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Implement P0033R1 - Re-enabling shared_from_this
Summary: See http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0033r1.html Reviewers: mclow.lists Subscribers: cfe-commits Differential Revision: http://reviews.llvm.org/D19254 llvm-svn: 271449
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@ -4120,7 +4120,7 @@ private:
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void
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__enable_weak_this(const enable_shared_from_this<_Yp>* __e) _NOEXCEPT
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{
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if (__e)
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if (__e && __e->__weak_this_.expired())
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{
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__e->__weak_this_.__ptr_ = const_cast<_Yp*>(static_cast<const _Yp*>(__e));
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__e->__weak_this_.__cntrl_ = __cntrl_;
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@ -5432,6 +5432,16 @@ public:
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shared_ptr<_Tp const> shared_from_this() const
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{return shared_ptr<const _Tp>(__weak_this_);}
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#if _LIBCPP_STD_VER > 14
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_LIBCPP_INLINE_VISIBILITY
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weak_ptr<_Tp> weak_from_this() _NOEXCEPT
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{ return __weak_this_; }
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_LIBCPP_INLINE_VISIBILITY
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weak_ptr<const _Tp> weak_from_this() const _NOEXCEPT
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{ return __weak_this_; }
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#endif // _LIBCPP_STD_VER > 14
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template <class _Up> friend class shared_ptr;
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};
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@ -18,11 +18,15 @@
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// public:
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// shared_ptr<T> shared_from_this();
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// shared_ptr<T const> shared_from_this() const;
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// weak_ptr<T> weak_from_this() noexcept; // C++17
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// weak_ptr<T const> weak_from_this() const noexecpt; // C++17
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// };
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#include <memory>
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#include <cassert>
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#include "test_macros.h"
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struct T
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: public std::enable_shared_from_this<T>
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{
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@ -32,6 +36,8 @@ struct Y : T {};
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struct Z : Y {};
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void nullDeleter(void*) {}
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int main()
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{
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{ // https://llvm.org/bugs/show_bug.cgi?id=18843
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@ -50,4 +56,84 @@ int main()
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assert(p == q);
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assert(!p.owner_before(q) && !q.owner_before(p)); // p and q share ownership
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}
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// Test LWG issue 2529. Only reset '__weak_ptr_' when it's already expired.
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// http://cplusplus.github.io/LWG/lwg-active.html#2529.
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// Test two different ways:
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// * Using 'weak_from_this().expired()' in C++17.
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// * Using 'shared_from_this()' in all dialects.
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{
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T* ptr = new T;
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std::shared_ptr<T> s(ptr);
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{
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// Don't re-initialize the "enabled_shared_from_this" base
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// because it already references a non-expired shared_ptr.
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std::shared_ptr<T> s2(ptr, &nullDeleter);
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}
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#if TEST_STD_VER > 14
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// The enabled_shared_from_this base should still be referencing
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// the original shared_ptr.
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assert(!ptr->weak_from_this().expired());
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#endif
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#ifndef TEST_HAS_NO_EXCEPTIONS
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{
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try {
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std::shared_ptr<T> new_s = ptr->shared_from_this();
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assert(new_s == s);
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} catch (std::bad_weak_ptr const&) {
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assert(false);
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} catch (...) {
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assert(false);
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}
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}
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#endif
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}
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// Test LWG issue 2529 again. This time check that an expired pointer
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// is replaced.
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{
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T* ptr = new T;
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std::weak_ptr<T> weak;
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{
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std::shared_ptr<T> s(ptr, &nullDeleter);
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assert(ptr->shared_from_this() == s);
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weak = s;
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assert(!weak.expired());
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}
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assert(weak.expired());
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weak.reset();
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#ifndef TEST_HAS_NO_EXCEPTIONS
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try {
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ptr->shared_from_this();
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assert(false);
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} catch (std::bad_weak_ptr const&) {
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} catch (...) { assert(false); }
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#endif
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{
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std::shared_ptr<T> s2(ptr, &nullDeleter);
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assert(ptr->shared_from_this() == s2);
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}
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delete ptr;
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}
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// Test weak_from_this_methods
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#if TEST_STD_VER > 14
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{
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T* ptr = new T;
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const T* cptr = ptr;
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static_assert(noexcept(ptr->weak_from_this()), "Operation must be noexcept");
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static_assert(noexcept(cptr->weak_from_this()), "Operation must be noexcept");
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std::weak_ptr<T> my_weak = ptr->weak_from_this();
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assert(my_weak.expired());
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std::weak_ptr<T const> my_const_weak = cptr->weak_from_this();
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assert(my_const_weak.expired());
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// Enable shared_from_this with ptr.
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std::shared_ptr<T> sptr(ptr);
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my_weak = ptr->weak_from_this();
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assert(!my_weak.expired());
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assert(my_weak.lock().get() == ptr);
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}
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#endif
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}
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@ -82,7 +82,7 @@
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<tr><td><a href="http://wg21.link/P0226R1">P0226R1</a></td><td>LWG</td><td>Mathematical Special Functions for C++17</td><td>Jacksonville</td><td></td><td></td></tr>
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<tr><td><a href="http://wg21.link/P0220R1">P0220R1</a></td><td>LWG</td><td>Adopt Library Fundamentals V1 TS Components for C++17</td><td>Jacksonville</td><td></td><td></td></tr>
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<tr><td><a href="http://wg21.link/P0218R1">P0218R1</a></td><td>LWG</td><td>Adopt the File System TS for C++17</td><td>Jacksonville</td><td></td><td></td></tr>
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<tr><td><a href="http://wg21.link/P0033R1">P0033R1</a></td><td>LWG</td><td>Re-enabling shared_from_this</td><td>Jacksonville</td><td></td><td></td></tr>
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<tr><td><a href="http://wg21.link/P0033R1">P0033R1</a></td><td>LWG</td><td>Re-enabling shared_from_this</td><td>Jacksonville</td><td>Complete</td><td>3.9</td></tr>
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<tr><td><a href="http://wg21.link/P0005R4">P0005R4</a></td><td>LWG</td><td>Adopt not_fn from Library Fundamentals 2 for C++17</td><td>Jacksonville</td><td></td><td></td></tr>
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<tr><td><a href="http://wg21.link/P0152R1">P0152R1</a></td><td>LWG</td><td>constexpr atomic::is_always_lock_free</td><td>Jacksonville</td><td>Complete</td><td>3.9</td></tr>
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<tr><td><a href="http://wg21.link/P0185R1">P0185R1</a></td><td>LWG</td><td>Adding [nothrow-]swappable traits</td><td>Jacksonville</td><td>Complete</td><td>3.9</td></tr>
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