From 70192a9efb72800cd83f09496f5168332c46f060 Mon Sep 17 00:00:00 2001 From: Eric Fiselier Date: Wed, 26 Aug 2015 20:15:02 +0000 Subject: [libcxx] Rewrite C++03 __invoke. Summary: This patch rewrites the C++03 `__invoke` and related meta-programming. There are a number of major changes. `__invoke` in C++03 now has a fallback overload for when the invoke expression is ill-formed (similar to C++11). This means that the `__invoke_return` traits will return `__nat` when `__invoke(...)` is ill formed. This would previously cause a compile error. Bullets 1-4 of `__invoke` have been rewritten. In the old version `__invoke` had 32 overloads for bullets 1 and 2, one for each possible cv-qualified function signature with arities 0-3. 64 overloads would be needed to support member functions with varargs. Currently these overloads were fundamentally broken. An example overload looked like: ``` template Rp __invoke(Rp (Tp::*pm)(A0) const, T1&, A0&) ``` Because `A0` appeared in two different deducible contexts it would have to deduce to be an exact match or the overload would be rejected. This is made even worse because `A0` appears without a reference qualifier in the member function signature and with a reference qualifier as an `__invoke` parameter. This means that only member functions that took all of their arguments by value could be matched. One possible fix would be to make the second occurrence of `A0` appear in a non-deducible context. This way any type convertible to `A0` could be passed as the first parameter. The benefit of this approach is that the signature of the member function enforces the arity and types taken by the `__invoke` signature it generates. However nothing in the `INVOKE` specification requires this behavior. My solution is to use a `__invoke_enable_if` metafunction to selectively enable the `__invoke` overloads for bullets 1, 2, 3 and 4. It uses `__member_function_traits` to inspect and extract the return type and class type of the pointer to member. Using `__member_function_traits` to inspect `PM_Type` also allows us to reduce the number of `__invoke` overloads from 32 to 8 and add varargs support at the same time. Because `__invoke_enable_if` knows the exact return type of `__invoke` for bullets 1-4 we no longer need to use `decltype(__invoke(...))` to compute the return type in the `__invoke_return*` traits. This will reduce the problems caused by `#define decltype(X) __typeof__(X)` in C++03. Tests for this change have already been committed. All tests in `test/std/utilities/function.objects` now pass in C++03, previously there were 20 failures. Reviewers: K-ballo, howard.hinnant, mclow.lists Subscribers: cfe-commits Differential Revision: http://reviews.llvm.org/D11553 llvm-svn: 246068 --- .../utilities/function.objects/refwrap/refwrap.const/type_ctor.fail.cpp | 2 ++ 1 file changed, 2 insertions(+) (limited to 'libcxx/test/std/utilities/function.objects/refwrap/refwrap.const') diff --git a/libcxx/test/std/utilities/function.objects/refwrap/refwrap.const/type_ctor.fail.cpp b/libcxx/test/std/utilities/function.objects/refwrap/refwrap.const/type_ctor.fail.cpp index ba46946aae1..a2316063cec 100644 --- a/libcxx/test/std/utilities/function.objects/refwrap/refwrap.const/type_ctor.fail.cpp +++ b/libcxx/test/std/utilities/function.objects/refwrap/refwrap.const/type_ctor.fail.cpp @@ -13,6 +13,8 @@ // reference_wrapper(T&&) = delete; +// XFAIL: c++98, c++03 + #include #include -- cgit v1.2.3