From: Oleg Endo <oleg.endo@t-online.de>
To: Dave Allured - NOAA Affiliate <dave.allured@noaa.gov>
Cc: gcc-help@gcc.gnu.org
Subject: Re: how to make gcc warn about arithmetic signed overflow
Date: Mon, 23 Sep 2013 19:43:00 -0000 [thread overview]
Message-ID: <1379965364.3915.221.camel@yam-132-YW-E178-FTW> (raw)
In-Reply-To: <CALqwTFMfRi6sZY6Ffpdp0E4d4xiJT0EHRUQH-+Oph5c5AWR3-Q@mail.gmail.com>
On Mon, 2013-09-23 at 13:38 -0600, Dave Allured - NOAA Affiliate wrote:
> On Sun, Sep 22, 2013 at 10:03 PM, James K. Lowden
> <jklowden@schemamania.org> wrote:
> > 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.
>
> I believe the CPU overflow flag is updated after most integer
> arithmetic instructions. Does GCC have any facility for checking this
> flag after each integer operation? This would be a runtime check, of
> course, not a compile time check.
>
See -ftrapv option. Although trapping math is not supported on every
target properly.
E.g. http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35412
or SH related http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54272
Cheers,
Oleg
next prev parent reply other threads:[~2013-09-23 19:43 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
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 [this message]
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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