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Re: check integer overflow with GCC 4.5.2

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James Kuyper <jameskuyper@verizon.net> writes:
> On 11/29/2011 10:44 PM, sailer wrote:
>> On Nov 29, 7:59 am, pete <pfil...@mindspring.com> wrote:
>>> sailer wrote:
>>>>  is it safe enough?
>>>
>>> No.
>>>
>>>>          int words;
>>>>         ovf(words, sizeof(int), &bytes, &overflow);
>>>
>>> (words) should be initialized
>>> before its value is passed to ovf().
>>>
>>> --
>>> pete
>> 
>> It's a demo code fragment, I checked the asm code to figure out
>> whether the overflow detection works,
>
> Let that be a lesson: even "demo code fragments" should have defined
> behavior; if they don't, your test becomes meaningless.

Right.  If your code has undefined behavior, an optimizing compiler is
permitted to transform it in ways that depend on the assumption that the
behavior is defined.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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check integer overflow with GCC 4.5.2 sailer <xiangdong.ji@gmail.com> - 2011-11-23 20:25 -0800
  Re: check integer overflow with GCC 4.5.2 pete <pfiland@mindspring.com> - 2011-11-24 00:47 -0500
    Re: check integer overflow with GCC 4.5.2 sailer <xiangdong.ji@gmail.com> - 2011-11-23 22:29 -0800
      Re: check integer overflow with GCC 4.5.2 "Philip Lantz" <prl@canterey.us> - 2011-11-24 01:23 -0800
        Re: check integer overflow with GCC 4.5.2 sailer <xiangdong.ji@gmail.com> - 2011-11-27 23:14 -0800
          Re: check integer overflow with GCC 4.5.2 James Kuyper <jameskuyper@verizon.net> - 2011-11-28 07:04 -0500
          Re: check integer overflow with GCC 4.5.2 Noob <root@127.0.0.1> - 2011-11-29 14:12 +0100
            Re: check integer overflow with GCC 4.5.2 Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-11-29 16:16 +0200
            Re: check integer overflow with GCC 4.5.2 88888 Dihedral <dihedral88888@googlemail.com> - 2011-11-29 06:28 -0800
  Re: check integer overflow with GCC 4.5.2 Robert Wessel <robertwessel2@yahoo.com> - 2011-11-24 00:28 -0600
  Re: check integer overflow with GCC 4.5.2 Vincenzo Mercuri <vincenzo.mercuri@yahoo.it> - 2011-11-24 09:46 +0100
    Re: check integer overflow with GCC 4.5.2 sailer <xiangdong.ji@gmail.com> - 2011-11-24 01:08 -0800
      Re: check integer overflow with GCC 4.5.2 "Philip Lantz" <prl@canterey.us> - 2011-11-24 01:26 -0800
        Re: check integer overflow with GCC 4.5.2 sailer <xiangdong.ji@gmail.com> - 2011-11-27 23:09 -0800
    Re: check integer overflow with GCC 4.5.2 "io_x" <a@b.c.invalid> - 2011-11-24 14:19 +0100
  Re: check integer overflow with GCC 4.5.2 gwowen <gwowen@gmail.com> - 2011-11-24 09:10 -0800
  Re: check integer overflow with GCC 4.5.2 sailer <xiangdong.ji@gmail.com> - 2011-11-27 23:21 -0800
    Re: check integer overflow with GCC 4.5.2 Keith Thompson <kst-u@mib.org> - 2011-11-28 16:31 -0800
      Re: check integer overflow with GCC 4.5.2 Ian Collins <ian-news@hotmail.com> - 2011-11-29 13:53 +1300
  Re: check integer overflow with GCC 4.5.2 sailer <xiangdong.ji@gmail.com> - 2011-11-27 23:34 -0800
    Re: check integer overflow with GCC 4.5.2 pete <pfiland@mindspring.com> - 2011-11-28 18:59 -0500
      Re: check integer overflow with GCC 4.5.2 sailer <xiangdong.ji@gmail.com> - 2011-11-29 19:44 -0800
        Re: check integer overflow with GCC 4.5.2 James Kuyper <jameskuyper@verizon.net> - 2011-11-30 11:08 -0500
          Re: check integer overflow with GCC 4.5.2 Keith Thompson <kst-u@mib.org> - 2011-11-30 09:01 -0800
  Re: check integer overflow with GCC 4.5.2 sailer <xiangdong.ji@gmail.com> - 2011-11-29 19:46 -0800

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