re PR c++/13009 (Implicitly-defined assignment operator writes to wrong memory)

PR c++/13009
	* call.c (build_special_member_call): Do not assume that we have a
	pointer to the complete object in an assignment operator.

	PR c++/13009
	* g++.dg/init/assign1.C: New test.

From-SVN: r75189

gcc/cp/ChangeLog

@@ -1,3 +1,9 @@
+2003-12-28  Mark Mitchell  <mark@codesourcery.com>
+
+	PR c++/13009
+	* call.c (build_special_member_call): Do not assume that we have a
+	pointer to the complete object in an assignment operator.
+
 2003-12-28  Roger Sayle  <roger@eyesopen.com>
 
 	PR c++/13070

gcc/cp/call.c

@@ -4865,14 +4865,23 @@ build_special_member_call (tree instance, tree name, tree args,
 	  || name == deleting_dtor_identifier)
 	my_friendly_assert (args == NULL_TREE, 20020712);
 
-      /* We must perform the conversion here so that we do not
-	 subsequently check to see whether BINFO is an accessible
-	 base.  (It is OK for a constructor to call a constructor in
-	 an inaccessible base as long as the constructor being called
-	 is accessible.)  */
+      /* Convert to the base class, if necessary.  */
       if (!same_type_ignoring_top_level_qualifiers_p 
 	  (TREE_TYPE (instance), BINFO_TYPE (binfo)))
-	instance = convert_to_base_statically (instance, binfo);
+	{
+	  if (name != ansi_assopname (NOP_EXPR))
+	    /* For constructors and destructors, either the base is
+	       non-virtual, or it is virtual but we are doing the
+	       conversion from a constructor or destructor for the
+	       complete object.  In either case, we can convert
+	       statically.  */
+	    instance = convert_to_base_statically (instance, binfo);
+	  else
+	    /* However, for assignment operators, we must convert
+	       dynamically if the base is virtual.  */
+	    instance = build_base_path (PLUS_EXPR, instance,
+					binfo, /*nonnull=*/1);
+	}
     }
   
   my_friendly_assert (instance != NULL_TREE, 20020712);

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2003-12-28  Mark Mitchell  <mark@codesourcery.com>
+
+	PR c++/13009
+	* g++.dg/init/assign1.C: New test.
+
 2003-12-28  Roger Sayle  <roger@eyesopen.com>
 
 	PR c++/13070

gcc/testsuite/g++.dg/init/assign1.C

@@ -0,0 +1,30 @@
+// PR c++/13009
+// { dg-do run }
+
+struct A {
+  char a;
+};
+
+struct B: public virtual A {
+  #if 0 // this piece of code works around the problem
+  B& operator= (const B& other)
+  {
+    A::operator= (other);
+  }
+  #endif
+};
+
+struct C: public B {
+  char c;
+};
+
+int main() {
+  B b;
+  b.a = 'b';
+  C c;
+  c.a = c.c = 'c';
+  
+  c.B::operator= (b);
+  if (c.a != 'b' || c.c != 'c')
+    return 1;
+}