Groups > comp.lang.c++ > #82078

Re: I think references should have been const by default

From	James Kuyper <jameskuyper@alumni.caltech.edu>
Newsgroups	comp.lang.c++
Subject	Re: I think references should have been const by default
Date	2021-10-25 13:14 -0400
Organization	A noiseless patient Spider
Message-ID	<sl6oln$odm$1@dont-email.me> (permalink)
References	(11 earlier) <sl5pdi$4au$1@gioia.aioe.org> <sl5ug4$qov$1@gioia.aioe.org> <sl6ecq$11uu$1@gioia.aioe.org> <sl6go4$pjq$1@dont-email.me> <sl6l56$10d6$1@gioia.aioe.org>

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On 10/25/21 12:14 PM, RacingRabbit@watershipdown.co.uk wrote:
...
> Any attempt to write to a read only program text area will result in a crash
> regardless of the language.

Perhaps that is true at the hardware level, on some processors. However,
there's also some processors which don't even have the concept of
read-only memory, and there are fully conforming C implementation that
can target some of those processors.

However, I'm talking about the level of C code, not hardware. The
translation from C code to machine code is defined only in terms of the
required behavior, and when there is NO required behavior, that
translation can get distinctly weird if you believe the mistaken idea
that C is a "portable assembler".

> ... It is implicit that its read only in C because
> C also provides the following initialisation which places the string 
> (presumably) on the heap:
> 
> char str[] = "hello world";

Such code cannot result in the string being placed in read-only memory,
because it's perfectly legal to modify str. On the other hand, both of
the following C declarations do allow strings to be placed in read-only
memory, even if they occur at block scope:

    const char str[] = "Hello world!";
    char *strptr = "Good bye!";

The first one is allowed to be placed in read-only memory because the
object str is declared "const". The second is allowed to be placed in
read-only memory because it's undefined behavior to write to the memory
pointed at by by strptr, despite the fact that, in C, the string literal
does NOT have the type const char[10], as it would in C++.

However, just because it would be permissible for an implementation to
place those objects in read-only memory, it's not actually required that
they be placed there. Many implementations won't do so, especially if
those declarations occur at block scope.

And even if they were placed in read-only memory, writing C code that
attempts to modify that memory need not result in machine language
instructions being executed to attempt such a read. Because the behavior
of such code is undefined, an implementation is free to translate such
source code into machine code that does nothing of the kind - and this
is, in fact, the natural result, in some contexts, of certain optimizations.

