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Re: "Death To C"

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On 08/05/2015 08:44, asetofsymbols@gmail.com wrote:
> Bart wrote:"
> It's not necessarily slow. If the bounds *are* known, then frequently
> you will also know that accesses are within bounds:
>
> for (i=0; i<=len(A); ++i)
>      A[i]=0;
> "
>
> This is already possible
> If A it is in the stack or global
> than sizeof A should return it's size
> in bytes

When A is not a pointer, then yes it's easy.

> If A it is one malloc return than
> could be possible access A Len in
> bytes from malloc structure

How do you tell if A is a pointer allocated by malloc?

A can be:

* A pointer to a static array

* A pointer to a stack (VLA) array)

* A pointer to the middle of a malloc array (so you can't easily pick up 
the allocated size)

* A pointer to the start of a malloc array, but which occupies only part 
of the allocated block

* A pointer the a fixed array in the middle of a struct

* A pointer to an array which has been allocated outside the C system 
(from the OS, from a foreign function, or even from a malloc belonging 
to a different library)

* And, of course, also a pointer to individual variable, and not an 
array at all.

So it's not that straightforward.

-- 
Bartc

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"Death To C" Lynn McGuire <lmc@winsim.com> - 2015-05-04 14:41 -0500
  Re: "Death To C" Melzzzzz <mel@zzzzz.com> - 2015-05-04 22:16 +0200
    Re: "Death To C" Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-05-04 13:26 -0700
      Re: "Death To C" Melzzzzz <mel@zzzzz.com> - 2015-05-04 22:51 +0200
      Re: "Death To C" Bartc <bc@freeuk.com> - 2015-05-04 22:02 +0100
        Re: "Death To C" Melzzzzz <mel@zzzzz.com> - 2015-05-05 00:06 +0200
  Re: "Death To C" Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-05-04 13:22 -0700
    Re: "Death To C" Melzzzzz <mel@zzzzz.com> - 2015-05-04 22:41 +0200
      Re: "Death To C" Robert Wessel <robertwessel2@yahoo.com> - 2015-05-04 20:25 -0500
        Bounds checking in C (Was: "Death To C") gazelle@shell.xmission.com (Kenny McCormack) - 2015-05-05 02:15 +0000
          Re: Bounds checking in C (Was: "Death To C") BGB <cr88192@hotmail.com> - 2015-05-06 10:23 -0500
        Re: "Death To C" Les Cargill <lcargill99@comcast.com> - 2015-05-04 21:36 -0500
          Re: "Death To C" Robert Wessel <robertwessel2@yahoo.com> - 2015-05-05 01:01 -0500
            Re: "Death To C" Les Cargill <lcargill99@comcast.com> - 2015-05-05 12:23 -0500
          Re: "Death To C" CHIN Dihedral <dihedral88888@gmail.com> - 2015-05-05 03:06 -0700
        Re: "Death To C" Ian Collins <ian-news@hotmail.com> - 2015-05-05 17:43 +1200
          Re: "Death To C" Robert Wessel <robertwessel2@yahoo.com> - 2015-05-05 01:00 -0500
            Re: "Death To C" Robert Wessel <robertwessel2@yahoo.com> - 2015-05-05 01:13 -0500
              Re: "Death To C" Ian Collins <ian-news@hotmail.com> - 2015-05-05 19:15 +1200
                Re: "Death To C" Robert Wessel <robertwessel2@yahoo.com> - 2015-05-05 02:41 -0500
                Re: "Death To C" Ian Collins <ian-news@hotmail.com> - 2015-05-05 20:12 +1200
        Re: "Death To C" glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-05 06:48 +0000
        Re: "Death To C" Bartc <bc@freeuk.com> - 2015-05-05 10:57 +0100
          Re: "Death To C" asetofsymbols@gmail.com - 2015-05-05 16:53 -0700
          Re: "Death To C" Nobody <nobody@nowhere.invalid> - 2015-05-06 08:10 +0100
            Re: "Death To C" Bartc <bc@freeuk.com> - 2015-05-06 09:53 +0100
              Re: "Death To C" Richard Heathfield <rjh@cpax.org.uk> - 2015-05-06 13:49 +0100
                Re: "Death To C" Bartc <bc@freeuk.com> - 2015-05-06 14:29 +0100
                Re: "Death To C" Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-05-06 09:43 -0700
                Re: "Death To C" Bartc <bc@freeuk.com> - 2015-05-06 18:24 +0100
          Re: "Death To C" asetofsymbols@gmail.com - 2015-05-08 00:44 -0700
            Re: "Death To C" Bartc <bc@freeuk.com> - 2015-05-08 13:49 +0100
    Re: "Death To C" Bartc <bc@freeuk.com> - 2015-05-04 22:15 +0100
      Re: "Death To C" BGB <cr88192@hotmail.com> - 2015-05-08 09:09 -0500
    Re: "Death To C" Stephen Sprunk <stephen@sprunk.org> - 2015-05-04 16:18 -0500
    Re: "Death To C" Ian Collins <ian-news@hotmail.com> - 2015-05-05 12:49 +1200
  Re: "Death To C" raltbos@xs4all.nl (Richard Bos) - 2015-05-08 21:52 +0000
  Re: "Death To C" Merikissa <merikissa@no.spam.net> - 2015-05-10 04:04 +0300
  Re: "Death To C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-05-13 08:11 -0700
    Re: "Death To C" David Kleinecke <dkleinecke@gmail.com> - 2015-05-13 10:00 -0700
      Re: "Death To C" Bartc <bc@freeuk.com> - 2015-05-13 18:20 +0100
        Re: "Death To C" David Kleinecke <dkleinecke@gmail.com> - 2015-05-14 10:47 -0700
          Re: "Death To C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-05-14 11:09 -0700
          Re: "Death To C" Bartc <bc@freeuk.com> - 2015-05-15 19:21 +0100
            Re: "Death To C" David Kleinecke <dkleinecke@gmail.com> - 2015-05-16 09:10 -0700
              Re: "Death To C" Bartc <bc@freeuk.com> - 2015-05-16 20:45 +0100
                Re: "Death To C" David Kleinecke <dkleinecke@gmail.com> - 2015-05-17 09:38 -0700
        Re: "Death To C" raltbos@xs4all.nl (Richard Bos) - 2015-05-17 10:47 +0000
          Re: "Death To C" Bartc <bc@freeuk.com> - 2015-05-17 12:20 +0100
      Re: "Death To C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-05-13 10:24 -0700
        Re: "Death To C" David Brown <david.brown@hesbynett.no> - 2015-05-13 22:01 +0200
    Re: "Death To C" Nobody <nobody@nowhere.invalid> - 2015-05-14 07:48 +0100

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