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C++ PATCH for c++/48873 (unnecessary dtor calls in new-expressions)
- From: Jason Merrill <jason at redhat dot com>
- To: gcc-patches List <gcc-patches at gcc dot gnu dot org>
- Date: Thu, 05 May 2011 10:53:21 -0400
- Subject: C++ PATCH for c++/48873 (unnecessary dtor calls in new-expressions)
Here the issue was that build_new_1 wants to stabilize any constructor
arguments so that the EH region for deleting the allocated memory can be
as small as possible. But stabilize_expr was being over-eager, making a
copy of a class with trivial constructors, but a non-trivial (and indeed
non-callable) destructor. And even if it didn't have a problematic
destructor, there's no reason to introduce extra copies of trivially
copyable classes. So this patch changes stabilize_expr to only make
copies of scalar types and class prvalues.
Tested x86_64-pc-linux-gnu, applying to trunk.
commit 21a411247eb5e59895aa54ff9a85e3cf8795a81a
Author: Jason Merrill <jason@redhat.com>
Date: Wed May 4 11:15:30 2011 -0400
PR c++/48873
* tree.c (stabilize_expr): Don't make gratuitous copies of classes.
diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index 0f2f86c..9a6e26d 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -3119,7 +3119,10 @@ stabilize_expr (tree exp, tree* initp)
if (!TREE_SIDE_EFFECTS (exp))
init_expr = NULL_TREE;
- else if (!TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (exp))
+ /* There are no expressions with REFERENCE_TYPE, but there can be call
+ arguments with such a type; just treat it as a pointer. */
+ else if (TREE_CODE (TREE_TYPE (exp)) == REFERENCE_TYPE
+ || SCALAR_TYPE_P (exp)
|| !lvalue_or_rvalue_with_address_p (exp))
{
init_expr = get_target_expr (exp);
diff --git a/gcc/testsuite/g++.dg/init/new32.C b/gcc/testsuite/g++.dg/init/new32.C
new file mode 100644
index 0000000..f827857
--- /dev/null
+++ b/gcc/testsuite/g++.dg/init/new32.C
@@ -0,0 +1,16 @@
+// PR c++/48873
+
+#include <new>
+
+struct D {
+private:
+ ~D();
+};
+
+template<class T>
+T& create();
+
+void f()
+{
+ D* dp = new (((void*) 0)) D(create<D>()); // #
+}