Rewrite variant, also PR libstdc++/85517

* include/std/variant (__do_visit): New.
(__variant_cast): Likewise.
(__variant_cookie): Likewise.
(__erased_*): Remove.
(_Variant_storage::_S_vtable): Likewise.
(_Variant_storage::__M_reset_impl): Adjust to use __do_visit.
(_Variant_storage::__M_reset): Adjust.
(__variant_construct): New.
(_Copy_ctor_base(const _Copy_ctor_base&)): Adjust to use
__variant_construct.
(_Move_ctor_base(_Move_ctor_base&&)): Likewise.
(_Move_ctor_base::__M_destructive_copy): New.
(_Move_ctor_base::__M_destructive_move): Adjust to use
__variant_construct.
(_Copy_assign_base::operator=): Adjust to use __do_visit.
(_Copy_assign_alias): Adjust to check both copy assignment
and copy construction for triviality.
(_Move_assign_base::operator=): Adjust to use __do_visit.
(_Multi_array): Add support for visitors that accept and return
a __variant_cookie.
(__gen_vtable_impl::_S_apply_all_alts): Likewise.
(__gen_vtable_impl::_S_apply_single_alt): Likewise.
(__gen_vtable_impl::__element_by_index_or_cookie): New. Generate
a __variant_cookie temporary for a variant that is valueless and..
(__gen_vtable_impl::__visit_invoke): ..adjust here.
(__gen_vtable::_Array_type): Conditionally make space for
the __variant_cookie visitor case.
(__variant_construct_by_index): New.
(get_if): Adjust to use std::addressof.
(relops): Adjust to use __do_visit.
(variant): Add __variant_cast and __variant_construct_by_index
as friends.
(variant::emplace): Use _M_reset() and __variant_construct_by_index
instead of self-destruction.
(variant::swap): Adjust to use __do_visit.
(visit): Reimplement in terms of __do_visit.
(__variant_hash_call_base_impl::operator()): Adjust to use __do_visit.
* testsuite/20_util/variant/compile.cc: Adjust.
* testsuite/20_util/variant/run.cc: Likewise.

From-SVN: r269422

libstdc++-v3/ChangeLog

+2019-03-06  Ville Voutilainen  <ville.voutilainen@gmail.com>
+
+	Rewrite variant.
+	Also PR libstdc++/85517
+	* include/std/variant (__do_visit): New.
+	(__variant_cast): Likewise.
+	(__variant_cookie): Likewise.
+	(__erased_*): Remove.
+	(_Variant_storage::_S_vtable): Likewise.
+	(_Variant_storage::__M_reset_impl): Adjust to use __do_visit.
+	(_Variant_storage::__M_reset): Adjust.
+	(__variant_construct): New.
+	(_Copy_ctor_base(const _Copy_ctor_base&)): Adjust to use
+	__variant_construct.
+	(_Move_ctor_base(_Move_ctor_base&&)): Likewise.
+	(_Move_ctor_base::__M_destructive_copy): New.
+	(_Move_ctor_base::__M_destructive_move): Adjust to use
+	__variant_construct.
+	(_Copy_assign_base::operator=): Adjust to use __do_visit.
+	(_Copy_assign_alias): Adjust to check both copy assignment
+	and copy construction for triviality.
+	(_Move_assign_base::operator=): Adjust to use __do_visit.
+	(_Multi_array): Add support for visitors that accept and return
+	a __variant_cookie.
+	(__gen_vtable_impl::_S_apply_all_alts): Likewise.
+	(__gen_vtable_impl::_S_apply_single_alt): Likewise.
+	(__gen_vtable_impl::__element_by_index_or_cookie): New. Generate
+	a __variant_cookie temporary for a variant that is valueless and..
+	(__gen_vtable_impl::__visit_invoke): ..adjust here.
+	(__gen_vtable::_Array_type): Conditionally make space for
+	the __variant_cookie visitor case.
+	(__variant_construct_by_index): New.
+	(get_if): Adjust to use std::addressof.
+	(relops): Adjust to use __do_visit.
+	(variant): Add __variant_cast and __variant_construct_by_index
+	as friends.
+	(variant::emplace): Use _M_reset() and __variant_construct_by_index
+	instead of self-destruction.
+	(variant::swap): Adjust to use __do_visit.
+	(visit): Reimplement in terms of __do_visit.
+	(__variant_hash_call_base_impl::operator()): Adjust to use __do_visit.
+	* testsuite/20_util/variant/compile.cc: Adjust.
+	* testsuite/20_util/variant/run.cc: Likewise.
+
 2019-03-06  Jonathan Wakely  <jwakely@redhat.com>
 
