re PR c++/42844 (const variable requires initializer / no explicitly declared default constructor)

	PR c++/42844
	* decl.c (check_for_uninitialized_const_var): Handle classes that need
	constructing, too.
	(check_initializer): Call it for classes that need constructing, too.
	* class.c (in_class_defaulted_default_constructor): New.
	* cp-tree.h: Declare it.

Co-Authored-By: Jason Merrill <jason@redhat.com>

From-SVN: r158797

4 files changed, 66 insertions, 7 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 6dec7c3..a996461 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,13 @@
+2010-04-27  Fabien Chêne  <fabien.chene@gmail.com>
+	    Jason Merrill  <jason@redhat.com>
+
+	PR c++/42844
+	* decl.c (check_for_uninitialized_const_var): Handle classes that need
+	constructing, too.
+	(check_initializer): Call it for classes that need constructing, too.
+	* class.c (in_class_defaulted_default_constructor): New.
+	* cp-tree.h: Declare it.
+
 2010-04-20  Jason Merrill  <jason@redhat.com>
 
 	PR c++/9335
diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index 1bab07d..26da21b 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -1,6 +1,6 @@
 /* Functions related to building classes and their related objects.
    Copyright (C) 1987, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
-   1999, 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009
+   1999, 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010
    Free Software Foundation, Inc.
    Contributed by Michael Tiemann (tiemann@cygnus.com)
 
@@ -4177,6 +4177,34 @@ type_has_user_nondefault_constructor (tree t)
   return false;
 }
 
+/* Returns the defaulted constructor if T has one. Otherwise, returns
+   NULL_TREE.  */
+
+tree
+in_class_defaulted_default_constructor (tree t)
+{
+  tree fns, args;
+
+  if (!TYPE_HAS_USER_CONSTRUCTOR (t))
+    return NULL_TREE;
+
+  for (fns = CLASSTYPE_CONSTRUCTORS (t); fns; fns = OVL_NEXT (fns))
+    {
+      tree fn = OVL_CURRENT (fns);
+
+      if (DECL_DEFAULTED_IN_CLASS_P (fn))
+	{
+	  args = FUNCTION_FIRST_USER_PARMTYPE (fn);
+	  while (args && TREE_PURPOSE (args))
+	    args = TREE_CHAIN (args);
+	  if (!args || args == void_list_node)
+	    return fn;
+	}
+    }
+
+  return NULL_TREE;
+}
+
 /* Returns true iff FN is a user-provided function, i.e. user-declared
    and not defaulted at its first declaration; or explicit, private,
    protected, or non-const.  */
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 26059046..a7ed134 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -4611,6 +4611,7 @@ extern void check_for_override			(tree, tree);
 extern void push_class_stack			(void);
 extern void pop_class_stack			(void);
 extern bool type_has_user_nondefault_constructor (tree);
+extern tree in_class_defaulted_default_constructor (tree);
 extern bool user_provided_p			(tree);
 extern bool type_has_user_provided_constructor  (tree);
 extern bool type_has_user_provided_default_constructor (tree);
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 580f6f8..346b7b4 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -1,6 +1,6 @@
 /* Process declarations and variables for C++ compiler.
    Copyright (C) 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
-   2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
+   2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
    Free Software Foundation, Inc.
    Contributed by Michael Tiemann (tiemann@cygnus.com)
 
@@ -4692,7 +4692,7 @@ maybe_commonize_var (tree decl)
 static void
 check_for_uninitialized_const_var (tree decl)
 {
-  tree type = TREE_TYPE (decl);
+  tree type = strip_array_types (TREE_TYPE (decl));
 
   if (TREE_CODE (decl) == VAR_DECL && DECL_DECLARED_CONSTEXPR_P (decl)
       && DECL_INITIAL (decl) == NULL)
@@ -4704,11 +4704,28 @@ check_for_uninitialized_const_var (tree decl)
   else if (TREE_CODE (decl) == VAR_DECL
       && TREE_CODE (type) != REFERENCE_TYPE
       && CP_TYPE_CONST_P (type)
-      && !TYPE_NEEDS_CONSTRUCTING (type)
+      && (!TYPE_NEEDS_CONSTRUCTING (type)
+	  || !type_has_user_provided_default_constructor (type))
       && !DECL_INITIAL (decl))
-    error ("uninitialized const %qD", decl);
-}
+    {
+      permerror (DECL_SOURCE_LOCATION (decl),
+		 "uninitialized const %qD", decl);
 
+      if (CLASS_TYPE_P (type)
+	  && !type_has_user_provided_default_constructor (type))
+	{
+	  tree defaulted_ctor;
+
+	  inform (DECL_SOURCE_LOCATION (TYPE_MAIN_DECL (type)),
+		  "%q#T has no user-provided default constructor", type);
+	  defaulted_ctor = in_class_defaulted_default_constructor (type);
+	  if (defaulted_ctor)
+	    inform (DECL_SOURCE_LOCATION (defaulted_ctor),
+		    "constructor is not user-provided because it is "
+		    "explicitly defaulted in the class body");
+	}
+    }
+}
 
 /* Structure holding the current initializer being processed by reshape_init.
    CUR is a pointer to the current element being processed, END is a pointer
@@ -5261,7 +5278,10 @@ check_initializer (tree decl, tree init, int flags, tree *cleanup)
   else if (DECL_EXTERNAL (decl))
     ;
   else if (TYPE_P (type) && TYPE_NEEDS_CONSTRUCTING (type))
-    return build_aggr_init_full_exprs (decl, init, flags);
+    {
+      check_for_uninitialized_const_var (decl);
+      return build_aggr_init_full_exprs (decl, init, flags);
+    }
   else if (MAYBE_CLASS_TYPE_P (type))
     {
       tree core_type = strip_array_types (type);