Re: Initializing a malloc'ed struct whose fields are const with run-time values

Message-ID	<e4d3t9-6br.ln1@wilbur.25thandClement.com> (permalink)
From	William Ahern <william@wilbur.25thandClement.com>
Subject	Re: Initializing a malloc'ed struct whose fields are const with run-time values
Newsgroups	comp.lang.c
References	<kdmbl7$4lc$1@dont-email.me> <0.7432cc83d523a65ab134.20130122211350GMT.87ehhc53ap.fsf@bsb.me.uk>
Date	2013-01-22 13:32 -0800

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Ben Bacarisse <ben.usenet@bsb.me.uk> wrote:
> Noob <root@127.0.0.1> writes:
<snip>
> > 2) I'm not sure it is well-defined to memcpy stuff into some const
> > fields. Does it tickle the cranky UB gods?

> No, I think it's fine.  You are not modifying anything that is const.
> malloced storage has no declared type and the memcpy probably makes the
> effective type a byte array.

C99 (N1256) 6.5p6:

	If a value is copied into an object having no declared type using
	memcpy or memmove, or is copied as an array of character type, then
	the effective type of the modified object for that access and for
	subsequent accesses that do not modify the value is the effective
	type of the object from which the value is copied, if it has one.

I guess the effective type arises only after memcpy completes.

