[cfe-commits] [Patch] Implement compiler intrinsics for MSVC 2012 type_traits

[Ryan Molden]

Re-sending, sorry if this is a duplicate, I never saw my other post show
up. I have read first posts take awhile to be approved, but it has been a
few days now, so I am assuming it was not received and sending again.

This is a re-submission of an older proposed patch (
http://www.mail-archive.com/cfe-commits@cs.uiuc.edu/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.

I have spot checked this against VS 2012 the best I can, they don't
generate implicit move-assign yet so most all the unit tests, run against
MSVC 2012 would fail because most of the types in the tests have implicit
move-assigns or can't have user defined move assigns (i.e. the scalar
types).

It isn't clear if scalar types should be passing
is_nothrow_move_assignable, it seems, conceptually, they should trivially
pass muster. I tried reading the standard but it isn't entirely clear to
me. They talk about move-assignment applying to objects, but then define
objects as something with storage, which scalars certainly posses :) If
anyone can clarify things like int, enum, pointer to member, and their
expected results for is_nothrow_move_assignable I am happy to update any
test. Or if you can suggest anything else I missed.

Ryan
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