[pushed] c++: anonymous union member reference [PR105452]

[Jason Merrill <jason@redhat.com>]

Tested x86_64-pc-linux-gnu, applying to trunk.

-- 8< --

While parsing the anonymous union, we don't yet know that it's an anonymous
union, so we build the reference to 'v' in the static_assert relative to the
union type.  But at instantiation time we know it's an anonymous union, so
we need to avoid trying to check access for 'v' in the union again; the
simplest approach seemed to be to make accessible_p step out to the
containing class.

While looking at this I also noticed that we were having trouble with DMI in
an anonymous union referring to members of the containing class; there
we just need to give current_class_ptr the right type.

	PR c++/105452

gcc/cp/ChangeLog:

	* search.cc (type_context_for_name_lookup): New.
	(accessible_p): Handle anonymous union.
	* init.cc (maybe_instantiate_nsdmi_init): Use
	type_context_for_name_lookup.
	* parser.cc (cp_parser_class_specifier): Likewise.
	* cp-tree.h (type_context_for_name_lookup): Declare.

gcc/testsuite/ChangeLog:

	* g++.dg/lookup/anon8.C: New test.
---
 gcc/cp/cp-tree.h                    |  1 +
 gcc/cp/init.cc                      |  2 +-
 gcc/cp/parser.cc                    |  5 +++--
 gcc/cp/search.cc                    | 23 +++++++++++++++++++++++
 gcc/testsuite/g++.dg/lookup/anon8.C | 16 ++++++++++++++++
 5 files changed, 44 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/lookup/anon8.C

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 0e37d4043d0..d450b3d5b78 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7534,6 +7534,7 @@ extern int at_function_scope_p			(void);
 extern bool at_class_scope_p			(void);
 extern bool at_namespace_scope_p		(void);
 extern tree context_for_name_lookup		(tree);
+extern tree type_context_for_name_lookup	(tree);
 extern tree lookup_conversions			(tree);
 extern tree binfo_from_vbase			(tree);
 extern tree binfo_for_vbase			(tree, tree);
diff --git a/gcc/cp/init.cc b/gcc/cp/init.cc
index c5a55dae563..9571d18170e 100644
--- a/gcc/cp/init.cc
+++ b/gcc/cp/init.cc
@@ -597,7 +597,7 @@ maybe_instantiate_nsdmi_init (tree member, tsubst_flags_t complain)
 	  DECL_INSTANTIATING_NSDMI_P (member) = 1;
 
 	  bool pushed = false;
-	  tree ctx = DECL_CONTEXT (member);
+	  tree ctx = type_context_for_name_lookup (member);
 
 	  processing_template_decl_sentinel ptds (/*reset*/false);
 	  if (!currently_open_class (ctx))
diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index e8efc32f2c2..a6341b98af2 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -26439,11 +26439,12 @@ cp_parser_class_specifier (cp_parser* parser)
       /* Now parse any NSDMIs.  */
       FOR_EACH_VEC_SAFE_ELT (unparsed_nsdmis, ix, decl)
 	{
-	  if (class_type != DECL_CONTEXT (decl))
+	  tree ctx = type_context_for_name_lookup (decl);
+	  if (class_type != ctx)
 	    {
 	      if (pushed_scope)
 		pop_scope (pushed_scope);
-	      class_type = DECL_CONTEXT (decl);
+	      class_type = ctx;
 	      pushed_scope = push_scope (class_type);
 	    }
 	  inject_this_parameter (class_type, TYPE_UNQUALIFIED);
diff --git a/gcc/cp/search.cc b/gcc/cp/search.cc
index e472a97679d..3f521b3bd72 100644
--- a/gcc/cp/search.cc
+++ b/gcc/cp/search.cc
@@ -485,6 +485,25 @@ context_for_name_lookup (tree decl)
   return context;
 }
 
+/* Like the above, but always return a type, because it's simpler for member
+   handling to refer to the anonymous aggr rather than a function.  */
+
+tree
+type_context_for_name_lookup (tree decl)
+{
+  tree context = DECL_P (decl) ? DECL_CONTEXT (decl) : decl;
+  gcc_checking_assert (CLASS_TYPE_P (context));
+
+  while (context && TYPE_P (context) && ANON_AGGR_TYPE_P (context))
+    {
+      tree next = TYPE_CONTEXT (context);
+      if (!TYPE_P (next))
+	break;
+      context = next;
+    }
+  return context;
+}
+
 /* Returns true iff DECL is declared in TYPE.  */
 
 static bool
@@ -881,6 +900,10 @@ accessible_p (tree type, tree decl, bool consider_local_p)
   else
     otype = type;
 
+  /* Anonymous unions don't have their own access.  */
+  if (ANON_AGGR_TYPE_P (type))
+    type = type_context_for_name_lookup (type);
+
   /* [class.access.base]
 
      A member m is accessible when named in class N if
diff --git a/gcc/testsuite/g++.dg/lookup/anon8.C b/gcc/testsuite/g++.dg/lookup/anon8.C
new file mode 100644
index 00000000000..80124caba63
--- /dev/null
+++ b/gcc/testsuite/g++.dg/lookup/anon8.C
@@ -0,0 +1,16 @@
+// PR c++/105452
+// { dg-do compile { target c++11 } }
+
+template <typename T>
+struct C {
+  int i = 42;
+  union {
+    T v = i;
+    static_assert(sizeof(v) == sizeof(char), "");
+  };
+};
+
+int main() {
+  C<char> x;
+  return x.v;
+}

base-commit: a23b33a1bdeff7bc2289d9ebb7cb7b7ec0a605f5
prerequisite-patch-id: a099996174aa44b595d914cbadf18d39bfbf2afa
-- 
2.31.1