re PR c++/55993 ([C++11] derived-to-base conversion fails in constant expression)

	PR c++/55993
	* semantics.c (cxx_fold_indirect_ref): Handle empty bases at
	non-zero offsets, too.

From-SVN: r196023

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index ddd0aa0..977d245 100644 (file)
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,9 @@
 2013-02-13  Jason Merrill  <jason@redhat.com>
 
+       PR c++/55993
+       * semantics.c (cxx_fold_indirect_ref): Handle empty bases at
+       non-zero offsets, too.
+
        PR c++/56155
        * decl.c (build_enumerator): Always convert the value to a
        fixed underlying type.

diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 3415828..30c8c52 100644 (file)
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -7448,6 +7448,15 @@ cxx_fold_indirect_ref (location_t loc, tree type, tree op0, bool *empty_base)
              return build4_loc (loc, ARRAY_REF, type, op00, op01,
                                 NULL_TREE, NULL_TREE);
            }
+         /* Also handle conversion to an empty base class, which
+            is represented with a NOP_EXPR.  */
+         else if (is_empty_class (type)
+                  && CLASS_TYPE_P (op00type)
+                  && DERIVED_FROM_P (type, op00type))
+           {
+             *empty_base = true;
+             return op00;
+           }
          /* ((foo *)&struct_with_foo_field)[1] => COMPONENT_REF */
          else if (RECORD_OR_UNION_TYPE_P (op00type))
            {

diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-empty6.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-empty6.C
new file mode 100644 (file)
index 0000000..be9a6c6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-empty6.C
@@ -0,0 +1,11 @@
+// PR c++/55993
+// { dg-do compile { target c++11 } }
+
+struct A {};
+struct B:A {};
+struct C:A {};
+struct D:B,C {};
+
+constexpr D d {};
+constexpr const C& e=d; // OK
+constexpr auto f=static_cast<const C&>(d); // FAIL