PR c++/84850 - -Wclass-memaccess on a memcpy in a copy assignment ope…

…rator with no nontrivial bases or members

gcc/cp/ChangeLog:

	PR c++/84850
	* call.c (first_non_public_field): New template and function.
	(first_non_trivial_field): New function.
	(maybe_warn_class_memaccess): Call them.

gcc/testsuite/ChangeLog:

	PR c++/84850
	* g++.dg/Wclass-memaccess-3.C: New test.
	* g++.dg/Wclass-memaccess-4.C: New test.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@258719 138bc75d-0d04-0410-961f-82ee72b054a4

gcc/cp/ChangeLog

@@ -1,3 +1,10 @@
+2018-03-21  Martin Sebor  <[email protected]>
+
+	PR c++/84850
+	* call.c (first_non_public_field): New template and function.
+	(first_non_trivial_field): New function.
+	(maybe_warn_class_memaccess): Call them.
+
 2018-03-21  David Malcolm  <[email protected]>
 
 	PR c++/84892

gcc/cp/call.c

@@ -8261,13 +8261,17 @@ build_over_call (struct z_candidate *cand, int flags, tsubst_flags_t complain)
   return call;
 }
 
-/* Return the DECL of the first non-public data member of class TYPE
-   or null if none can be found.  */
+namespace
+{
 
-static tree
-first_non_public_field (tree type)
+/* Return the DECL of the first non-static subobject of class TYPE
+   that satisfies the predicate PRED or null if none can be found.  */
+
+template <class Predicate>
+tree
+first_non_static_field (tree type, Predicate pred)
 {
-  if (!CLASS_TYPE_P (type))
+  if (!type || !CLASS_TYPE_P (type))
     return NULL_TREE;
 
   for (tree field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field))
@@ -8276,7 +8280,7 @@ first_non_public_field (tree type)
 	continue;
       if (TREE_STATIC (field))
 	continue;
-      if (TREE_PRIVATE (field) || TREE_PROTECTED (field))
+      if (pred (field))
 	return field;
     }
 
@@ -8286,14 +8290,51 @@ first_non_public_field (tree type)
        BINFO_BASE_ITERATE (binfo, i, base_binfo); i++)
     {
       tree base = TREE_TYPE (base_binfo);
-
-      if (tree field = first_non_public_field (base))
+      if (pred (base))
+	return base;
+      if (tree field = first_non_static_field (base, pred))
 	return field;
     }
 
   return NULL_TREE;
 }
 
+struct NonPublicField
+{
+  bool operator() (const_tree t)
+  {
+    return DECL_P (t) && (TREE_PRIVATE (t) || TREE_PROTECTED (t));
+  }
+};
+
+/* Return the DECL of the first non-public subobject of class TYPE
+   or null if none can be found.  */
+
+static inline tree
+first_non_public_field (tree type)
+{
+  return first_non_static_field (type, NonPublicField ());
+}
+
+struct NonTrivialField
+{
+  bool operator() (const_tree t)
+  {
+    return !trivial_type_p (DECL_P (t) ? TREE_TYPE (t) : t);
+  }
+};
+
+/* Return the DECL of the first non-trivial subobject of class TYPE
+   or null if none can be found.  */
+
+static inline tree
+first_non_trivial_field (tree type)
+{
+  return first_non_static_field (type, NonTrivialField ());
+}
+
+}   /* unnamed namespace */
+
 /* Return true if all copy and move assignment operator overloads for
    class TYPE are trivial and at least one of them is not deleted and,
    when ACCESS is set, accessible.  Return false otherwise.  Set
@@ -8419,22 +8460,30 @@ maybe_warn_class_memaccess (location_t loc, tree fndecl,
   if (!desttype || !COMPLETE_TYPE_P (desttype) || !CLASS_TYPE_P (desttype))
     return;
 
-  /* Check to see if the raw memory call is made by a ctor or dtor
-     with this as the destination argument for the destination type.
-     If so, be more permissive.  */
+  /* Check to see if the raw memory call is made by a non-static member
+     function with THIS as the destination argument for the destination
+     type.  If so, and if the class has no non-trivial bases or members,
+     be more permissive.  */
   if (current_function_decl
-      && (DECL_CONSTRUCTOR_P (current_function_decl)
-	  || DECL_DESTRUCTOR_P (current_function_decl))
+      && DECL_NONSTATIC_MEMBER_FUNCTION_P (current_function_decl)
       && is_this_parameter (tree_strip_nop_conversions (dest)))
     {
       tree ctx = DECL_CONTEXT (current_function_decl);
       bool special = same_type_ignoring_top_level_qualifiers_p (ctx, desttype);
-
       tree binfo = TYPE_BINFO (ctx);
 
-      /* A ctor and dtor for a class with no bases and no virtual functions
-	 can do whatever they want.  Bail early with no further checking.  */
-      if (special && !BINFO_VTABLE (binfo) && !BINFO_N_BASE_BINFOS (binfo))
+      /* FIXME: The following if statement is overly permissive (see
+	 bug 84851).  Remove it in GCC 9.  */
+      if (special
+	  && !BINFO_VTABLE (binfo)
+	  && !BINFO_N_BASE_BINFOS (binfo)
+	  && (DECL_CONSTRUCTOR_P (current_function_decl)
+	      || DECL_DESTRUCTOR_P (current_function_decl)))
+	return;
+
+      if (special
+	  && !BINFO_VTABLE (binfo)
+	  && !first_non_trivial_field (desttype))
 	return;
     }
 

gcc/testsuite/ChangeLog

@@ -1,3 +1,9 @@
+2018-03-21  Martin Sebor  <[email protected]>
+
+	PR c++/84850
+	* g++.dg/Wclass-memaccess-3.C: New test.
+	* g++.dg/Wclass-memaccess-4.C: New test.
+
 2018-03-21  David Malcolm  <[email protected]>
 
 	PR c++/84892