[gcc r13-7471] c++: init-list of uncopyable type [PR110102]

[gcc r13-7471] c++: init-list of uncopyable type [PR110102]

[Jason Merrill]

https://gcc.gnu.org/g:be1e122bd20c17aa0b57fc40cbd64f9e9a889aa2

commit r13-7471-gbe1e122bd20c17aa0b57fc40cbd64f9e9a889aa2
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Jun 8 16:21:38 2023 -0400

    c++: init-list of uncopyable type [PR110102]
    
    The maybe_init_list_as_range optimization is a form of copy elision, but we
    can only elide well-formed copies.
    
            PR c++/110102
    
    gcc/cp/ChangeLog:
    
            * call.cc (maybe_init_list_as_array): Check that the element type is
            copyable.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp0x/initlist-opt1.C: New test.

Diff:
---
 gcc/cp/call.cc                             |  8 ++++++++
 gcc/testsuite/g++.dg/cpp0x/initlist-opt1.C | 15 +++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index 867d7a5bee6..6dc925ecc5b 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -4271,6 +4271,14 @@ maybe_init_list_as_array (tree elttype, tree init)
   if (has_non_trivial_temporaries (first))
     return NULL_TREE;
 
+  /* We can't do this if copying from the initializer_list would be
+     ill-formed.  */
+  tree copy_argtypes = make_tree_vec (1);
+  TREE_VEC_ELT (copy_argtypes, 0)
+    = cp_build_qualified_type (elttype, TYPE_QUAL_CONST);
+  if (!is_xible (INIT_EXPR, elttype, copy_argtypes))
+    return NULL_TREE;
+
   init_elttype = cp_build_qualified_type (init_elttype, TYPE_QUAL_CONST);
   tree arr = build_array_of_n_type (init_elttype, CONSTRUCTOR_NELTS (init));
   return finish_compound_literal (arr, init, tf_none);
diff --git a/gcc/testsuite/g++.dg/cpp0x/initlist-opt1.C b/gcc/testsuite/g++.dg/cpp0x/initlist-opt1.C
new file mode 100644
index 00000000000..56de4bc0092
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/initlist-opt1.C
@@ -0,0 +1,15 @@
+// PR c++/110102
+// { dg-do compile { target c++11 } }
+
+// { dg-error "deleted|construct_at" "" { target *-*-* } 0 }
+
+#include <list>
+
+struct A {
+  A(int) {}
+  A(const A&) = delete;		// { dg-message "declared here" }
+  A(A&&) {}
+};
+int main() {
+  std::list<A> v = {1,2,3};
+}