Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #129470

Re: lvalue types

From scott@slp53.sl.home (Scott Lurndal)
Subject Re: lvalue types
Newsgroups comp.lang.c
References (4 earlier) <ln1sfcl2zj.fsf@kst-u.example.com> <3e0e19ef-eac4-4528-9882-0bd18a18f39f@googlegroups.com> <04a0e8eb-f865-49fd-89fa-9274a1e5c9ac@googlegroups.com> <53a99d45-70aa-4242-b88b-9214770efc88@googlegroups.com> <6aec536c-6547-4615-aa38-b1b873acf6df@googlegroups.com>
Message-ID <Ry7CC.2305$pg3.1653@fx29.iad> (permalink)
Organization UsenetServer - www.usenetserver.com
Date 2018-04-19 21:08 +0000

Show all headers | View raw

supercat@casperkitty.com writes:
>On Thursday, April 19, 2018 at 2:52:08 PM UTC-5, james...@verizon.net wrote:
>> On Thursday, April 19, 2018 at 3:17:27 PM UTC-4, supe...@casperkitty.com wrote:
>> > Are you starting to see, though, why I believe the authors of gcc would
>> > oppose having the Standard say that use of a derived pointer counts as use
>> > of the original for purposes of 6.5p7?
>> 
>> Not really. When I wrote that, I shared their opinion of the likely
>> impact; but I now believe that's based upon a misconception about the
>> scope of that rule. Correcting that misconception should, ideally, be
>> sufficient to remove their opposition.
>
>The authors of gcc have long maintained that code which is incompatible
>with -fstrict-aliasing is "broken".  Making any significant effort to
>notice places where lvalues of one type are used to derive lvalues of
>another would make gcc compatible with most of code that the authors
>of gcc have claimed for over a decade was "broken" and could only be
>supported by gutting optimizations.

Again you impute motive to the gcc team without citation.  In fact,
it's a highly diverse team of volunteer skilled compiler experts.

If one does write such code, which even you must agree is exceedingly
rare, one is free to specify -fno-strict-aliasing on the command
line (with the desired optimization level still specified via -Ox).

I don't see a problem with that, in fact bare-metal, OS and hypervisor code
compiled with gcc typically specifies -fno-strict-aliasing.

Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

lvalue types supercat@casperkitty.com - 2018-03-01 16:38 -0800
  Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-01 17:17 -0800
  Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-03-01 17:37 -0800
    Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-01 22:00 -0800
    Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-01 23:49 -0800
      Re: lvalue types asetofsymbols@gmail.com - 2018-03-05 06:56 -0800
    Re: lvalue types supercat@casperkitty.com - 2018-03-02 00:22 -0800
      Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-02 01:23 -0800
      Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-02 05:04 -0800
        Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-02 06:06 -0800
          Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-02 08:12 -0800
      Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-03-02 09:50 -0800
        Re: lvalue types supercat@casperkitty.com - 2018-03-02 11:33 -0800
          Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-03-02 11:45 -0800
            Re: lvalue types supercat@casperkitty.com - 2018-03-02 16:28 -0800
              Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-03-02 16:54 -0800
                Re: lvalue types supercat@casperkitty.com - 2018-03-02 17:50 -0800
                Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-03-02 19:43 -0800
                Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-02 22:51 -0800
                Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-02 23:07 -0800
                Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-03 01:44 -0800
                Re: lvalue types supercat@casperkitty.com - 2018-03-03 13:01 -0800
          Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-02 22:21 -0800
    Re: lvalue types supercat@casperkitty.com - 2018-03-02 09:24 -0800
    Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-03 00:58 -0800
      Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-03 01:13 -0800
      Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-03-03 13:01 -0800
        Re: lvalue types supercat <flatfinger@casperkitty.com> - 2018-03-03 17:43 -0800
        Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-04 02:22 -0800
          Re: lvalue types supercat@casperkitty.com - 2018-03-04 13:03 -0800
          Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-03-04 13:03 -0800
            Re: lvalue types bartc <bc@freeuk.com> - 2018-03-04 22:32 +0000
            Re: lvalue types supercat@casperkitty.com - 2018-03-05 09:45 -0800
            Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-19 09:54 -0700
              Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-03-19 11:52 -0700
                Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-26 23:44 -0700
                Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-03-27 09:14 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-03-27 12:21 -0700
                Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-28 17:01 -0700
                Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-29 01:54 -0700
                Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-30 08:32 -0700
                Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-03-30 09:25 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-03-30 10:58 -0700
                Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-31 00:52 -0700
                Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-04-02 15:19 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-03 10:06 -0700
                Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-04-03 11:33 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-03 12:19 -0700
                Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-04-03 12:48 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-05 10:17 -0700
                Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-04-05 10:52 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-05 12:39 -0700
                Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-04-06 06:13 -0700
                Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-04-04 16:38 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-03-27 12:09 -0700
                Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-28 10:48 -0700
              Re: lvalue types supercat@casperkitty.com - 2018-03-19 12:27 -0700
          Re: lvalue types jameskuyper@verizon.net - 2018-04-03 14:02 -0700
            Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-04-04 17:32 -0700
              Re: lvalue types jameskuyper@verizon.net - 2018-04-04 20:24 -0700
                Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-04-09 08:31 -0700
                Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-04-11 11:19 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-11 12:44 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-04-12 06:45 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-12 07:54 -0700
                Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-04-12 14:26 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-12 14:43 -0700
                Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-04-12 17:40 -0700
                Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-04-13 03:02 -0700
                Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-04-13 00:27 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-04-13 07:19 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-16 08:52 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-04-16 10:28 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-16 13:58 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-04-16 14:52 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-16 16:22 -0700
                Re: lvalue types Richard Damon <Richard@Damon-Family.org> - 2018-04-16 21:51 -0400
                Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-04-16 19:42 -0700
                Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-04-16 21:30 -0700
                Re: lvalue types Richard Damon <Richard@Damon-Family.org> - 2018-04-17 07:01 -0400
                Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-04-17 04:22 -0700
                Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-04-19 02:43 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-17 07:25 -0700
                Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-04-17 08:48 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-17 09:54 -0700
                Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-04-17 10:37 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-17 11:00 -0700
                Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-04-17 11:48 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-17 12:45 -0700
                Re: lvalue types scott@slp53.sl.home (Scott Lurndal) - 2018-04-17 19:55 +0000
                Re: lvalue types jameskuyper@verizon.net - 2018-04-17 13:13 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-17 14:00 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-04-17 19:45 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-18 08:27 -0700
                Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-04-18 09:12 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-18 10:13 -0700
                Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-04-18 11:01 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-04-18 11:51 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-18 12:15 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-04-18 12:30 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-18 13:25 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-04-19 10:51 -0700
                Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-04-18 12:38 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-18 14:39 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-04-18 21:17 -0700
                Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-04-19 02:40 -0700
                Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-04-19 03:01 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-04-19 06:49 -0700
                Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-04-19 07:58 -0700
                Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-04-20 08:19 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-19 12:17 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-04-19 12:51 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-19 13:37 -0700
                Re: lvalue types scott@slp53.sl.home (Scott Lurndal) - 2018-04-19 21:08 +0000
                Re: lvalue types supercat@casperkitty.com - 2018-04-19 14:50 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-04-19 14:56 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-19 16:13 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-21 10:27 -0700
                Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-04-23 11:37 -0700
                Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-04-18 16:07 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-04-18 09:20 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-18 11:25 -0700
                Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-04-17 14:13 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-17 15:05 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-04-17 19:57 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-18 08:43 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-04-18 09:36 -0700
                Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-04-17 11:37 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-04-17 20:23 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-18 09:23 -0700
                Re: lvalue types scott@slp53.sl.home (Scott Lurndal) - 2018-04-18 17:29 +0000
                Re: lvalue types supercat@casperkitty.com - 2018-04-18 10:47 -0700
                Re: lvalue types bartc <bc@freeuk.com> - 2018-04-18 20:04 +0100
                Re: lvalue types jameskuyper@verizon.net - 2018-04-18 10:48 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-18 13:23 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-04-18 14:26 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-18 15:36 -0700
                Re: lvalue types jameskuyper@verizon.net - 2018-04-19 10:39 -0700
                Re: lvalue types supercat@casperkitty.com - 2018-04-19 12:42 -0700
                Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-04-16 21:29 -0700
                Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-04-23 11:39 -0700
                Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-06-14 02:53 -0700
              Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-04-04 21:30 -0700
      Re: lvalue types supercat@casperkitty.com - 2018-03-03 14:19 -0800
  Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-01 18:03 -0800
  Re: lvalue types John Bode <jfbode1029@gmail.com> - 2018-03-21 10:33 -0700
    Re: lvalue types Keith Thompson <kst-u@mib.org> - 2018-03-21 11:53 -0700
      Re: lvalue types Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-22 00:11 -0700
    Re: lvalue types supercat@casperkitty.com - 2018-03-21 11:53 -0700
    Re: lvalue types Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-26 23:04 -0700

csiph-web