c++: Properly detect calls to digest_init in build_vec_init [PR114619]

We currently ICE in checking mode with cxx_dialect < 17 on the following
valid code

=== cut here ===
struct X {
  X(const X&) {}
};
extern X x;
void foo () {
  new X[1]{x};
}
=== cut here ===

We trip on a gcc_checking_assert in cp_gimplify_expr due to a
TARGET_EXPR that is not TARGET_EXPR_ELIDING_P. As pointed by Jason, the
problem is that build_vec_init does not recognize that digest_init has
been called, and we end up calling the copy constructor twice.

This happens because the detection in build_vec_init assumes that BASE
is a reference to the array, while it's a pointer to its first element
here. This patch makes sure that the detection works in both cases.

	PR c++/114619

gcc/cp/ChangeLog:

	* init.cc (build_vec_init): Properly determine whether
	digest_init has been called.

gcc/testsuite/ChangeLog:

	* g++.dg/init/no-elide4.C: New test.

diff --git a/gcc/cp/init.cc b/gcc/cp/init.cc
index 3ab7f96335c9ae5596a07a603b1637163e8e47f3..613775c5a7c821c9ddd08c507a248264d803e1fa 100644 (file)
--- a/gcc/cp/init.cc
+++ b/gcc/cp/init.cc
@@ -4786,7 +4786,8 @@ build_vec_init (tree base, tree maxindex, tree init,
       tree field, elt;
       /* If the constructor already has the array type, it's been through
         digest_init, so we shouldn't try to do anything more.  */
-      bool digested = same_type_p (atype, TREE_TYPE (init));
+      bool digested = (TREE_CODE (TREE_TYPE (init)) == ARRAY_TYPE
+                      && same_type_p (type, TREE_TYPE (TREE_TYPE (init))));
       from_array = 0;
 
       if (length_check)

diff --git a/gcc/testsuite/g++.dg/init/no-elide4.C b/gcc/testsuite/g++.dg/init/no-elide4.C
new file mode 100644 (file)
index 0000000..9377d9f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/init/no-elide4.C
@@ -0,0 +1,11 @@
+// PR c++/114619
+// { dg-do "compile" { target c++11 } }
+// { dg-options "-fno-elide-constructors" }
+
+struct X {
+  X(const X&) {}
+};
+extern X x;
+void foo () {
+  new X[1]{x};
+}