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

	PR sanitizer/81275
	* cp-tree.h (SWITCH_STMT_ALL_CASES_P): Define.
	(SWITCH_STMT_NO_BREAK_P): Define.
	(note_break_stmt, note_iteration_stmt_body_start,
	note_iteration_stmt_body_end): Declare.
	* decl.c (struct cp_switch): Add has_default_p, break_stmt_seen_p
	and in_loop_body_p fields. 
	(push_switch): Clear them.
	(pop_switch): Set SWITCH_STMT_CANNOT_FALLTHRU_P if has_default_p
	and !break_stmt_seen_p.  Assert in_loop_body_p is false.
	(note_break_stmt, note_iteration_stmt_body_start,
	note_iteration_stmt_body_end): New functions.
	(finish_case_label): Set has_default_p when both low and high
	are NULL_TREE.
	* parser.c (cp_parser_iteration_statement): Use
	note_iteration_stmt_body_start and note_iteration_stmt_body_end
	around parsing iteration body.
	* pt.c (tsubst_expr): Likewise.
	* cp-objcp-common.c (cxx_block_may_fallthru): Return false for
	SWITCH_STMT which contains no BREAK_STMTs, contains a default:
	CASE_LABEL_EXPR and where SWITCH_STMT_BODY isn't empty and
	can't fallthru.
	* semantics.c (finish_break_stmt): Call note_break_stmt.
	* cp-gimplify.c (genericize_switch_stmt): Copy SWITCH_STMT_ALL_CASES_P
	bit to SWITCH_ALL_CASES_P.  Assert that if SWITCH_STMT_NO_BREAK_P then
	the break label is not TREE_USED.

	* g++.dg/warn/pr81275-1.C: New test.
	* g++.dg/warn/pr81275-2.C: New test.
	* g++.dg/warn/pr81275-3.C: New test.
	* c-c++-common/tsan/pr81275.c: Skip for C++ and -O2.

From-SVN: r255218

1 files changed, 57 insertions, 0 deletions

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 9f557b8..7085d5a 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -3426,6 +3426,13 @@ struct cp_switch
   /* Remember whether there was a case value that is outside the
      range of the original type of the controlling expression.  */
   bool outside_range_p;
+  /* Remember whether a default: case label has been seen.  */
+  bool has_default_p;
+  /* Remember whether a BREAK_STMT has been seen in this SWITCH_STMT.  */
+  bool break_stmt_seen_p;
+  /* Set if inside of {FOR,DO,WHILE}_BODY nested inside of a switch,
+     where BREAK_STMT doesn't belong to the SWITCH_STMT.  */
+  bool in_loop_body_p;
 };
 
 /* A stack of the currently active switch statements.  The innermost
@@ -3448,6 +3455,9 @@ push_switch (tree switch_stmt)
   p->switch_stmt = switch_stmt;
   p->cases = splay_tree_new (case_compare, NULL, NULL);
   p->outside_range_p = false;
+  p->has_default_p = false;
+  p->break_stmt_seen_p = false;
+  p->in_loop_body_p = false;
   switch_stack = p;
 }
 
@@ -3468,11 +3478,55 @@ pop_switch (void)
 			  SWITCH_STMT_COND (cs->switch_stmt),
 			  bool_cond_p, cs->outside_range_p);
 
+  /* For the benefit of block_may_fallthru remember if the switch body
+     case labels cover all possible values and if there are break; stmts.  */
+  if (cs->has_default_p
+      || (!processing_template_decl
+	  && c_switch_covers_all_cases_p (cs->cases,
+					  SWITCH_STMT_TYPE (cs->switch_stmt))))
+    SWITCH_STMT_ALL_CASES_P (cs->switch_stmt) = 1;
+  if (!cs->break_stmt_seen_p)
+    SWITCH_STMT_NO_BREAK_P (cs->switch_stmt) = 1;
+  gcc_assert (!cs->in_loop_body_p);
   splay_tree_delete (cs->cases);
   switch_stack = switch_stack->next;
   free (cs);
 }
 
+/* Note that a BREAK_STMT is about to be added.  If it is inside of
+   a SWITCH_STMT and not inside of a loop body inside of it, note
+   in switch_stack we've seen a BREAK_STMT.  */
+
+void
+note_break_stmt (void)
+{
+  if (switch_stack && !switch_stack->in_loop_body_p)
+    switch_stack->break_stmt_seen_p = true;
+}
+
+/* Note the start of processing of an iteration statement's body.
+   The note_break_stmt function will do nothing while processing it.
+   Return a flag that should be passed to note_iteration_stmt_body_end.  */
+
+bool
+note_iteration_stmt_body_start (void)
+{
+  if (!switch_stack)
+    return false;
+  bool ret = switch_stack->in_loop_body_p;
+  switch_stack->in_loop_body_p = true;
+  return ret;
+}
+
+/* Note the end of processing of an iteration statement's body.  */
+
+void
+note_iteration_stmt_body_end (bool prev)
+{
+  if (switch_stack)
+    switch_stack->in_loop_body_p = prev;
+}
+
 /* Convert a case constant VALUE in a switch to the type TYPE of the switch
    condition.  Note that if TYPE and VALUE are already integral we don't
    really do the conversion because the language-independent
@@ -3507,6 +3561,9 @@ finish_case_label (location_t loc, tree low_value, tree high_value)
   cp_binding_level *p;
   tree type;
 
+  if (low_value == NULL_TREE && high_value == NULL_TREE)
+    switch_stack->has_default_p = true;
+
   if (processing_template_decl)
     {
       tree label;