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C++ PATCH for c++/47999 (incorrect auto deduction in template)
- From: Jason Merrill <jason at redhat dot com>
- To: gcc-patches List <gcc-patches at gcc dot gnu dot org>
- Date: Wed, 16 Mar 2011 12:23:37 -0400
- Subject: C++ PATCH for c++/47999 (incorrect auto deduction in template)
In templates, we do overload resolution and then throw away most of it,
going back to the pre-conversion arguments. But when the call returns a
reference, we shouldn't elide the dereference and pretend it returns by
value, as that confuses lvalue_p.
Tested x86_64-pc-linux-gnu, applying to trunk.
commit 79330512f8ade4ecff47ab8cb8c050440d9648e0
Author: Jason Merrill <jason@redhat.com>
Date: Tue Mar 8 08:46:41 2011 -0500
PR c++/47999
* semantics.c (finish_call_expr): Preserve reference semantics
in templates.
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 53497f3..ce24d46 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -2150,11 +2150,17 @@ finish_call_expr (tree fn, VEC(tree,gc) **args, bool disallow_virtual,
/* A call where the function is unknown. */
result = cp_build_function_call_vec (fn, args, complain);
- if (processing_template_decl)
+ if (processing_template_decl && result != error_mark_node)
{
+ if (TREE_CODE (result) == INDIRECT_REF)
+ result = TREE_OPERAND (result, 0);
+ gcc_assert (TREE_CODE (result) == CALL_EXPR
+ || TREE_CODE (fn) == PSEUDO_DTOR_EXPR
+ || errorcount);
result = build_call_vec (TREE_TYPE (result), orig_fn, orig_args);
KOENIG_LOOKUP_P (result) = koenig_p;
release_tree_vector (orig_args);
+ result = convert_from_reference (result);
}
return result;
diff --git a/gcc/testsuite/g++.dg/cpp0x/auto22.C b/gcc/testsuite/g++.dg/cpp0x/auto22.C
new file mode 100644
index 0000000..66630e5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/auto22.C
@@ -0,0 +1,21 @@
+// PR c++/47999
+// { dg-options -std=c++0x }
+
+int& identity(int& i)
+{
+ return i;
+}
+
+// In a function template, auto type deduction works incorrectly.
+template <typename = void>
+void f()
+{
+ int i = 0;
+ auto&& x = identity(i); // Type of x should be `int&`, but it is `int&&`.
+}
+
+int main (int argc, char* argv[])
+{
+ f();
+ return 0;
+}