Summary:
`std::move` and `std::forward` were not marked constexpr in C++11. This can be very damaging because it makes otherwise constant expressions non-constant. For example:
```
#include <utility>
template <class T>
struct Foo {
constexpr Foo(T&& tx) : t(std::move(tx)) {}
T t;
};
[[clang::require_constant_initialization]] Foo<int> f(42); // Foo should be constant initialized but C++11 move is not constexpr. As a result `f` is an unsafe global.
```
This patch applies `constexpr` to `move` and `forward` as an extension in C++11. Normally the library is not allowed to add `constexpr` because it may be observable to the user. In particular adding constexpr may cause valid code to stop compiling. However these problems only happen in more complex situations, like making `__invoke(...)` constexpr. `forward` and `move` are simply enough that applying `constexpr` is safe.
Note that libstdc++ has offered this extension since at least 4.8.1.
Most of the changes in this patch are simply test cleanups or additions. The main changes in the tests are:
* Fold all `forward_N.fail.cpp` tests into a single `forward.fail.cpp` test using -verify.
* Delete most `move_only_N.fail.cpp` tests because they weren't actually testing anything.
* Fold `move_copy.pass.cpp` and `move_only.pass.cpp` into a single `move.pass.cpp` test.
* Add return type and noexcept tests for `forward` and `move`.
Reviewers: rsmith, mclow.lists, EricWF
Subscribers: K-ballo, loladiro
Differential Revision: https://reviews.llvm.org/D24637
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@282439 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
Libc++ still uses per-feature configuration macros when configuring for C++11. However libc++ requires a feature-complete C++11 compiler so there is no reason to check individual features. This patch starts the process of removing the feature specific macros and replacing their usage with `_LIBCPP_CXX03_LANG`.
This patch removes the __config macros:
* _LIBCPP_HAS_NO_TRAILING_RETURN
* _LIBCPP_HAS_NO_TEMPLATE_ALIASES
* _LIBCPP_HAS_NO_ADVANCED_SFINAE
* _LIBCPP_HAS_NO_DEFAULT_FUNCTION_TEMPLATE_ARGS
* _LIBCPP_HAS_NO_STATIC_ASSERT
As a drive I also changed our C++03 static_assert to use _Static_assert if available.
I plan to commit this without review if nobody voices an objection.
Reviewers: mclow.lists
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D24895
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@282347 91177308-0d34-0410-b5e6-96231b3b80d8
This assignment operator was previously broken since the SFINAE always resulted
in substitution failure. This caused assignments to turn into
copy construction + assignment.
This patch was originally committed as r279953 but was reverted due to warnings
in the test-suite. This new patch corrects those warnings.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@279955 91177308-0d34-0410-b5e6-96231b3b80d8
The test emits warnings causing the test-suite to fail. Since I want this
patch merged into 3.9 I'll recommit it with a clean test.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@279954 91177308-0d34-0410-b5e6-96231b3b80d8
This assignment operator was previously broken since the SFINAE always resulted
in substitution failure. This caused assignments to turn into
copy construction + assignment.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@279953 91177308-0d34-0410-b5e6-96231b3b80d8
I think I've solved issues with is_assignable and references to incomplete
types. The updated patch adds tests for this case.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@276603 91177308-0d34-0410-b5e6-96231b3b80d8
This is a breaking change. The SFINAE required is instantiated the second
the class is instantiated, and this can cause hard SFINAE errors
when applied to references to incomplete types. Ex.
struct IncompleteType;
extern IncompleteType it;
std::tuple<IncompleteType&> t(it); // SFINAE will blow up.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@276598 91177308-0d34-0410-b5e6-96231b3b80d8
In C++03 mode evaluating the SFINAE can cause a hard error due to
access control violations. This is a problem because the SFINAE
is evaluated as soon as the class is instantiated, and not later.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@276594 91177308-0d34-0410-b5e6-96231b3b80d8
The test I originally checked in only worked with ToT Clang. This patch
updates the test so that it works as far back as 3.5.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@276093 91177308-0d34-0410-b5e6-96231b3b80d8
There is a bug in Clang's __is_constructible builtin that causes it
to return true for function types; ex [T = void()].
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@276092 91177308-0d34-0410-b5e6-96231b3b80d8
The previous implementation relied highly on specializations to handle
special cases. This new implementation lets the compiler do the work when possible.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@276084 91177308-0d34-0410-b5e6-96231b3b80d8
This patch upgrades <tuple> to be C++17 compliant by implementing:
* tuple_size_v: This was forgotten when implementing the other _v traits.
* std::apply: This was added via LFTS v1 in p0220r1.
* std::make_from_tuple: This was added in p0209r2.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@275745 91177308-0d34-0410-b5e6-96231b3b80d8