Thread

Initializing a malloc'ed struct whose fields are const with run-time values Noob <root@127.0.0.1> - 2013-01-22 16:36 +0100
  Re: Initializing a malloc'ed struct whose fields are const with run-time values Shao Miller <sha0.miller@gmail.com> - 2013-01-22 11:23 -0500
    Re: Initializing a malloc'ed struct whose fields are const with run-time values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-22 21:26 +0000
      Re: Initializing a malloc'ed struct whose fields are const with run-time values James Kuyper <jameskuyper@verizon.net> - 2013-01-22 16:41 -0500
    Re: Initializing a malloc'ed struct whose fields are const with run-time values William Ahern <william@wilbur.25thandClement.com> - 2013-01-22 13:25 -0800
      Re: Initializing a malloc'ed struct whose fields are const with run-time values Shao Miller <sha0.miller@gmail.com> - 2013-01-22 23:17 -0500
    Re: Initializing a malloc'ed struct whose fields are const with run-time values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-23 13:09 +0000
      Re: Initializing a malloc'ed struct whose fields are const with run-time values Noob <root@127.0.0.1> - 2013-01-23 14:16 +0100
        Re: Initializing a malloc'ed struct whose fields are const with run-time values "BartC" <bc@freeuk.com> - 2013-01-23 13:25 +0000
          Re: Initializing a malloc'ed struct whose fields are const with run-time values Noob <root@127.0.0.1> - 2013-01-23 15:21 +0100
            Re: Initializing a malloc'ed struct whose fields are const with run-time values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-23 14:56 +0000
              Re: Initializing a malloc'ed struct whose fields are const with run-time values Noob <root@127.0.0.1> - 2013-01-23 16:40 +0100
                Re: Initializing a malloc'ed struct whose fields are const with run-time values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-23 18:26 +0000
                Re: Initializing a malloc'ed struct whose fields are const with run-time values Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-23 20:39 -0800
            Re: Initializing a malloc'ed struct whose fields are const with run-time values Shao Miller <sha0.miller@gmail.com> - 2013-01-23 17:14 -0500
  Re: Initializing a malloc'ed struct whose fields are const with run-time values Ike Naar <ike@sverige.freeshell.org> - 2013-01-22 17:59 +0000
    Re: Initializing a malloc'ed struct whose fields are const with run-time values Shao Miller <sha0.miller@gmail.com> - 2013-01-22 14:09 -0500
      Re: Initializing a malloc'ed struct whose fields are const with run-time values Noob <root@localhost> - 2013-01-22 21:59 +0100
        Re: Initializing a malloc'ed struct whose fields are const with run-time values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-01-22 21:19 +0000
        Re: Initializing a malloc'ed struct whose fields are const with run-time values Shao Miller <sha0.miller@gmail.com> - 2013-01-22 23:47 -0500
      Re: Initializing a malloc'ed struct whose fields are const with run-time values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-22 21:05 +0000
        Re: Initializing a malloc'ed struct whose fields are const with run-time values Shao Miller <sha0.miller@gmail.com> - 2013-01-22 16:15 -0500
    Re: Initializing a malloc'ed struct whose fields are const with   run-time values Ian Collins <ian-news@hotmail.com> - 2013-01-23 09:43 +1300
      Re: Initializing a malloc'ed struct whose fields are const with   run-time values William Ahern <william@wilbur.25thandClement.com> - 2013-01-22 13:19 -0800
        Re: Initializing a malloc'ed struct whose fields are const with   run-time values William Ahern <william@wilbur.25thandClement.com> - 2013-01-22 13:35 -0800
          Re: Initializing a malloc'ed struct whose fields are const with   run-time values Ian Collins <ian-news@hotmail.com> - 2013-01-23 10:45 +1300
            Re: Initializing a malloc'ed struct whose fields are const with   run-time values Shao Miller <sha0.miller@gmail.com> - 2013-01-22 17:07 -0500
            Re: Initializing a malloc'ed struct whose fields are const with  run-time values Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-22 21:29 -0800
              Re: Initializing a malloc'ed struct whose fields are const with  run-time values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-23 13:54 +0000
                Re: Initializing a malloc'ed struct whose fields are const with  run-time values Shao Miller <sha0.miller@gmail.com> - 2013-01-23 17:08 -0500
                Re: Initializing a malloc'ed struct whose fields are const with    run-time values Ian Collins <ian-news@hotmail.com> - 2013-01-24 11:29 +1300
                Re: Initializing a malloc'ed struct whose fields are const with    run-time values Shao Miller <sha0.miller@gmail.com> - 2013-01-23 18:26 -0500
                Re: Initializing a malloc'ed struct whose fields are const with      run-time values Ian Collins <ian-news@hotmail.com> - 2013-01-24 14:03 +1300
                Re: Initializing a malloc'ed struct whose fields are const with      run-time values Shao Miller <sha0.miller@gmail.com> - 2013-01-23 23:58 -0500
                Re: Initializing a malloc'ed struct whose fields are const with  run-time values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-23 23:36 +0000
                Re: Initializing a malloc'ed struct whose fields are const with  run-time values Ian Collins <ian-news@hotmail.com> - 2013-01-24 13:55 +1300
                Re: Initializing a malloc'ed struct whose fields are const with  run-time values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-24 02:44 +0000
                Re: Initializing a malloc'ed struct whose fields are const with  run-time values Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-23 21:39 -0800
                Re: Initializing a malloc'ed struct whose fields are const with  run-time values Shao Miller <sha0.miller@gmail.com> - 2013-01-24 00:54 -0500
                Re: Initializing a malloc'ed struct whose fields are const with  run-time values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-24 17:56 +0000
                Re: Initializing a malloc'ed struct whose fields are const with  run-time values Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-24 13:58 -0800
        Re: Initializing a malloc'ed struct whose fields are const with   run-time values James Kuyper <jameskuyper@verizon.net> - 2013-01-22 16:37 -0500
          Re: Initializing a malloc'ed struct whose fields are const with  run-time values Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-22 21:22 -0800
      Re: Initializing a malloc'ed struct whose fields are const with  run-time values Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-22 21:06 -0800
        Re: Initializing a malloc'ed struct whose fields are const with  run-time values Ian Collins <ian-news@hotmail.com> - 2013-01-23 19:55 +1300
          Re: Initializing a malloc'ed struct whose fields are const with  run-time values Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-23 00:48 -0800
            Re: Initializing a malloc'ed struct whose fields are const with  run-time values Ian Collins <ian-news@hotmail.com> - 2013-01-23 23:06 +1300
    Re: Initializing a malloc'ed struct whose fields are const with run-time values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-22 21:02 +0000
      Re: Initializing a malloc'ed struct whose fields are const with run-time values Shao Miller <sha0.miller@gmail.com> - 2013-01-22 16:12 -0500
        Re: Initializing a malloc'ed struct whose fields are const with run-time values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-22 22:37 +0000
          Re: Initializing a malloc'ed struct whose fields are const with run-time values Shao Miller <sha0.miller@gmail.com> - 2013-01-22 22:29 -0500
            Re: Initializing a malloc'ed struct whose fields are const with run-time values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-23 04:28 +0000
              Re: Initializing a malloc'ed struct whose fields are const with run-time values Shao Miller <sha0.miller@gmail.com> - 2013-01-23 00:07 -0500
                Re: Initializing a malloc'ed struct whose fields are const with run-time values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-23 14:04 +0000
    Re: Initializing a malloc'ed struct whose fields are const with run-time values Noob <root@localhost> - 2013-01-22 22:10 +0100
  Re: Initializing a malloc'ed struct whose fields are const with run-time values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-22 21:13 +0000
    Re: Initializing a malloc'ed struct whose fields are const with run-time values Shao Miller <sha0.miller@gmail.com> - 2013-01-22 16:25 -0500
      Re: Initializing a malloc'ed struct whose fields are const with run-time values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-22 22:21 +0000
    Re: Initializing a malloc'ed struct whose fields are const with run-time values William Ahern <william@wilbur.25thandClement.com> - 2013-01-22 13:32 -0800
      Re: Initializing a malloc'ed struct whose fields are const with run-time values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-23 03:50 +0000
    Re: Initializing a malloc'ed struct whose fields are const with run-time values Nick Bowler <nbowler@draconx.ca> - 2013-01-22 21:43 +0000
      Re: Initializing a malloc'ed struct whose fields are const with run-time values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-23 03:45 +0000
        Re: Initializing a malloc'ed struct whose fields are const with run-time values Keith Thompson <kst-u@mib.org> - 2013-01-24 08:23 -0800
  Re: Initializing a malloc'ed struct whose fields are const with run-time values Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-22 20:48 -0800

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