re PR c++/69922 (Bogus -Wnonnull-compare for: ... ? static_cast<T*>(this) : nullptr)

	PR c++/69922
	* class.c (build_base_path): Set TREE_NO_WARNING on the null_test.
	Avoid folding it.
	* init.c (build_vec_delete_1, build_delete): Don't fold the non-NULL
	tests.
	* cp-gimplify.c (cp_fold): For TREE_NO_WARNING comparisons with NULL,
	unless they are folded into INTEGER_CST, error_mark_node or some
	comparison with NULL, avoid folding them and use either the original
	comparison or non-folded comparison of folded arguments.
	* cp-ubsan.c (cp_ubsan_instrument_vptr): Set TREE_NO_WARNING on the
	comparison, don't fold the comparison right away.

	* g++.dg/warn/Wnonnull-compare-6.C: New test.
	* g++.dg/warn/Wnonnull-compare-7.C: New test.
	* g++.dg/ubsan/pr69922.C: New test.

From-SVN: r233684

9 files changed, 110 insertions, 18 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 897c28f..28a3168 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,17 @@
+2016-02-24  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/69922
+	* class.c (build_base_path): Set TREE_NO_WARNING on the null_test.
+	Avoid folding it.
+	* init.c (build_vec_delete_1, build_delete): Don't fold the non-NULL
+	tests.
+	* cp-gimplify.c (cp_fold): For TREE_NO_WARNING comparisons with NULL,
+	unless they are folded into INTEGER_CST, error_mark_node or some
+	comparison with NULL, avoid folding them and use either the original
+	comparison or non-folded comparison of folded arguments.
+	* cp-ubsan.c (cp_ubsan_instrument_vptr): Set TREE_NO_WARNING on the
+	comparison, don't fold the comparison right away.
+
 2016-02-24  Jason Merrill  <jason@redhat.com>
 
 	PR c++/69323
diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index b705d6b..f6ad696 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -392,8 +392,11 @@ build_base_path (enum tree_code code,
   if (null_test)
     {
       tree zero = cp_convert (TREE_TYPE (expr), nullptr_node, complain);
-      null_test = fold_build2_loc (input_location, NE_EXPR, boolean_type_node,
-			       expr, zero);
+      null_test = build2_loc (input_location, NE_EXPR, boolean_type_node,
+			      expr, zero);
+      /* This is a compiler generated comparison, don't emit
+	 e.g. -Wnonnull-compare warning for it.  */
+      TREE_NO_WARNING (null_test) = 1;
     }
 
   /* If this is a simple base reference, express it as a COMPONENT_REF.  */
diff --git a/gcc/cp/cp-gimplify.c b/gcc/cp/cp-gimplify.c
index c59cd90..a77b242 100644
--- a/gcc/cp/cp-gimplify.c
+++ b/gcc/cp/cp-gimplify.c
@@ -2069,8 +2069,24 @@ cp_fold (tree x)
 	x = fold (x);
 
       if (TREE_NO_WARNING (org_x)
-	  && TREE_CODE (x) == TREE_CODE (org_x))
-	TREE_NO_WARNING (x) = 1;
+	  && warn_nonnull_compare
+	  && COMPARISON_CLASS_P (org_x))
+	{
+	  if (x == error_mark_node || TREE_CODE (x) == INTEGER_CST)
+	    ;
+	  else if (COMPARISON_CLASS_P (x))
+	    TREE_NO_WARNING (x) = 1;
+	  /* Otherwise give up on optimizing these, let GIMPLE folders
+	     optimize those later on.  */
+	  else if (op0 != TREE_OPERAND (org_x, 0)
+		   || op1 != TREE_OPERAND (org_x, 1))
+	    {
+	      x = build2_loc (loc, code, TREE_TYPE (org_x), op0, op1);
+	      TREE_NO_WARNING (x) = 1;
+	    }
+	  else
+	    x = org_x;
+	}
       break;
 
     case VEC_COND_EXPR:
diff --git a/gcc/cp/cp-ubsan.c b/gcc/cp/cp-ubsan.c
index 7454c0a..a5aefcf 100644
--- a/gcc/cp/cp-ubsan.c
+++ b/gcc/cp/cp-ubsan.c
@@ -70,10 +70,15 @@ cp_ubsan_instrument_vptr (location_t loc, tree op, tree type, bool is_addr,
   vptr = fold_convert_loc (loc, pointer_sized_int_node, vptr);
   vptr = fold_convert_loc (loc, uint64_type_node, vptr);
   if (ckind == UBSAN_DOWNCAST_POINTER)
-    vptr = fold_build3 (COND_EXPR, uint64_type_node,
-			fold_build2 (NE_EXPR, boolean_type_node, op,
-				     build_zero_cst (TREE_TYPE (op))),
-			vptr, build_int_cst (uint64_type_node, 0));
+    {
+      tree cond = build2_loc (loc, NE_EXPR, boolean_type_node, op,
+			      build_zero_cst (TREE_TYPE (op)));
+      /* This is a compiler generated comparison, don't emit
+	 e.g. -Wnonnull-compare warning for it.  */
+      TREE_NO_WARNING (cond) = 1;
+      vptr = build3_loc (loc, COND_EXPR, uint64_type_node, cond,
+			 vptr, build_int_cst (uint64_type_node, 0));
+    }
   tree ti_decl = get_tinfo_decl (type);
   mark_used (ti_decl);
   tree ptype = build_pointer_type (type);
diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index 19279e3..43f854c4 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -3678,15 +3678,13 @@ build_vec_delete_1 (tree base, tree maxindex, tree type,
     body = integer_zero_node;
 
