re PR c/16351 (NULL dereference warnings)

gcc/ChangeLog:

2015-08-05  Manuel López-Ibáñez  <manu@gcc.gnu.org>
	    Jeff Law  <law@redhat.com>

	PR c/16351
	* doc/invoke.texi (Wnull-dereference): New.
	* tree-vrp.c (infer_value_range): Update call to infer_nonnull_range.
	* gimple-ssa-isolate-paths.c (find_implicit_erroneous_behaviour):
	Warn for potential NULL dereferences.
	(find_explicit_erroneous_behaviour): Warn for NULL dereferences.
	* ubsan.c (instrument_nonnull_arg): Call
	infer_nonnull_range_by_attribute.
	(instrument_nonnull_return): Likewise.
	* common.opt (Wnull-dereference); New.
	* gimple.c (infer_nonnull_range): Remove bool arguments.
	(infer_nonnull_range_by_dereference): New.
	(infer_nonnull_range_by_attribute): New.
	* gimple.h: Update declarations.

gcc/testsuite/ChangeLog:

2015-08-05  Manuel López-Ibáñez  <manu@gcc.gnu.org>
	    Jeff Law  <law@redhat.com>

	PR c/16351
	* gcc.dg/tree-ssa/isolate-2.c: Close comment.
	* gcc.dg/tree-ssa/isolate-4.c: Likewise.
	* gcc.dg/tree-ssa/wnull-dereference.c: New test.
	* gcc.dg/tree-ssa/isolate-1.c: Test warnings with -Wnull-dereference.
	* gcc.dg/tree-ssa/isolate-3.c: Likewise.
	* gcc.dg/tree-ssa/isolate-5.c: Likewise.



Co-Authored-By: Jeff Law <law@redhat.com>

From-SVN: r226640

1 files changed, 35 insertions, 19 deletions

diff --git a/gcc/gimple.c b/gcc/gimple.c
index 89291b0..e31a273 100644
--- a/gcc/gimple.c
+++ b/gcc/gimple.c
@@ -2618,16 +2618,20 @@ check_loadstore (gimple, tree op, tree, void *data)
   return false;
 }
 
-/* If OP can be inferred to be non-NULL after STMT executes, return true.
 
-   DEREFERENCE is TRUE if we can use a pointer dereference to infer a
-   non-NULL range, FALSE otherwise.
-
-   ATTRIBUTE is TRUE if we can use attributes to infer a non-NULL range
-   for function arguments and return values.  FALSE otherwise.  */
+/* Return true if OP can be inferred to be non-NULL after STMT executes,
+   either by using a pointer dereference or attributes.  */
+bool
+infer_nonnull_range (gimple stmt, tree op)
+{
+  return infer_nonnull_range_by_dereference (stmt, op)
+    || infer_nonnull_range_by_attribute (stmt, op);
+}
 
+/* Return true if OP can be inferred to be non-NULL after STMT
+   executes by using a pointer dereference.  */
 bool
-infer_nonnull_range (gimple stmt, tree op, bool dereference, bool attribute)
+infer_nonnull_range_by_dereference (gimple stmt, tree op)
 {
   /* We can only assume that a pointer dereference will yield
      non-NULL if -fdelete-null-pointer-checks is enabled.  */
@@ -2636,13 +2640,26 @@ infer_nonnull_range (gimple stmt, tree op, bool dereference, bool attribute)
       || gimple_code (stmt) == GIMPLE_ASM)
     return false;
 
-  if (dereference
-      && walk_stmt_load_store_ops (stmt, (void *)op,
-				   check_loadstore, check_loadstore))
+  if (walk_stmt_load_store_ops (stmt, (void *)op,
+				check_loadstore, check_loadstore))
     return true;
 
-  if (attribute
-      && is_gimple_call (stmt) && !gimple_call_internal_p (stmt))
+  return false;
+}
+
+/* Return true if OP can be inferred to be a non-NULL after STMT
+   executes by using attributes.  */
+bool
+infer_nonnull_range_by_attribute (gimple stmt, tree op)
+{
+  /* We can only assume that a pointer dereference will yield
+     non-NULL if -fdelete-null-pointer-checks is enabled.  */
+  if (!flag_delete_null_pointer_checks
+      || !POINTER_TYPE_P (TREE_TYPE (op))
+      || gimple_code (stmt) == GIMPLE_ASM)
+    return false;
+
+  if (is_gimple_call (stmt) && !gimple_call_internal_p (stmt))
     {
       tree fntype = gimple_call_fntype (stmt);
       tree attrs = TYPE_ATTRIBUTES (fntype);
@@ -2681,13 +2698,12 @@ infer_nonnull_range (gimple stmt, tree op, bool dereference, bool attribute)
 
   /* If this function is marked as returning non-null, then we can
      infer OP is non-null if it is used in the return statement.  */
-  if (attribute)
-    if (greturn *return_stmt = dyn_cast <greturn *> (stmt))
-      if (gimple_return_retval (return_stmt)
-	  && operand_equal_p (gimple_return_retval (return_stmt), op, 0)
-	  && lookup_attribute ("returns_nonnull",
-			       TYPE_ATTRIBUTES (TREE_TYPE (current_function_decl))))
-	return true;
+  if (greturn *return_stmt = dyn_cast <greturn *> (stmt))
+    if (gimple_return_retval (return_stmt)
+	&& operand_equal_p (gimple_return_retval (return_stmt), op, 0)
+	&& lookup_attribute ("returns_nonnull",
+			     TYPE_ATTRIBUTES (TREE_TYPE (current_function_decl))))
+      return true;
 
   return false;
 }