On 1/30/23 16:36, Patrick Palka wrote:
Here we're crashing from check_bases_and_members due to
CLASSTYPE_DESTRUCTOR being an OVERLOAD which, due to the pruning
performed by add_method, should only happen if there is no viable
destructor or the destructor is ambiguous.
This patch fixes this by making check_bases_and_members naturally handle
CLASSTYPE_DESTRUCTOR being an OVERLOAD. It's then convenient to prune
the OVERLOAD after diagnosing the inevitable OR failure in check_methods.
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk and perhaps 12?
OK for trunk, this doesn't seem important to backport.
PR c++/96745
gcc/cp/ChangeLog:
* class.cc (check_methods): Diagnose an unviable OVERLOAD
set for CLASSTYPE_DESTRUCTOR differently from an ambiguous one.
Then prune the OVERLOAD to a single function.
(check_bases_and_members): Handle CLASSTYPE_DESTRUCTOR being
an OVERLOAD when calling deduce_noexcept_on_destructor.
Document why it has to be called before check_methods.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-dtor1.C: New test.
---
gcc/cp/class.cc | 22 ++++++++++++++++++---
gcc/testsuite/g++.dg/cpp2a/concepts-dtor1.C | 18 +++++++++++++++++
2 files changed, 37 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-dtor1.C
diff --git a/gcc/cp/class.cc b/gcc/cp/class.cc
index d3ce8532d56..c6878cba2ae 100644
--- a/gcc/cp/class.cc
+++ b/gcc/cp/class.cc
@@ -4808,9 +4808,23 @@ check_methods (tree t)
in that class with an empty argument list to select the destructor
for the class, also known as the selected destructor. The program
is ill-formed if overload resolution fails. */
+ int viable = 0;
+ for (tree fn : ovl_range (dtor))
+ if (constraints_satisfied_p (fn))
+ ++viable;
+ gcc_checking_assert (viable != 1);
+
auto_diagnostic_group d;
- error_at (location_of (t), "destructor for %qT is ambiguous", t);
+ if (viable == 0)
+ error_at (location_of (t), "no viable destructor for %qT", t);
+ else
+ error_at (location_of (t), "destructor for %qT is ambiguous", t);
print_candidates (dtor);
+
+ /* Arbitrarily prune the overload set to a single function for
+ sake of error recovery. */
+ tree *slot = find_member_slot (t, dtor_identifier);
+ *slot = get_first_fn (dtor);
}
else if (user_provided_p (dtor))
TYPE_HAS_NONTRIVIAL_DESTRUCTOR (t) = true;
@@ -6048,10 +6062,12 @@ check_bases_and_members (tree t)
check_bases (t, &cant_have_const_ctor, &no_const_asn_ref);
/* Deduce noexcept on destructor. This needs to happen after we've set
- triviality flags appropriately for our bases. */
+ triviality flags appropriately for our bases, and before checking
+ overriden virtual functions via check_methods. */
if (cxx_dialect >= cxx11)
if (tree dtor = CLASSTYPE_DESTRUCTOR (t))
- deduce_noexcept_on_destructor (dtor);
+ for (tree fn : ovl_range (dtor))
+ deduce_noexcept_on_destructor (fn);
/* Check all the method declarations. */
check_methods (t);
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-dtor1.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-dtor1.C
new file mode 100644
index 00000000000..b1f3b4e579f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-dtor1.C
@@ -0,0 +1,18 @@
+// PR c++/96745
+// { dg-do compile { target c++20 } }
+
+template<class T>
+struct A { // { dg-error "destructor for 'A<int>' is ambiguous" }
+ ~A() requires true;
+ ~A() requires (!!true);
+};
+
+A<int> a;
+
+template<class T>
+struct B { // { dg-error "no viable destructor for 'B<int>'" }
+ ~B() requires false;
+ ~B() requires (!!false);
+};
+
+B<int> b;