Thread

I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-21 05:23 +0000
  Re: I think references should have been const by default David Brown <david.brown@hesbynett.no> - 2021-10-21 08:54 +0200
    Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-21 09:48 +0000
      Re: I think references should have been const by default Paavo Helde <myfirstname@osa.pri.ee> - 2021-10-21 12:55 +0300
      Re: I think references should have been const by default David Brown <david.brown@hesbynett.no> - 2021-10-21 12:57 +0200
        Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-21 13:40 +0000
          Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-21 15:04 +0100
            Re: I think references should have been const by default Manfred <noname@add.invalid> - 2021-10-21 16:41 +0200
              Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-21 14:57 +0000
            Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-21 14:51 +0000
            Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-21 12:09 -0400
              Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-21 23:49 +0100
                Re: I think references should have been const by default "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2021-10-21 16:21 -0700
                Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-22 16:14 +0100
                Re: I think references should have been const by default Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-22 12:04 -0700
                Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-22 20:47 +0100
                Re: I think references should have been const by default Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-22 13:29 -0700
                Re: I think references should have been const by default David Brown <david.brown@hesbynett.no> - 2021-10-23 11:54 +0200
                Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-23 11:22 +0100
                Re: I think references should have been const by default David Brown <david.brown@hesbynett.no> - 2021-10-23 12:35 +0200
                Re: I think references should have been const by default Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-10-23 13:23 +0100
                Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-23 13:57 +0100
                Re: I think references should have been const by default Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-10-23 21:02 +0100
                Re: I think references should have been const by default Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-23 15:07 -0700
                Re: I think references should have been const by default Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-23 21:15 -0700
                Re: I think references should have been const by default Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-23 21:12 -0700
              Re: I think references should have been const by default David Brown <david.brown@hesbynett.no> - 2021-10-22 11:13 +0200
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-22 19:18 -0400
            Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-22 04:41 +0000
              Re: I think references should have been const by default Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2021-10-23 21:30 +0100
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-25 04:51 +0000
                Re: I think references should have been const by default Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2021-10-26 00:53 +0100
            Re: I think references should have been const by default David Brown <david.brown@hesbynett.no> - 2021-10-22 09:46 +0200
              Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-22 15:48 +0100
                Re: I think references should have been const by default David Brown <david.brown@hesbynett.no> - 2021-10-23 12:21 +0200
                Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-23 12:06 +0100
                Re: I think references should have been const by default David Brown <david.brown@hesbynett.no> - 2021-10-23 18:45 +0200
                Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-23 18:58 +0100
                Re: I think references should have been const by default David Brown <david.brown@hesbynett.no> - 2021-10-24 12:11 +0200
                Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-24 23:11 +0100
                Re: I think references should have been const by default Öö Tiib <ootiib@hot.ee> - 2021-10-24 16:18 -0700
                Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-25 00:58 +0100
                Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-25 08:21 +0000
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-25 09:47 +0000
                Re: I think references should have been const by default Bo Persson <bo@bo-persson.se> - 2021-10-25 12:33 +0200
                Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-25 14:19 +0000
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-25 10:59 -0400
                Re: I think references should have been const by default Manfred <noname@add.invalid> - 2021-10-25 17:56 +0200
                Re: I think references should have been const by default Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-25 11:11 -0700
                Re: I think references should have been const by default Manfred <noname@add.invalid> - 2021-10-26 17:15 +0200
                Re: I think references should have been const by default Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-29 06:41 -0700
                Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-25 16:14 +0000
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-25 13:14 -0400
                Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-26 08:18 +0000
                Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-26 12:39 +0100
                Re: I think references should have been const by default Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-10-26 14:29 +0100
                Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-26 15:11 +0100
                Re: I think references should have been const by default Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-26 09:49 -0700
                Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-26 18:38 +0100
                Re: I think references should have been const by default Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-26 11:20 -0700
                Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-26 20:32 +0100
                Re: I think references should have been const by default David Brown <david.brown@hesbynett.no> - 2021-10-26 22:18 +0200
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-27 04:43 +0000
                Re: I think references should have been const by default David Brown <david.brown@hesbynett.no> - 2021-10-27 08:29 +0200
                Re: I think references should have been const by default Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-29 06:32 -0700
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-11-01 06:12 +0000
                Re: I think references should have been const by default David Brown <david.brown@hesbynett.no> - 2021-11-01 08:53 +0100
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-11-01 11:26 -0400
                Re: I think references should have been const by default "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2021-11-02 16:19 +0100
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-11-02 12:54 -0400
                Re: I think references should have been const by default Paavo Helde <myfirstname@osa.pri.ee> - 2021-11-02 23:49 +0200
                Re: I think references should have been const by default "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2021-11-03 00:38 +0100
                Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-26 14:36 +0000
                Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-26 15:55 +0100
                Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-26 15:26 +0000
                Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-26 20:35 +0100
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-27 04:44 +0000
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-26 11:27 -0400
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-26 10:31 -0400
                Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-26 14:42 +0000
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-26 11:22 -0400
                Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-26 15:30 +0000
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-26 12:23 -0400
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-26 12:51 -0400
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-26 14:34 -0400
                Re: I think references should have been const by default "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-10-26 12:57 -0700
                Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-27 07:57 +0000
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-27 08:47 +0000
                Re: I think references should have been const by default JohnnyCameLater@whatsthetime.net - 2021-10-27 14:29 +0000
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-28 05:17 +0000
