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[Bug target/19293] avr-gcc crashes when using shifts with negative shift count
- From: "joseph at codesourcery dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 6 Jan 2005 18:03:25 -0000
- Subject: [Bug target/19293] avr-gcc crashes when using shifts with negative shift count
- References: <20050106160127.19293.bjoern.m.haase@web.de>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Additional Comments From joseph at codesourcery dot com 2005-01-06 18:03 -------
Subject: Re: avr-gcc crashes when using shifts with negative
shift count
On Thu, 6 Jan 2005, bjoern dot m dot haase at web dot de wrote:
> It seems that the standard says that shift operations with negative shift count
> are supposed to yield an "unspecified" result.
Undefined, not unspecified.
> Is there some more specific convention for gcc on how to behave in these cases?
For some other cases of runtime undefined behavior we generate an abort
(with a warning that we are doing so). This is what we do for va_arg with
types changed by the default argument promotions, and for calls to
functions cast to incompatible types. We could do it for negative or
too-wide shifts as well if we wish, either generally or for the specific
targets for which they are problems.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19293