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* [gcc r12-8799] c++: fix triviality of class with unsatisfied op=
@ 2022-09-29 20:11 Jason Merrill
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From: Jason Merrill @ 2022-09-29 20:11 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:aeba3e009b0abfccaf01797556445dbf891cc8dc
commit r12-8799-gaeba3e009b0abfccaf01797556445dbf891cc8dc
Author: Jason Merrill <jason@redhat.com>
Date: Thu Sep 29 13:45:02 2022 -0400
c++: fix triviality of class with unsatisfied op=
cxx20_pair is trivially copyable because it has a trivial copy constructor
and only a deleted copy assignment operator; the non-triviality of the
unsatisfied copy assignment overload is not considered.
gcc/cp/ChangeLog:
* class.cc (check_methods): Call constraints_satisfied_p.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/cond-triv3.C: New test.
Diff:
---
gcc/cp/class.cc | 13 ++++++++--
gcc/testsuite/g++.dg/cpp2a/cond-triv3.C | 44 +++++++++++++++++++++++++++++++++
2 files changed, 55 insertions(+), 2 deletions(-)
diff --git a/gcc/cp/class.cc b/gcc/cp/class.cc
index bfda0065bf4..b9e0a77f52b 100644
--- a/gcc/cp/class.cc
+++ b/gcc/cp/class.cc
@@ -4780,8 +4780,9 @@ check_methods (tree t)
/* Check whether the eligible special member functions (P0848) are
user-provided. add_method arranged that the CLASSTYPE_MEMBER_VEC only
- has the eligible ones; TYPE_FIELDS also contains ineligible overloads,
- which is why this needs to be separate from the loop above. */
+ has the eligible ones, unless none are eligible; TYPE_FIELDS also contains
+ ineligible overloads, which is why this needs to be separate from the loop
+ above. */
if (tree dtor = CLASSTYPE_DESTRUCTOR (t))
{
@@ -4804,6 +4805,10 @@ check_methods (tree t)
{
if (!user_provided_p (fn))
/* Might be trivial. */;
+ else if (TREE_CODE (fn) == TEMPLATE_DECL)
+ /* Templates are never special members. */;
+ else if (!constraints_satisfied_p (fn))
+ /* Not eligible. */;
else if (copy_fn_p (fn))
TYPE_HAS_COMPLEX_COPY_CTOR (t) = true;
else if (move_fn_p (fn))
@@ -4814,6 +4819,10 @@ check_methods (tree t)
{
if (!user_provided_p (fn))
/* Might be trivial. */;
+ else if (TREE_CODE (fn) == TEMPLATE_DECL)
+ /* Templates are never special members. */;
+ else if (!constraints_satisfied_p (fn))
+ /* Not eligible. */;
else if (copy_fn_p (fn))
TYPE_HAS_COMPLEX_COPY_ASSIGN (t) = true;
else if (move_fn_p (fn))
diff --git a/gcc/testsuite/g++.dg/cpp2a/cond-triv3.C b/gcc/testsuite/g++.dg/cpp2a/cond-triv3.C
new file mode 100644
index 00000000000..d0711cf2607
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/cond-triv3.C
@@ -0,0 +1,44 @@
+// { dg-do compile { target c++20 } }
+
+template<class T>
+struct X
+{
+ T first{};
+
+ X& operator=(const X&) = delete;
+ X& operator=(const X&) requires requires (T& t) { t = t; } { return *this; }
+};
+
+// C++20 std::pair<const int, int>:
+using cxx20_pair = X<const int>;
+static_assert( __is_trivially_constructible(cxx20_pair, const cxx20_pair&), "" );
+static_assert( !__is_assignable(cxx20_pair&, const cxx20_pair&), "" );
+static_assert( __is_trivially_copyable(cxx20_pair), "" );
+
+template<bool, typename, typename F> struct conditional { using type = F; };
+template<typename T, typename F> struct conditional<true, T, F> { using type = T; };
+
+struct base
+{
+ base() = default;
+ ~base() = default;
+ base(const base&) = default;
+ base& operator=(const base&) = delete;
+};
+
+struct nope;
+
+template<class T>
+struct Y : base
+{
+ T first{};
+
+ Y& operator=(typename conditional<__is_assignable(T&, const T&), const Y&, const nope&>::type)
+ { return *this; }
+};
+
+// C++17 std::pair<const int, int>:
+using cxx17_pair = Y<const int>;
+static_assert( __is_trivially_constructible(cxx17_pair, const cxx17_pair&), "" );
+static_assert( ! __is_assignable(cxx17_pair&, const cxx17_pair&), "" );
+static_assert( __is_trivially_copyable(cxx17_pair), "???" );
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