                Re: I think references should have been const by default JohnnyCameLater@whatsthetime.net - 2021-10-28 09:30 +0000
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-29 04:47 +0000
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-29 05:11 +0000
                Re: I think references should have been const by default JohnnyCameLater@whatsthetime.net - 2021-10-29 08:40 +0000
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-11-01 06:15 +0000
                Re: I think references should have been const by default David Brown <david.brown@hesbynett.no> - 2021-10-27 11:07 +0200
                Re: I think references should have been const by default JohnnyCameLater@whatsthetime.net - 2021-10-27 14:30 +0000
                Re: I think references should have been const by default David Brown <david.brown@hesbynett.no> - 2021-10-27 17:30 +0200
                Re: I think references should have been const by default JohnnyCameLater@whatsthetime.net - 2021-10-27 15:46 +0000
                Re: I think references should have been const by default scott@slp53.sl.home (Scott Lurndal) - 2021-10-27 16:13 +0000
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-27 11:39 -0400
                Re: I think references should have been const by default JohnnyCameLater@whatsthetime.net - 2021-10-27 15:51 +0000
                Re: I think references should have been const by default Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-10-27 17:21 +0100
                Re: I think references should have been const by default JohnnyCameLater@whatsthetime.net - 2021-10-28 09:29 +0000
                Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-28 11:20 +0100
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-27 12:26 -0400
                Re: I think references should have been const by default Anand Hariharan <mailto.anand.hariharan@gmail.com> - 2021-10-31 09:22 -0700
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-11-01 00:13 -0400
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-28 05:20 +0000
                Re: I think references should have been const by default "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-10-27 23:10 -0700
                Re: I think references should have been const by default JohnnyCameLater@whatsthetime.net - 2021-10-28 09:30 +0000
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-29 04:51 +0000
                Re: I think references should have been const by default JohnnyCameLater@whatsthetime.net - 2021-10-29 08:39 +0000
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-11-01 06:34 +0000
                Re: I think references should have been const by default Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2021-10-27 17:41 +0100
                Re: I think references should have been const by default David Brown <david.brown@hesbynett.no> - 2021-10-27 19:02 +0200
                Re: I think references should have been const by default Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2021-10-27 18:21 +0100
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-27 11:38 -0400
                Re: I think references should have been const by default JohnnyCameLater@whatsthetime.net - 2021-10-27 15:49 +0000
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-27 12:36 -0400
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-27 04:57 +0000
                Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-25 18:19 +0100
                Re: I think references should have been const by default Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-25 10:48 -0700
                Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-26 08:21 +0000
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-26 08:37 +0000
                Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-26 09:02 +0000
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-26 11:14 +0000
                Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-26 14:35 +0000
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-27 05:01 +0000
                Re: I think references should have been const by default Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-29 06:34 -0700
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-26 10:43 -0400
                Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-26 15:21 +0000
                Re: I think references should have been const by default David Brown <david.brown@hesbynett.no> - 2021-10-26 22:32 +0200
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-27 05:04 +0000
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-26 10:42 -0400
                Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-26 14:48 +0000
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-26 11:52 -0400
                Re: I think references should have been const by default Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-26 10:22 -0700
                Re: I think references should have been const by default Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-26 10:27 -0700
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-26 14:06 -0400
                Re: I think references should have been const by default Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-29 06:45 -0700
                Re: I think references should have been const by default Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-29 11:11 -0700
                Re: I think references should have been const by default Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-04-25 07:39 -0700
                Re: I think references should have been const by default Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-04-25 10:59 -0700
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-26 05:29 +0000
                Re: I think references should have been const by default David Brown <david.brown@hesbynett.no> - 2021-10-26 08:53 +0200
                Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-26 08:23 +0000
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-26 08:40 +0000
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-26 05:18 +0000
                Re: I think references should have been const by default David Brown <david.brown@hesbynett.no> - 2021-10-26 09:07 +0200
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-26 11:03 -0400
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-25 10:39 -0400
                Re: I think references should have been const by default Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-25 10:56 -0700
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-25 10:30 -0400
                Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-25 14:39 +0000
                Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-25 11:05 -0400
                Re: I think references should have been const by default "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-10-25 12:45 -0700
                Re: I think references should have been const by default "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-10-26 11:20 -0700
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-25 05:00 +0000
                Re: I think references should have been const by default Bart <bc@freeuk.com> - 2021-10-25 12:13 +0100
                Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-26 05:36 +0000
                Re: I think references should have been const by default Manfred <noname@add.invalid> - 2021-10-25 16:58 +0200
    Re: I think references should have been const by default "daniel...@gmail.com" <danielaparker@gmail.com> - 2021-10-22 12:28 -0700
  Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-21 09:12 +0000
    Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-21 09:52 +0000
      Re: I think references should have been const by default RacingRabbit@watershipdown.co.uk - 2021-10-21 10:36 +0000
        Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-22 04:45 +0000
    Re: I think references should have been const by default James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-21 12:07 -0400
  Re: I think references should have been const by default Paavo Helde <myfirstname@osa.pri.ee> - 2021-10-21 12:18 +0300
  Re: I think references should have been const by default Bonita Montero <Bonita.Montero@gmail.com> - 2021-10-21 13:13 +0200
    Re: I think references should have been const by default Bo Persson <bo@bo-persson.se> - 2021-10-21 15:08 +0200
    Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-22 04:45 +0000
      Re: I think references should have been const by default Bonita Montero <Bonita.Montero@gmail.com> - 2021-10-22 07:55 +0200
        Re: I think references should have been const by default Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-22 11:21 +0000
  Re: I think references should have been const by default "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2021-10-21 13:22 +0200
    Re: I think references should have been const by default Juha Nieminen <nospam@thanks.invalid> - 2021-10-22 04:48 +0000
  Re: I think references should have been const by default Manfred <noname@add.invalid> - 2021-10-21 13:57 +0200
  Re: I think references should have been const by default Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-21 21:27 +0000
  Re: I think references should have been const by default Jorgen Grahn <grahn+nntp@snipabacken.se> - 2021-10-24 14:20 +0000

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