[PATCH] Sema: reject probably incorrect atomic ordering requests

[JF Bastien]

What I mean is: does each Sema check has to deal with this (and pessimize
all errors to warnings), or should Sema figure out what code isn't
reachable?


On Tue, Mar 11, 2014 at 1:07 PM, Richard Smith <richard at metafoo.co.uk>wrote:

> Per C11 7.1.4/1, providing an invalid value for a library function
> argument results in undefined behavior, and it's generally accepted that we
> can only reject a program that has undefined behavior if the undefined
> behavior is guaranteed to occur (either because it occurs during
> translation or because it occurs on every execution of the program). So an
> error is not allowed here, but a warning is fine.
>
>
> On Tue, Mar 11, 2014 at 12:38 PM, JF Bastien <jfb at google.com> wrote:
>
>> Isn't that the case with any errors that can crop up in control-flow
>> sensitive manners, through template magic or tautological compares and
>> such? I assume David has a better informed opinion on this than I do.
>>
>>
>> On Tue, Mar 11, 2014 at 12:21 PM, Tim Northover <t.p.northover at gmail.com>wrote:
>>
>>> Hi JF,
>>>
>>> Thanks for taking a look.
>>>
>>> On 11 March 2014 04:59, JF Bastien <jfb at google.com> wrote:
>>> > lgtm after adding tests of missing __c11_atomic_* to
>>> test/Sema/atomic-ops.c,
>>> > especially load_n/store_n.
>>>
>>> I committed it with a full set of tests (r203561), and then changed it
>>> to a warning (r203564) when I realised valid programs could contain
>>> statements like:
>>>
>>> if (0) {
>>>   __c11_atomic_load(ptr, memory_order_release);
>>> }
>>>
>>> or possibly even some sane equivalent via templates or other weirdness.
>>>
>>> Cheers.
>>>
>>> Tim.
>>>
>>
>>
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>>
>
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