 	* include/bits/c++config.h (_cpp_lib_char8_t): Add L suffix to

libstdc++-v3/testsuite/20_util/variant/compile.cc

@@ -488,12 +488,12 @@ void test_triviality()
   TEST_TEMPLATE(=default, =default,         , =default,         ,  true, false,  true, false)
   TEST_TEMPLATE(=default, =default,         ,         , =default,  true, false, false,  true)
   TEST_TEMPLATE(=default, =default,         ,         ,         ,  true, false, false, false)
-  TEST_TEMPLATE(=default,         , =default, =default, =default, false,  true,  true,  true)
-  TEST_TEMPLATE(=default,         , =default, =default,         , false,  true,  true, false)
+  TEST_TEMPLATE(=default,         , =default, =default, =default, false,  true,  false,  true)
+  TEST_TEMPLATE(=default,         , =default, =default,         , false,  true,  false, false)
   TEST_TEMPLATE(=default,         , =default,         , =default, false,  true, false,  true)
   TEST_TEMPLATE(=default,         , =default,         ,         , false,  true, false, false)
-  TEST_TEMPLATE(=default,         ,         , =default, =default, false, false,  true,  true)
-  TEST_TEMPLATE(=default,         ,         , =default,         , false, false,  true, false)
+  TEST_TEMPLATE(=default,         ,         , =default, =default, false, false,  false,  true)
+  TEST_TEMPLATE(=default,         ,         , =default,         , false, false,  false, false)
   TEST_TEMPLATE(=default,         ,         ,         , =default, false, false, false,  true)
   TEST_TEMPLATE(=default,         ,         ,         ,         , false, false, false, false)
   TEST_TEMPLATE(        , =default, =default, =default, =default, false, false, false, false)

libstdc++-v3/testsuite/20_util/variant/run.cc

@@ -88,6 +88,21 @@ void arbitrary_ctor()
   VERIFY(get<1>(v) == "a");
 }
 
+struct ThrowingMoveCtorThrowsCopyCtor
+{
+  ThrowingMoveCtorThrowsCopyCtor() noexcept = default;
+  ThrowingMoveCtorThrowsCopyCtor(ThrowingMoveCtorThrowsCopyCtor&&) {}
+  ThrowingMoveCtorThrowsCopyCtor(ThrowingMoveCtorThrowsCopyCtor const&)
+  {
+    throw 0;
+  }
+
+  ThrowingMoveCtorThrowsCopyCtor& operator=(ThrowingMoveCtorThrowsCopyCtor&&) noexcept
+    = default;
+  ThrowingMoveCtorThrowsCopyCtor& operator=(ThrowingMoveCtorThrowsCopyCtor const&) noexcept
+    = default;
+};
+
 void copy_assign()
 {
   variant<monostate, string> v("a");
@@ -96,6 +111,20 @@ void copy_assign()
   u = v;
   VERIFY(holds_alternative<string>(u));
   VERIFY(get<string>(u) == "a");
+  {
+    std::variant<int, ThrowingMoveCtorThrowsCopyCtor> v1,
+      v2 = ThrowingMoveCtorThrowsCopyCtor();
+    bool should_throw = false;
+    try
+      {
+	v1 = v2;
+      }
+    catch(int)
+      {
+	should_throw = true;
+      }
+    VERIFY(should_throw);
+  }
 }
 
 void move_assign()
@@ -183,11 +212,15 @@ void emplace()
     AlwaysThrow a;
     try { v.emplace<1>(a); } catch (nullptr_t) { }
     VERIFY(v.valueless_by_exception());
+    v.emplace<0>(42);
+    VERIFY(!v.valueless_by_exception());
   }
   {
     variant<int, AlwaysThrow> v;
     try { v.emplace<1>(AlwaysThrow{}); } catch (nullptr_t) { }
     VERIFY(v.valueless_by_exception());
+    v.emplace<0>(42);
+    VERIFY(!v.valueless_by_exception());
   }
   VERIFY(&v.emplace<0>(1) == &std::get<0>(v));
   VERIFY(&v.emplace<int>(1) == &std::get<int>(v));
@@ -258,6 +291,7 @@ void test_relational()
     VERIFY(v < w);
     VERIFY(v <= w);
     VERIFY(!(v == w));
+    VERIFY(v == v);
     VERIFY(v != w);
     VERIFY(w > v);
     VERIFY(w >= v);