   /* Outermost wrapper: If pointer is null, punt.  */
-  tree cond
-    = fold_build2_loc (input_location, NE_EXPR, boolean_type_node, base,
-		       fold_convert (TREE_TYPE (base), nullptr_node));
+  tree cond = build2_loc (input_location, NE_EXPR, boolean_type_node, base,
+			  fold_convert (TREE_TYPE (base), nullptr_node));
   /* This is a compiler generated comparison, don't emit
      e.g. -Wnonnull-compare warning for it.  */
-  if (TREE_CODE (cond) == NE_EXPR)
-    TREE_NO_WARNING (cond) = 1;
-  body = fold_build3_loc (input_location, COND_EXPR, void_type_node,
-			  cond, body, integer_zero_node);
+  TREE_NO_WARNING (cond) = 1;
+  body = build3_loc (input_location, COND_EXPR, void_type_node,
+		     cond, body, integer_zero_node);
   body = build1 (NOP_EXPR, void_type_node, body);
 
   if (controller)
@@ -4523,9 +4521,8 @@ build_delete (tree otype, tree addr, special_function_kind auto_delete,
 	{
 	  /* Handle deleting a null pointer.  */
 	  warning_sentinel s (warn_address);
-	  ifexp = fold (cp_build_binary_op (input_location,
-					    NE_EXPR, addr, nullptr_node,
-					    complain));
+	  ifexp = cp_build_binary_op (input_location, NE_EXPR, addr,
+				      nullptr_node, complain);
 	  if (ifexp == error_mark_node)
 	    return error_mark_node;
 	  /* This is a compiler generated comparison, don't emit
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 4ba14fc..e5cfd9a 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,10 @@
+2016-02-24  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/69922
+	* g++.dg/warn/Wnonnull-compare-6.C: New test.
+	* g++.dg/warn/Wnonnull-compare-7.C: New test.
+	* g++.dg/ubsan/pr69922.C: New test.
+
 2016-02-24  Marek Polacek  <polacek@redhat.com>
 
 	PR c/69819
diff --git a/gcc/testsuite/g++.dg/ubsan/pr69922.C b/gcc/testsuite/g++.dg/ubsan/pr69922.C
new file mode 100644
index 0000000..0392750
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ubsan/pr69922.C
@@ -0,0 +1,18 @@
+// PR c++/69922
+// { dg-do compile }
+// { dg-options "-fsanitize=vptr -Wnonnull-compare" }
+
+struct S { virtual ~S (); };
+struct T : S { T *bar (); T *baz (); T *q; bool b; };
+
+T *
+T::bar ()
+{
+  return static_cast<T*>(reinterpret_cast<S*>(this));	// { dg-bogus "nonnull argument" }
+}
+
+T *
+T::baz ()
+{
+  return static_cast<T*>(reinterpret_cast<S*>(b ? this : q));	// { dg-bogus "nonnull argument" }
+}
diff --git a/gcc/testsuite/g++.dg/warn/Wnonnull-compare-6.C b/gcc/testsuite/g++.dg/warn/Wnonnull-compare-6.C
new file mode 100644
index 0000000..d327df9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wnonnull-compare-6.C
@@ -0,0 +1,13 @@
+// PR c++/69922
+// { dg-do compile }
+// { dg-options "-Wnonnull-compare" }
+
+struct T { virtual ~T (); };
+struct S { virtual ~S (); T *f (bool); };
+struct U : S, T {};
+
+T *
+S::f (bool b)
+{
+  return b ? static_cast<U *> (this) : (U *) 0;	// { dg-bogus "nonnull argument" }
+}
diff --git a/gcc/testsuite/g++.dg/warn/Wnonnull-compare-7.C b/gcc/testsuite/g++.dg/warn/Wnonnull-compare-7.C
new file mode 100644
index 0000000..6c19a43
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wnonnull-compare-7.C
@@ -0,0 +1,19 @@
+// PR c++/69922
+// { dg-do compile }
+// { dg-options "-Wnonnull-compare" }
+
+struct S { virtual ~S (); };
+struct T { virtual ~T (); };
+bool b, c;
+S *p;
+T *q, *r;
+
+S::~S ()
+{
+  delete (b ? this : p);		// { dg-bogus "nonnull argument" }
+}
+
+T::~T ()
+{
+  delete (b ? (c ? this : q) : r);	// { dg-bogus "nonnull argument" }
+}