re PR sanitizer/81275 (-fsanitize=thread produce incorrect -Wreturn-type warning)

	PR sanitizer/81275
	* tree.c (block_may_fallthru): Return false if SWITCH_ALL_CASES_P
	is set on SWITCH_EXPR and !block_may_fallthru (SWITCH_BODY ()).
c/
	* c-typeck.c (c_finish_case): Set SWITCH_ALL_CASES_P if
	c_switch_covers_all_cases_p returns true.
c-family/
	* c-common.c (c_switch_covers_all_cases_p_1,
	c_switch_covers_all_cases_p): New functions.
	* c-common.h (c_switch_covers_all_cases_p): Declare.
testsuite/
	* c-c++-common/tsan/pr81275.c: New test.

From-SVN: r255217

3 files changed, 66 insertions, 0 deletions

diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index ce966bb..abbcb90 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,3 +1,10 @@
+2017-11-28  Jakub Jelinek  <jakub@redhat.com>
+
+	PR sanitizer/81275
+	* c-common.c (c_switch_covers_all_cases_p_1,
+	c_switch_covers_all_cases_p): New functions.
+	* c-common.h (c_switch_covers_all_cases_p): Declare.
+
 2017-11-28  Julia Koval  <julia.koval@intel.com>
             Sebastian Peryt  <sebastian.peryt@intel.com>
 
diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 82561657..1d79aee 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -4898,6 +4898,64 @@ c_add_case_label (location_t loc, splay_tree cases, tree cond, tree orig_type,
   return error_mark_node;
 }
 
+/* Subroutine of c_switch_covers_all_cases_p, called via
+   splay_tree_foreach.  Return 1 if it doesn't cover all the cases.
+   ARGS[0] is initially NULL and after the first iteration is the
+   so far highest case label.  ARGS[1] is the minimum of SWITCH_COND's
+   type.  */
+
+static int
+c_switch_covers_all_cases_p_1 (splay_tree_node node, void *data)
+{
+  tree label = (tree) node->value;
+  tree *args = (tree *) data;
+
+  /* If there is a default case, we shouldn't have called this.  */
+  gcc_assert (CASE_LOW (label));
+
+  if (args[0] == NULL_TREE)
+    {
+      if (wi::to_widest (args[1]) < wi::to_widest (CASE_LOW (label)))
+	return 1;
+    }
+  else if (wi::add (wi::to_widest (args[0]), 1)
+	   != wi::to_widest (CASE_LOW (label)))
+    return 1;
+  if (CASE_HIGH (label))
+    args[0] = CASE_HIGH (label);
+  else
+    args[0] = CASE_LOW (label);
+  return 0;
+}
+
+/* Return true if switch with CASES and switch condition with type
+   covers all possible values in the case labels.  */
+
+bool
+c_switch_covers_all_cases_p (splay_tree cases, tree type)
+{
+  /* If there is default:, this is always the case.  */
+  splay_tree_node default_node
+    = splay_tree_lookup (cases, (splay_tree_key) NULL);
+  if (default_node)
+    return true;
+
+  if (!INTEGRAL_TYPE_P (type))
+    return false;
+
+  tree args[2] = { NULL_TREE, TYPE_MIN_VALUE (type) };
+  if (splay_tree_foreach (cases, c_switch_covers_all_cases_p_1, args))
+    return false;
+
+  /* If there are no cases at all, or if the highest case label
+     is smaller than TYPE_MAX_VALUE, return false.  */
+  if (args[0] == NULL_TREE
+      || wi::to_widest (args[0]) < wi::to_widest (TYPE_MAX_VALUE (type)))
+    return false;
+
+  return true;
+}
+
 /* Finish an expression taking the address of LABEL (an
    IDENTIFIER_NODE).  Returns an expression for the address.
 
diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index 5e55e5e..7561531 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -969,6 +969,7 @@ extern int case_compare (splay_tree_key, splay_tree_key);
 
 extern tree c_add_case_label (location_t, splay_tree, tree, tree, tree, tree,
 			      bool *);
+extern bool c_switch_covers_all_cases_p (splay_tree, tree);
 
 extern tree build_function_call (location_t, tree, tree);