hotmail.com> - 2020-01-24 07:29 +1300
Re: two's complement idea Ian Collins <ian-news@hotmail.com> - 2020-01-23 10:03 +1300
Re: two's complement idea "Fred. Zwarts" <F.Zwarts@KVI.nl> - 2020-01-23 10:09 +0100
Re: two's complement idea boltar@nowhere.org - 2020-01-23 09:29 +0000
Re: two's complement idea Bart <bc@freeuk.com> - 2020-01-24 01:08 +0000
Re: two's complement idea boltar@nowhere.org - 2020-01-24 12:27 +0000
Re: two's complement idea Bart <bc@freeuk.com> - 2020-01-24 01:06 +0000
Re: two's complement idea Bo Persson <bo@bo-persson.se> - 2020-01-24 10:07 +0100
Re: two's complement idea Paavo Helde <myfirstname@osa.pri.ee> - 2020-01-24 11:36 +0200
Re: two's complement idea Öö Tiib <ootiib@hot.ee> - 2020-01-24 17:34 -0800
Re: two's complement idea Siri Cruise <chine.bleu@yahoo.com> - 2020-01-24 17:57 -0800
Re: two's complement idea Bart <bc@freeuk.com> - 2020-01-24 12:19 +0000
Re: two's complement idea Bo Persson <bo@bo-persson.se> - 2020-01-24 14:19 +0100
Re: two's complement idea Bart <bc@freeuk.com> - 2020-01-24 14:11 +0000
Re: two's complement idea Jorgen Grahn <grahn+nntp@snipabacken.se> - 2020-01-24 17:26 +0000
Re: two's complement idea Bart <bc@freeuk.com> - 2020-01-24 17:35 +0000
Re: two's complement idea Paavo Helde <myfirstname@osa.pri.ee> - 2020-01-24 22:27 +0200
Re: two's complement idea James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-01-24 23:21 -0500
Re: two's complement idea Ian Collins <ian-news@hotmail.com> - 2020-01-25 11:06 +1300
Re: two's complement idea Jorgen Grahn <grahn+nntp@snipabacken.se> - 2020-01-24 22:12 +0000
Re: two's complement idea James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-01-24 23:24 -0500
Re: two's complement idea Jorgen Grahn <grahn+nntp@snipabacken.se> - 2020-01-25 09:04 +0000
Re: two's complement idea Öö Tiib <ootiib@hot.ee> - 2020-01-25 04:15 -0800
Re: two's complement idea David Brown <david.brown@hesbynett.no> - 2020-01-25 19:55 +0100
Re: two's complement idea David Brown <david.brown@hesbynett.no> - 2020-01-25 00:05 +0100
Re: two's complement idea Bart <bc@freeuk.com> - 2020-01-25 01:19 +0000
Re: two's complement idea Ian Collins <ian-news@hotmail.com> - 2020-01-25 19:50 +1300
Re: two's complement idea Bart <bc@freeuk.com> - 2020-01-25 11:57 +0000
Re: two's complement idea Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2020-01-25 13:42 +0000
Re: two's complement idea Bart <bc@freeuk.com> - 2020-01-25 14:58 +0000
Re: two's complement idea Ian Collins <ian-news@hotmail.com> - 2020-01-26 07:58 +1300
Re: two's complement idea David Brown <david.brown@hesbynett.no> - 2020-01-25 20:34 +0100
Re: two's complement idea Öö Tiib <ootiib@hot.ee> - 2020-01-25 12:41 -0800
Re: two's complement idea Paavo Helde <myfirstname@osa.pri.ee> - 2020-01-26 16:08 +0200
Re: two's complement idea Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-01-27 02:20 -0800
Re: two's complement idea Paavo Helde <myfirstname@osa.pri.ee> - 2020-01-27 15:03 +0200
Re: two's complement idea Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-02-15 06:44 -0800
Re: two's complement idea Paavo Helde <myfirstname@osa.pri.ee> - 2020-03-06 10:18 +0200
Re: two's complement idea Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-04-02 07:05 -0700
Re: two's complement idea Paavo Helde <myfirstname@osa.pri.ee> - 2020-04-02 20:03 +0300
Re: two's complement idea Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-04-04 12:37 -0700
Re: two's complement idea Ian Collins <ian-news@hotmail.com> - 2020-01-26 07:45 +1300
Re: two's complement idea Bart <bc@freeuk.com> - 2020-01-25 19:56 +0000
