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 <class Rp, class Tp, class T1, class A0>
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<PM_Type, Tp>` 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
The key changes in this patch are:
1. Remove the zero-argument overload in mem_fn. A member function must always
be invoked with at least one argument, the class instance. The zero-argument
operator()() in mem_fn would cause mem_fn to fail to compile when because
the call to '__invoke(pm)' is not well formed.
2. Prevent evaluation of '__apply_cv<Tp, Ret>' when 'Ret' is a function type.
'Ret' is a function type whenever 'Ret Tp::*' is a pointer to member function.
Attempting to add cv and ref qualifiers to a function type can cause a hard
compile error.
3. Remove the dummy overload __invoke(Rp Tp::*). It was present to help work
around #1. It will be replaced with a different '__invoke' overload that
represents a bad call to invoke.
After applying this patch the test func.wrap.func.inv/invoke.pass.cpp now
passes.
llvm-svn: 243370
This patch does a couple of things to get __invoke working for free-functions
and call objects.
1. Turn all uses of declval<Tp>() into declval<Tp&>(). The C++03 __invoke only
supports lvalues but it will be used when the compiler supports rvalue
references but not variadic templates. This change makes sure we don't
generate an rvalue.
2. Call objects for bullet 5 are now passed by reference and not value. Copying
the functor is incorrect. It will fail to compile for non-copyable functors
and it will discard cv-qualifiers on the call object, possibly leading to the
wrong function being called. I suspect that the reason the call object
was originally taken by value was to support temporary call objects.
However __invoke is only used internally and it is never given a temporary.
llvm-svn: 243368
This patch removes a large amount of duplicate code found in both
<__functional_base> and <__functional_base_03>. The only code that remains
in <__functional_base_03> is the C++03 implementation of __invoke and
__invoke_return.
llvm-svn: 242951
Summary:
The bug can be found here: http://llvm.org/bugs/show_bug.cgi?id=22468
`__invoke_void_return_wrapper` is needed to properly handle calling a function that returns a value but where the std::function return type is void. Without this '-Wsystem-headers' will cause `function::operator()(...)` to not compile.
Reviewers: eugenis, K-ballo, mclow.lists
Reviewed By: mclow.lists
Subscribers: cfe-commits
Differential Revision: http://reviews.llvm.org/D7444
llvm-svn: 228705
Eric Fiselier