From: "James K. Lowden" <jklowden@schemamania.org>
To: gcc-help@gcc.gnu.org
Subject: Re: how to make gcc warn about arithmetic signed overflow
Date: Mon, 23 Sep 2013 04:04:00 -0000 [thread overview]
Message-ID: <20130923000355.fa2a964c.jklowden@schemamania.org> (raw)
In-Reply-To: <CAH6eHdQzJNQY4Meysi259RheSaGscKUF28OW43OvOD1rf6FkxQ@mail.gmail.com>
On Sat, 21 Sep 2013 19:30:02 +0100
Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
> > its value can be changed using pointers
>
> No, that's not true. You can't change the value of a const object in a
> valid program.
I don't know if we're talking C or C++ at this point, but const_cast
will surely let you change the value of a const object without treading
into undefined behavior.
Regarding the OP's query
> > int r = ab * bc;
although the provided example is simple enough, it's the compiler's
job is to generate object code, not to do static analysis.
Even if the values are const, in the general case they could be
modified by another module or another thread. The compiler simply
doesn't have enough information to warn of every runtime overflow.
--jkl
next prev parent reply other threads:[~2013-09-23 4:04 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-21 16:45 wempwer
2013-09-21 17:24 ` Jonathan Wakely
2013-09-21 17:41 ` wempwer
2013-09-21 18:30 ` Jonathan Wakely
2013-09-21 18:50 ` wempwer
2013-09-21 19:55 ` Jędrzej Dudkiewicz
2013-09-21 20:16 ` wempwer
2013-09-21 20:52 ` Jędrzej Dudkiewicz
2013-09-21 21:07 ` wempwer
2013-09-23 4:04 ` James K. Lowden [this message]
2013-09-23 7:55 ` Jonathan Wakely
2013-09-23 15:47 ` James K. Lowden
2013-09-23 21:50 ` Jonathan Wakely
2013-09-23 22:44 ` James K. Lowden
2013-09-23 23:20 ` Jonathan Wakely
2013-09-23 19:38 ` Dave Allured - NOAA Affiliate
2013-09-23 19:43 ` Oleg Endo
2013-09-23 20:37 ` Dave Allured - NOAA Affiliate
2013-09-23 19:48 ` Andrew Haley
2013-09-23 22:00 ` James K. Lowden
2013-09-24 17:48 ` Andrew Haley
2013-09-26 2:30 ` James K. Lowden
2013-09-26 8:29 ` Vincent Lefevre
2013-09-26 14:49 ` Andrew Haley
2013-09-26 17:03 ` Vincent Lefevre
2013-09-26 18:19 ` Andrew Haley
2013-09-27 7:58 ` Vincent Lefevre
2013-09-27 8:23 ` Andrew Haley
2013-09-27 9:28 ` Vincent Lefevre
2013-09-27 9:43 ` Andrew Haley
2013-09-26 17:41 ` Andrew Haley
2013-09-24 7:42 ` Brian Drummond
2013-09-21 17:53 ` Marc Glisse
2013-09-21 18:09 ` wempwer
2013-09-21 18:27 ` Jonathan Wakely
2013-09-21 19:32 ` wempwer
2013-09-22 15:52 ` Jonathan Wakely
2013-09-23 13:04 ` David Brown
2013-09-21 17:36 ` Brian Drummond
2013-09-21 17:45 ` wempwer
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