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Re: Static bounds checking (was Re: C23 (C2x) changes)

From Kaz Kylheku <480-992-1380@kylheku.com>
Newsgroups comp.lang.c
Subject Re: Static bounds checking (was Re: C23 (C2x) changes)
Date 2021-09-25 20:49 +0000
Organization A noiseless patient Spider
Message-ID <20210925134720.515@kylheku.com> (permalink)
References (2 earlier) <ptf3J.44292$ol1.39305@fx42.iad> <sikth7$vpc$1@dont-email.me> <8xu3J.74157$QzOf.42137@fx17.iad> <simk7g$afa$1@dont-email.me> <LLD3J.125618$F26.58164@fx44.iad>

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On 2021-09-25, Branimir Maksimovic <branimir.maksimovic@gmail.com> wrote:
> On 2021-09-25, Bonita Montero <Bonita.Montero@gmail.com> wrote:
>>> Look, bounds checking is costly, if done in run time, and people think that
>>> using to_string is not efficient :P
>>
>> Bounds-checking is only costly when you have random-access array access.
>> If you iterate linearely the loop will be split in three passes by the
>> optimizer: the part before the begin of the array, the part within the
>> array and the part afterwards; that's how Java and Rust do it. And Rust
>> isn't significantly slower than C or c++.
>>
>
> That's costly.
> Fact when iterating over array hides it (because of cache), but not all accesses
> are sequential.

Never mind caching; when you're iterating over an array, you can hoist
the bounds check out of the loop (if you know that the loop has no
termination condition other than the array bounds).

