From: Jason Merrill <jason@redhat.com>
Date: Fri, 16 Dec 2011 22:59:27 +0000 (-0500)
Subject: re PR c++/51331 (bad code generated when explicitly calling auto-generated constructo... 
X-Git-Tag: releases/gcc-4.6.3~255
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=78a8ed44d721a70e1fcebc72da9a9fec138a2fa1;p=thirdparty%2Fgcc.git

re PR c++/51331 (bad code generated when explicitly calling auto-generated constructor of virtual base)

	PR c++/51331
	* class.c (convert_to_base_statically): Just call
	build_simple_base_path.
	(build_simple_base_path): Check field offset.

From-SVN: r182418
---

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index a2fa74895b16..6260496830cc 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,10 @@
+2011-12-16  Jason Merrill  <jason@redhat.com>
+
+	PR c++/51331
+	* class.c (convert_to_base_statically): Just call
+	build_simple_base_path.
+	(build_simple_base_path): Check field offset.
+
 2011-12-14  Jason Merrill  <jason@redhat.com>
 
 	PR c++/51248
diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index 1c9a17b746a2..f14dd7804dc3 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -464,7 +464,14 @@ build_simple_base_path (tree expr, tree binfo)
     /* Is this the base field created by build_base_field?  */
     if (TREE_CODE (field) == FIELD_DECL
 	&& DECL_FIELD_IS_BASE (field)
-	&& TREE_TYPE (field) == type)
+	&& TREE_TYPE (field) == type
+	/* If we're looking for a field in the most-derived class,
+	   also check the field offset; we can have two base fields
+	   of the same type if one is an indirect virtual base and one
+	   is a direct non-virtual base.  */
+	&& (BINFO_INHERITANCE_CHAIN (d_binfo)
+	    || tree_int_cst_equal (byte_position (field),
+				   BINFO_OFFSET (binfo))))
       {
 	/* We don't use build_class_member_access_expr here, as that
 	   has unnecessary checks, and more importantly results in
@@ -541,6 +548,10 @@ convert_to_base_statically (tree expr, tree base)
     {
       tree pointer_type;
 
+      /* If this is a non-empty base, use a COMPONENT_REF.  */
+      if (!is_empty_class (BINFO_TYPE (base)))
+	return build_simple_base_path (expr, base);
+
       pointer_type = build_pointer_type (expr_type);
 
       /* We use fold_build2 and fold_convert below to simplify the trees
diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index f85a30b01fbe..14766b648fbc 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -141,7 +141,9 @@ initialize_vtbl_ptrs (tree addr)
    zero-initialization does not simply mean filling the storage with
    zero bytes.  FIELD_SIZE, if non-NULL, is the bit size of the field,
    subfields with bit positions at or above that bit size shouldn't
-   be added.  */
+   be added.  Note that this only works when the result is assigned
+   to a base COMPONENT_REF; if we only have a pointer to the base subobject,
+   expand_assignment will end up clearing the full size of TYPE.  */
 
 static tree
 build_zero_init_1 (tree type, tree nelts, bool static_storage_p,
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 0e3d1f662fc0..3bfeedb5a73a 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2011-12-16  Jason Merrill  <jason@redhat.com>
+
+	PR c++/51331
+	* g++.dg/init/value10.C: New.
+
 2011-12-15  H.J. Lu  <hongjiu.lu@intel.com>
 
 	Backport from mainline.
diff --git a/gcc/testsuite/g++.dg/init/value10.C b/gcc/testsuite/g++.dg/init/value10.C
new file mode 100644
index 000000000000..2066410a01d0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/init/value10.C
@@ -0,0 +1,27 @@
+// PR c++/51331
+// { dg-do run }
+
+struct A {
+  A(): x(10) {}
+  virtual ~A() {}
+
+  int x;
+};
+
+struct B: public virtual A {
+};
+
+struct C: public virtual A {
+};
+
+struct D: public B, virtual public C {
+  D(): B(), C() {}  // note an explicit call to C() which is auto-generated
+};
+
+int main() {
+  D* d = new D();
+
+  // Crashes here with the following message:
+  // *** glibc detected *** ./test: free(): invalid next size (fast)
+  delete d;
+}