Re: [Qemu-devel] [PATCH for 2.5] QEMU does not care about left shifts of signed negative values

[Peter Maydell]

On 17 November 2015 at 12:10, Paolo Bonzini <address@hidden> wrote:
> On 17/11/2015 12:22, Peter Maydell wrote:
>>  * gcc need to document this (this is a stronger statement than
>>    what they currently have since it is a guarantee not to change
>>    the semantics in the future if -fwrapv is set)
>
> Actually they document it under -fstrict-overflow ("Using '-fwrapv'
> means that integer signed overflow is fully defined: it wraps") but it
> would be nice to add it under -fwrapv as well.  I'll send a patch.

My interpretation of that quote was that the gcc devs don't include
shifts in their definition of "integer signed overflows" (since
-fwrapv is very clear about what it affects.) Either way clarity
would be good, so thanks for taking on the patch.

thanks
-- PMM