[Patch] Disable -Wtaulological-compare for substituted template types

[Richard Trieu]

Added test case in r193890.


On Fri, Nov 1, 2013 at 3:00 PM, David Blaikie <dblaikie at gmail.com> wrote:

> Cool - perhaps add a test case for the non-type template parameter case as
> well? Though it's not really necessary. Up to you.
>
>
> On Fri, Nov 1, 2013 at 2:54 PM, Richard Trieu <rtrieu at google.com> wrote:
>
>> Committed in r193887 and r193888
>>
>>
>> On Fri, Nov 1, 2013 at 1:02 PM, David Blaikie <dblaikie at gmail.com> wrote:
>>
>>>
>>>
>>>
>>> On Fri, Nov 1, 2013 at 12:15 PM, Arthur O'Dwyer <
>>> arthur.j.odwyer at gmail.com> wrote:
>>>
>>>> On Thu, Oct 31, 2013 at 5:52 PM, Richard Trieu <rtrieu at google.com>
>>>> wrote:
>>>> > On Thu, Oct 31, 2013 at 4:25 PM, David Blaikie <dblaikie at gmail.com>
>>>> wrote:
>>>> >>
>>>> >> Could we just restrict these warnings to only be done on template
>>>> >> patterns, not template specializations? (I know Ted's had some
>>>> concern about
>>>> >> doing work on template patterns in the past because he believed that
>>>> might
>>>> >> create too much work analyzing templates that are never instantiated,
>>>> >> though)
>>>> >
>>>> > I think that would be possible and a cleaner way of approaching this.
>>>> > Currently, Clang warns in both template patters and specializations.
>>>>  That
>>>> > means if you have :
>>>> >
>>>> > template<int Num>
>>>> > bool greater(unsigned Val) {
>>>> >   return Val >= 0;
>>>> > }
>>>> >
>>>> > ... greater<0>(42); ...
>>>> > ... greater<1>(42); ...
>>>> > ... greater<2>(42); ...
>>>> >
>>>> > There would be four warnings on the return line.  Ignoring the three
>>>> > warnings in the specializations and only showing the one from the
>>>> template
>>>> > pattern would be best on cutting down the noise.
>>>>
>>>> Only for -Wtautological-compare, though, right?
>>>>
>>>> I imagine that there are plenty of warnings that would be useful to
>>>> produce during template instantiation, but impossible to detect by
>>>> just looking at the pattern (without checking dependent
>>>> types/expressions). A trivial example would be
>>>> -Wuninitialized for this code:
>>>>
>>>>     template<typename T> T newval() { T t; return t; }
>>>>
>>>> Here, newval<int>() has undefined behavior, but newval<std::string>()
>>>> is perfectly correct.
>>>>
>>>> So whereas -Wtautological-compare empirically gives almost 100% false
>>>> positives on dependent expressions, -Wuninitialized probably gives
>>>> 100% *true* positives.
>>>
>>>
>>> Certainly. There are many warnings in each of these buckets, but
>>> generally a given warning falls into only one - either it should be done on
>>> instantiations or patterns. (there are some similar issues with macros and
>>> other things (sizeof/decltype of implementation-provided types, etc))
>>>
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20131101/bf6c333e/attachment.html>