On 26/11/2015 16:55, Peter Maydell wrote:
> This is all talking about in-practice behaviour of the compiler.
> What I'm interested in is what the documented guarantees are.
They are these:
>> Again, the _value_ is perfectly specified by the GCC documentation (and
>> as of this morning, it's pro
On 26 November 2015 at 15:40, Paolo Bonzini wrote:
> On 26/11/2015 16:01, Peter Maydell wrote:
>> I'm confused by all this text about constant expressions. Does
>> -fwrapv guarantee that signed shift of << behaves as we want
>> in all situations (including constant expressions) or doesn't it?
>
>
On 26/11/2015 16:01, Peter Maydell wrote:
> > - regarding overflow, in addition to the weird -Wpedantic warning, GCC 6
> > adds a new -Wshift-overflow flag which is enabled by default in C99 and
> > C11 modes, and which only applies to constant expressions. So the
> > remaining case where the comp
On 26 November 2015 at 13:04, Paolo Bonzini wrote:
>
>
> On 26/11/2015 12:28, Peter Maydell wrote:
>>> But we are relying on them, and thus we should document them. Witness
>>> the number of patches fixing so called "undefined" behavior. And those
>>> patches are _dangerous_.
>>
>> Until and unl
On 26 November 2015 at 12:15, Markus Armbruster wrote:
> Peter Maydell writes:
>> I don't see much point in documenting what we rely on
>> if we can't rely on it and need to stop relying on it.
>
> "Can't" and "need" are too strong. The kernel can, and I fail to see
> what makes us so special th
On 26/11/2015 13:19, Peter Maydell wrote:
> On 26 November 2015 at 12:15, Markus Armbruster wrote:
>> Peter Maydell writes:
>>> I don't see much point in documenting what we rely on
>>> if we can't rely on it and need to stop relying on it.
>>
>> "Can't" and "need" are too strong. The kernel c
On 26/11/2015 12:28, Peter Maydell wrote:
>> But we are relying on them, and thus we should document them. Witness
>> the number of patches fixing so called "undefined" behavior. And those
>> patches are _dangerous_.
>
> Until and unless the compiler guarantees us the semantics that
> we want,
Peter Maydell writes:
> On 26 November 2015 at 11:23, Paolo Bonzini wrote:
>> On 26/11/2015 11:56, Peter Maydell wrote:
>>> It makes a claim about the semantics that the compiler
>>> guarantees us which isn't currently valid. (Or
>>> alternatively, it's implicitly claiming that clang isn't
>>> a
On 26 November 2015 at 11:23, Paolo Bonzini wrote:
> On 26/11/2015 11:56, Peter Maydell wrote:
>> It makes a claim about the semantics that the compiler
>> guarantees us which isn't currently valid. (Or
>> alternatively, it's implicitly claiming that clang isn't
>> a supported compiler, which isn'
On 26/11/2015 11:56, Peter Maydell wrote:
> On 26 November 2015 at 10:40, Paolo Bonzini wrote:
>>
>>
>> On 26/11/2015 10:46, Peter Maydell wrote:
>>> I definitely don't think we should apply the -fwrapv patch yet;
>>> would you mind respinning this pullrequest without it?
>>
>> In what way does
On 26 November 2015 at 10:40, Paolo Bonzini wrote:
>
>
> On 26/11/2015 10:46, Peter Maydell wrote:
>> I definitely don't think we should apply the -fwrapv patch yet;
>> would you mind respinning this pullrequest without it?
>
> In what way does that patch make that thing worse?
It makes a claim a
On 26/11/2015 10:46, Peter Maydell wrote:
> On 25 November 2015 at 17:19, Paolo Bonzini wrote:
>> The following changes since commit 4b6eda626fdb8bf90472c6868d502a2ac09abeeb:
>>
>> Merge remote-tracking branch 'remotes/lalrae/tags/mips-20151124' into
>> staging (2015-11-24 17:05:06 +)
>>
On 25 November 2015 at 17:19, Paolo Bonzini wrote:
> The following changes since commit 4b6eda626fdb8bf90472c6868d502a2ac09abeeb:
>
> Merge remote-tracking branch 'remotes/lalrae/tags/mips-20151124' into
> staging (2015-11-24 17:05:06 +)
>
> are available in the git repository at:
>
>
> g
The following changes since commit 4b6eda626fdb8bf90472c6868d502a2ac09abeeb:
Merge remote-tracking branch 'remotes/lalrae/tags/mips-20151124' into staging
(2015-11-24 17:05:06 +)
are available in the git repository at:
git://github.com/bonzini/qemu.git tags/for-upstream
for you to fet
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