On Fri, Nov 1, 2013 at 12:15 PM, Arthur O'Dwyer <[email protected]>wrote:
> On Thu, Oct 31, 2013 at 5:52 PM, Richard Trieu <[email protected]> wrote: > > On Thu, Oct 31, 2013 at 4:25 PM, David Blaikie <[email protected]> > 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))
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