-- 
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal

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C23 (C2x) changes Mehdi Amini <atorrses@gmail.com> - 2021-09-20 10:54 +0430
  Re: C23 (C2x) changes David Brown <david.brown@hesbynett.no> - 2021-09-20 09:35 +0200
    Re: C23 (C2x) changes Mehdi Amini <atorrses@gmail.com> - 2021-09-21 11:01 +0430
  Re: C23 (C2x) changes John Bode <jfbode1029@gmail.com> - 2021-09-20 10:41 -0500
    Re: C23 (C2x) changes David Brown <david.brown@hesbynett.no> - 2021-09-20 18:17 +0200
      Re: C23 (C2x) changes Bart <bc@freeuk.com> - 2021-09-20 18:55 +0100
        Re: C23 (C2x) changes scott@slp53.sl.home (Scott Lurndal) - 2021-09-20 18:21 +0000
        Re: C23 (C2x) changes David Brown <david.brown@hesbynett.no> - 2021-09-20 21:39 +0200
          Re: C23 (C2x) changes Bart <bc@freeuk.com> - 2021-09-20 21:07 +0100
            Re: C23 (C2x) changes David Brown <david.brown@hesbynett.no> - 2021-09-20 22:59 +0200
              Re: C23 (C2x) changes Bart <bc@freeuk.com> - 2021-09-20 22:29 +0100
                Re: C23 (C2x) changes Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-09-20 17:43 -0700
                Re: C23 (C2x) changes David Brown <david.brown@hesbynett.no> - 2021-09-21 17:56 +0200
                Re: C23 (C2x) changes Bart <bc@freeuk.com> - 2021-09-21 18:05 +0100
                Re: C23 (C2x) changes Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-09-21 11:42 -0700
                Re: C23 (C2x) changes David Brown <david.brown@hesbynett.no> - 2021-09-22 11:37 +0200
                Re: C23 (C2x) changes Bart <bc@freeuk.com> - 2021-09-22 11:55 +0100
                Re: C23 (C2x) changes David Brown <david.brown@hesbynett.no> - 2021-09-22 14:21 +0200
                Re: C23 (C2x) changes Bart <bc@freeuk.com> - 2021-09-22 13:58 +0100
                Re: C23 (C2x) changes Ian Pilcher <arequipeno@gmail.com> - 2021-09-22 12:02 -0500
                Re: C23 (C2x) changes scott@slp53.sl.home (Scott Lurndal) - 2021-09-22 17:19 +0000
          Re: C23 (C2x) changes Bart <bc@freeuk.com> - 2021-09-20 23:05 +0100
            Re: C23 (C2x) changes scott@slp53.sl.home (Scott Lurndal) - 2021-09-20 22:47 +0000
              Re: C23 (C2x) changes Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2021-09-20 22:58 +0000
              Re: C23 (C2x) changes Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-02 07:16 -0700
                Re: C23 (C2x) changes Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-02 15:15 +0000
            Re: C23 (C2x) changes Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-09-20 17:45 -0700
        Re: C23 (C2x) changes Manfred <noname@add.invalid> - 2021-09-27 17:15 +0200
          Re: C23 (C2x) changes Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-09-27 17:38 +0100
            Re: C23 (C2x) changes Manfred <noname@add.invalid> - 2021-09-27 23:18 +0200
              Re: C23 (C2x) changes antispam@math.uni.wroc.pl - 2021-09-28 13:53 +0000
              Re: C23 (C2x) changes Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-02 08:07 -0700
                Re: C23 (C2x) changes Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-02 15:18 +0000
                Re: C23 (C2x) changes Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-02 15:04 -0700
                Re: C23 (C2x) changes Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-03 01:58 +0000
                Re: C23 (C2x) changes Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-02 22:06 -0700
                Re: C23 (C2x) changes Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-03 10:43 +0000
                Re: C23 (C2x) changes Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-03 13:30 -0700
                Re: C23 (C2x) changes Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-04 05:04 +0000
                Re: C23 (C2x) changes Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-03 23:24 -0700
                Re: C23 (C2x) changes Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-04 06:54 +0000
                Re: C23 (C2x) changes David Brown <david.brown@hesbynett.no> - 2021-10-04 09:58 +0200
                Re: C23 (C2x) changes Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-04 15:52 +0000
                Re: C23 (C2x) changes Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-04 10:45 -0700
                Re: C23 (C2x) changes Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-04 20:30 +0000
                Re: C23 (C2x) changes Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-06 03:57 -0700
                Re: C23 (C2x) changes Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-06 12:27 +0000
          Re: C23 (C2x) changes Branimir Maksimovic <branimir.maksimovic@gmail.com> - 2021-09-29 03:38 +0000
      Re: C23 (C2x) changes Bart <bc@freeuk.com> - 2021-10-15 11:35 +0100
        Re: C23 (C2x) changes Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2021-10-15 18:27 +0000
          Re: C23 (C2x) changes Bart <bc@freeuk.com> - 2021-10-15 20:08 +0100
          Re: C23 (C2x) changes Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2021-10-15 19:20 +0000
            Re: C23 (C2x) changes Bart <bc@freeuk.com> - 2021-10-15 21:50 +0100
    Re: C23 (C2x) changes Florian Weimer <fw@deneb.enyo.de> - 2021-10-03 09:43 +0200
      Re: C23 (C2x) changes Guillaume <message@bottle.org> - 2021-10-03 18:53 +0200
      Re: C23 (C2x) changes Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-03 13:55 -0700
  Re: C23 (C2x) changes William Ahern <william@25thandClement.com> - 2021-09-21 22:57 -0700
    Re: C23 (C2x) changes Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-02 08:55 -0700
      Re: C23 (C2x) changes Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-02 16:36 +0000
  Re: C23 (C2x) changes Guillaume <message@bottle.org> - 2021-09-22 20:27 +0200
    Re: C23 (C2x) changes Philipp Klaus Krause <pkk@spth.de> - 2021-09-22 22:25 +0200
      Re: C23 (C2x) changes Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-09-22 14:05 -0700
