On Fri, Nov 9, 2012 at 9:13 PM, Richard Smith <[email protected]> wrote:
> On Thu, Nov 8, 2012 at 5:49 PM, Ryan Molden <[email protected]> wrote: > > This is a re-submission of an older proposed patch > > ( > http://www.mail-archive.com/[email protected]/msg55616/0001-Added-support-for-MSVC-2012-type-traits-used-in-stan.patch > ) > > that João hadn't had time to write tests for (which were requested with > the > > original submission review). > > > > The only changes I made from the original (apart from adding tests) was > to > > take out the bail-out for hasTrivialMoveAssignment from > > UTT_HasNothrowMoveAssign in EvaluateUnaryTypeTrait (in > > lib\Sema\SemaExprCXX.cpp). > > > > My reasoning was that trivial move assignment operators (which I > understand > > to be implicitly generated ones, please correct me if this is mistaken) > can > > actually have non-empty exception specifiers if any of the member > > move-assignment operators they invoke have such non-empty exception > > specifiers. > > > > Specifically: > > > > n3376 15.4 [except.spec]/14 > > > > An inheriting constructor (12.9) and an implicitly declared special > member > > function (Clause 12) have an exception-specification. If f is an > inheriting > > constructor or an implicitly declared default constructor, copy > constructor, > > move constructor, destructor, copy assignment operator, or move > assignment > > operator, its implicit exception-specification specifies the type-id T if > > and only if T is allowed by the exception-specification of a function > > directly invoked by f’s implicit definition; f allows all exceptions if > any > > function it directly invokes allows all exceptions, and f has the > > exception-specification noexcept(true) if every function it directly > invokes > > allows no exceptions. [ Note: An instantiation of an inheriting > constructor > > template has an implied exception-specification as if it were a > non-template > > inheriting constructor.] > > > > so I would expect this class (HasMemberThrowMoveAssign) to fail for > > std::is_nothrow_move_assignable: > > > > struct NonPOD { NonPOD(int); }; enum Enum { EV }; struct POD { Enum e; > int > > i; float f; NonPOD* p; }; > > > > struct HasThrowMoveAssign { HasThrowMoveAssign& operator =(const > > HasThrowMoveAssign&&) throw(POD); }; > > struct HasMemberThrowMoveAssign { HasThrowMoveAssign member; }; > > > > even though it should have a trivial move-assignment operator generated. > > Please correct me if I am mistaken here as my standards reading FU > is...not > > strong. > > You are mistaken here ;-) > > HasMemberThrowMoveAssign's move assignment is not trivial because it > calls a non-trivial move assignment operator. It is possible to have a > throwing trivial move assignment operator, but only if it is deleted. > In that case, the trait should presumbly return false. > Great, thanks for the catch. So it seems that having the early bail-out for things with trivial move assignment operators is correct. I put it back in and all tests are still passing (I thought one of them was failing before I took it out, but that was a week+ ago, so perhaps I am just mis-remembering). It isn't clear how I would make a 'throwing trivial move assignment operator', if you have suggestions I can certainly add a test for it. New patch attached that simply syncs to tip and adds back the bail-out for types with a trivial move-assignment operator. Ryan
Support-For-MSVC-2012-Type-Traits-For-STL.patch
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