Re: two's complement idea Ian Collins <ian-news@hotmail.com> - 2020-01-26 09:49 +1300
Re: two's complement idea Bart <bc@freeuk.com> - 2020-01-25 21:33 +0000
Re: two's complement idea Ian Collins <ian-news@hotmail.com> - 2020-01-26 11:00 +1300
Re: two's complement idea Bart <bc@freeuk.com> - 2020-01-25 22:23 +0000
Re: two's complement idea Ian Collins <ian-news@hotmail.com> - 2020-01-26 11:46 +1300
Re: two's complement idea Paavo Helde <myfirstname@osa.pri.ee> - 2020-01-26 10:55 +0200
Re: two's complement idea Öö Tiib <ootiib@hot.ee> - 2020-01-26 03:47 -0800
Re: two's complement idea Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-01-27 01:28 -0800
Re: two's complement idea Jorgen Grahn <grahn+nntp@snipabacken.se> - 2020-01-25 22:22 +0000
Re: two's complement idea James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-01-25 18:24 -0500
Re: two's complement idea David Brown <david.brown@hesbynett.no> - 2020-01-26 12:54 +0100
Re: two's complement idea Bart <bc@freeuk.com> - 2020-01-26 12:44 +0000
Re: two's complement idea David Brown <david.brown@hesbynett.no> - 2020-01-26 14:58 +0100
Re: two's complement idea Bart <bc@freeuk.com> - 2020-01-26 14:53 +0000
Re: two's complement idea David Brown <david.brown@hesbynett.no> - 2020-01-26 19:10 +0100
Re: two's complement idea Robert Wessel <robertwessel2@yahoo.com> - 2020-01-26 13:20 -0600
Re: two's complement idea Bart <bc@freeuk.com> - 2020-01-26 20:51 +0000
Re: two's complement idea Robert Wessel <robertwessel2@yahoo.com> - 2020-01-26 21:02 -0600
Re: two's complement idea Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-01-26 19:06 -0800
Re: two's complement idea Bart <bc@freeuk.com> - 2020-01-27 18:50 +0000
Re: two's complement idea Robert Wessel <robertwessel2@yahoo.com> - 2020-01-27 14:18 -0600
Re: two's complement idea David Brown <david.brown@hesbynett.no> - 2020-01-27 22:13 +0100
Re: two's complement idea Bart <bc@freeuk.com> - 2020-01-27 21:38 +0000
Re: two's complement idea Robert Wessel <robertwessel2@yahoo.com> - 2020-01-27 19:37 -0600
Re: two's complement idea Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-01-27 19:15 -0800
Re: two's complement idea "Fred. Zwarts" <F.Zwarts@KVI.nl> - 2020-01-28 11:45 +0100
Re: two's complement idea Ian Collins <ian-news@hotmail.com> - 2020-01-27 16:31 +1300
Re: two's complement idea Manfred <noname@add.invalid> - 2020-01-26 18:50 +0100
Re: two's complement idea Jorgen Grahn <grahn+nntp@snipabacken.se> - 2020-01-26 18:57 +0000
Re: two's complement idea David Brown <david.brown@hesbynett.no> - 2020-01-26 20:46 +0100
Re: two's complement idea Robert Wessel <robertwessel2@yahoo.com> - 2020-01-26 13:14 -0600
Re: two's complement idea David Brown <david.brown@hesbynett.no> - 2020-01-26 22:15 +0100
Re: two's complement idea Robert Wessel <robertwessel2@yahoo.com> - 2020-01-27 21:06 -0600
Re: two's complement idea David Brown <david.brown@hesbynett.no> - 2020-01-28 13:08 +0100
Re: two's complement idea Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-01-27 01:50 -0800
Re: two's complement idea Ian Collins <ian-news@hotmail.com> - 2020-01-27 08:21 +1300
Re: two's complement idea David Brown <david.brown@hesbynett.no> - 2020-01-25 20:14 +0100
Re: two's complement idea David Brown <david.brown@hesbynett.no> - 2020-01-25 20:12 +0100
Re: two's complement idea Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-01-27 07:48 -0800
Re: two's complement idea Bonita Montero <Bonita.Montero@gmail.com> - 2020-02-18 18:46 +0100
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