        Re: C23 (C2x) changes Bart <bc@freeuk.com> - 2021-09-22 23:24 +0100
          Re: C23 (C2x) changes Thiago Adams <thiago.adams@gmail.com> - 2021-09-22 18:49 -0700
        Re: C23 (C2x) changes Guillaume <message@bottle.org> - 2021-09-23 18:47 +0200
  Static bounds checking (was Re: C23 (C2x) changes) William Ahern <william@25thandClement.com> - 2021-09-23 21:11 -0700
    Re: Static bounds checking (was Re: C23 (C2x) changes) David Brown <david.brown@hesbynett.no> - 2021-09-24 08:51 +0200
      Re: Static bounds checking (was Re: C23 (C2x) changes) Philipp Klaus Krause <pkk@spth.de> - 2021-09-24 09:30 +0200
    Re: Static bounds checking (was Re: C23 (C2x) changes) Branimir Maksimovic <branimir.maksimovic@gmail.com> - 2021-09-24 07:52 +0000
      Re: Static bounds checking (was Re: C23 (C2x) changes) Philipp Klaus Krause <pkk@spth.de> - 2021-09-24 12:32 +0200
        Re: Static bounds checking (was Re: C23 (C2x) changes) Branimir Maksimovic <branimir.maksimovic@gmail.com> - 2021-09-24 10:49 +0000
          Re: Static bounds checking (was Re: C23 (C2x) changes) Philipp Klaus Krause <pkk@spth.de> - 2021-09-24 14:46 +0200
      Re: Static bounds checking (was Re: C23 (C2x) changes) Bonita Montero <Bonita.Montero@gmail.com> - 2021-09-24 18:14 +0200
        Re: Static bounds checking (was Re: C23 (C2x) changes) Branimir Maksimovic <branimir.maksimovic@gmail.com> - 2021-09-25 01:00 +0000
          Re: Static bounds checking (was Re: C23 (C2x) changes) Philipp Klaus Krause <pkk@spth.de> - 2021-09-25 07:44 +0200
            Re: Static bounds checking (was Re: C23 (C2x) changes) Branimir Maksimovic <branimir.maksimovic@gmail.com> - 2021-09-25 11:28 +0000
            Re: Static bounds checking (was Re: C23 (C2x) changes) antispam@math.uni.wroc.pl - 2021-09-28 10:56 +0000
          Re: Static bounds checking (was Re: C23 (C2x) changes) Bonita Montero <Bonita.Montero@gmail.com> - 2021-09-25 09:48 +0200
            Re: Static bounds checking (was Re: C23 (C2x) changes) Branimir Maksimovic <branimir.maksimovic@gmail.com> - 2021-09-25 11:30 +0000
              Re: Static bounds checking (was Re: C23 (C2x) changes) Kaz Kylheku <480-992-1380@kylheku.com> - 2021-09-25 20:49 +0000
                Re: Static bounds checking (was Re: C23 (C2x) changes) Branimir Maksimovic <branimir.maksimovic@gmail.com> - 2021-09-26 00:04 +0000
              Re: Static bounds checking (was Re: C23 (C2x) changes) Bonita Montero <Bonita.Montero@gmail.com> - 2021-09-26 06:56 +0200
  Re: C23 (C2x) changes Thiago Adams <thiago.adams@gmail.com> - 2021-09-27 10:15 -0700
    Re: C23 (C2x) changes Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-09-27 11:15 -0700
      Re: C23 (C2x) changes David Brown <david.brown@hesbynett.no> - 2021-09-27 22:11 +0200
      Re: C23 (C2x) changes Thiago Adams <thiago.adams@gmail.com> - 2021-09-27 14:20 -0700
        Re: C23 (C2x) changes Thiago Adams <thiago.adams@gmail.com> - 2021-09-27 14:31 -0700
      Re: C23 (C2x) changes Mehdi Amini <atorrses@gmail.com> - 2021-09-28 10:43 +0330
  Re: C23 (C2x) changes Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-06 04:01 -0700
    Re: C23 (C2x) changes Thiago Adams <thiago.adams@gmail.com> - 2021-10-06 04:42 -0700
      Re: C23 (C2x) changes Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-29 04:04 -0700
        Re: C23 (C2x) changes David Brown <david.brown@hesbynett.no> - 2021-10-29 16:34 +0200
    Re: C23 (C2x) changes Guillaume <message@bottle.org> - 2021-10-06 19:07 +0200
      Re: C23 (C2x) changes David Brown <david.brown@hesbynett.no> - 2021-10-07 11:06 +0200
        Re: C23 (C2x) changes Guillaume <message@bottle.org> - 2021-10-07 19:31 +0200
          Re: C23 (C2x) changes David Brown <david.brown@hesbynett.no> - 2021-10-07 22:14 +0200
            Re: C23 (C2x) changes Thiago Adams <thiago.adams@gmail.com> - 2021-10-08 06:18 -0700
              Re: C23 (C2x) changes Thiago Adams <thiago.adams@gmail.com> - 2021-10-08 06:21 -0700
      Re: C23 (C2x) changes Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-29 04:01 -0700
    Re: C23 (C2x) changes Bonita Montero <Bonita.Montero@gmail.com> - 2021-10-15 12:59 +0200
      Re: C23 (C2x) changes Jim Jackson <jj@franjam.org.uk> - 2021-10-15 16:50 +0000
        Re: C23 (C2x) changes Bonita Montero <Bonita.Montero@gmail.com> - 2021-10-16 07:51 +0200
          Re: C23 (C2x) changes "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-10-16 11:50 -0700
            Re: C23 (C2x) changes Bonita Montero <Bonita.Montero@gmail.com> - 2021-10-16 21:28 +0200
              Re: C23 (C2x) changes Jim Jackson <jj@franjam.org.uk> - 2021-10-17 17:18 +0000
                Re: C23 (C2x) changes Bonita Montero <Bonita.Montero@gmail.com> - 2021-10-17 20:00 +0200
                Re: C23 (C2x) changes Bart <bc@freeuk.com> - 2021-10-17 19:17 +0100
                Re: C23 (C2x) changes Bonita Montero <Bonita.Montero@gmail.com> - 2021-10-18 06:49 +0200
                Re: C23 (C2x) changes Bart <bc@freeuk.com> - 2021-10-18 11:23 +0100
                Re: C23 (C2x) changes Bonita Montero <Bonita.Montero@gmail.com> - 2021-10-18 14:09 +0200
                Re: C23 (C2x) changes Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-21 01:07 +0000
                Re: C23 (C2x) changes Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-21 01:02 +0000
          Re: C23 (C2x) changes Guillaume <message@bottle.org> - 2021-10-16 21:28 +0200
            Re: C23 (C2x) changes Bonita Montero <Bonita.Montero@gmail.com> - 2021-10-17 06:04 +0200
              Re: C23 (C2x) changes Manfred <noname@add.invalid> - 2021-10-17 19:35 +0200
                Re: C23 (C2x) changes Bonita Montero <Bonita.Montero@gmail.com> - 2021-10-17 20:01 +0200
                Re: C23 (C2x) changes "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-10-17 14:15 -0700
              Re: C23 (C2x) changes Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-21 01:02 +0000
                Re: C23 (C2x) changes Bonita Montero <Bonita.Montero@gmail.com> - 2021-10-21 13:15 +0200

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