Digest for comp.lang.c++@googlegroups.com - 6 updates in 3 topics

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• Why should a "c" programmer learn c++ ? - 4 Updates
• Why should a "c" programmer learn c++ ? (V2) - 1 Update
• problem with std::string::c_str() - 1 Update

Why should a "c" programmer learn c++ ?

Chris Vine <chris@cvine--nospam--.freeserve.co.uk>: Sep 11 07:58PM +0100 On Fri, 11 Sep 2020 17:28:51 +0200 > different from the behaviour in C.   > (I'm not saying you are wrong here - but you might be, and I think we > both hope that you /are/ wrong.)   Compare N4849 and C++17. This is either a very last minute change to the draft standard before it was put to international ballot, or it represents the inclusion of a defect report not in the actual balloted standard. This is clearly in response to http://wg21.link/p0593r6 (it incorporates the proposed wording in that document), which pointed out the considerable deficiencies in C++17 and in the then draft standard respecting trivial objects. P0593r6 indicates that its proposals were too late to make the cut for C++20. Maybe the then draft standard N4849 was thought to be so defective in the light of the report as to need urgent rule bending. It is good to see nonetheless.   It clearly deals with my first example. It probably deals with my second example (pointer arithmetic) but I would need to consider that further. It obviously doesn't deal with my third point (the rules on pointer interconvertibility and std::launder as an addition to the strict aliasing rules).

David Brown <david.brown@hesbynett.no>: Sep 12 12:03AM +0200 On 11/09/2020 20:57, Chris Vine wrote: > http://wg21.link/p0593r6 , which pointed out the considerable > deficiencies in C++17 and in the then draft standard respecting > trivial objects.   For your convenience (I certainly find it convenient), I found the link from:   <https://en.cppreference.com/w/cpp/links>   This labels N4860 as "C++20 final working draft". I don't know any more details than that.

Chris Vine <chris@cvine--nospam--.freeserve.co.uk>: Sep 11 11:31PM +0100 On Sat, 12 Sep 2020 00:03:50 +0200   > <https://en.cppreference.com/w/cpp/links>   > This labels N4860 as "C++20 final working draft". I don't know any more > details than that.   Given that that document has a ISO copyright notice in respect of which the link appears to be in flagrant breach, that looks a bit dodgy to me. But hey, if you can alter an international treaty what's an ISO publication ...

Richard Damon <Richard@Damon-Family.org>: Sep 11 07:22PM -0400 On 9/11/20 6:31 PM, Chris Vine wrote: > which the link appears to be in flagrant breach, that looks a bit dodgy > to me. But hey, if you can alter an international treaty what's an ISO > publication ...   Since the link goes to iso.org, and you are downloading it from the ISO server, I don't think they can make much of a copyright violation claim for you downloading it.   The COULD go after you, if you did something like try to sell to someone, maybe after small edit to make it look like the actual standard instead of the final draft.   ISO seems to have a policy that the drafts are free, but the published standards are expensive. For most people, the final drafts are good enough, so they can get it for free. For the companies that the difference is important, the price of the Standard isn't that significant.

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Why should a "c" programmer learn c++ ? (V2)

Joe Pfeiffer <pfeiffer@cs.nmsu.edu>: Sep 11 04:20PM -0600 > Important that it needs to be marked as special in some way. It's been > that way since before the Internet boom. I refer you to "What To Do > When the Trisector Comes" by Underwood Dudley.   I hadn't come across that little article before. Thanks, it was fun.

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problem with std::string::c_str()

Cholo Lennon <chololennon@hotmail.com>: Sep 11 06:45PM -0300 On 9/11/20 4:11 PM, RM wrote: > " */ >     const char *cmd = command.c_str(); > /* here problem: cmd == "p" */   What are the values of command[1], command[2], and cmd[2], cmd[3]? (I assume that command[0] == 'p' and cmd[1] == 0). It's weird that c_str truncates the string in that way. Maybe 'command' contains a double byte string...     -- Cholo Lennon Bs.As. ARG

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