[gcc/devel/c++-coroutines] coroutines: Ensure distinct DTOR trees [PR95137].

[Iain D Sandoe]

https://gcc.gnu.org/g:006f28aefeb3be575239beddc7febe56dff463a2

commit 006f28aefeb3be575239beddc7febe56dff463a2
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Tue Jun 9 19:17:14 2020 +0100

    coroutines: Ensure distinct DTOR trees [PR95137].
    
    Part of the PR notes that there are UBSAN fails for the coroutines
    test suite.  These are primarily related to the use of the same DTOR
    tree in the two edges from the await block.  Fixed by building a new
    tree for each.
    
    gcc/cp/ChangeLog:
    
            PR c++/95137
            * coroutines.cc (expand_one_await_expression): Build separate
            DTOR trees for the awaitable object on the destroy and resume
            paths.

Diff:
---
 gcc/cp/coroutines.cc | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
index e86b3d42a7f..3c8c70f5317 100644
--- a/gcc/cp/coroutines.cc
+++ b/gcc/cp/coroutines.cc
@@ -1488,19 +1488,13 @@ expand_one_await_expression (tree *stmt, tree *await_expr, void *d)
   tree resume_label = create_named_label_with_ctx (loc, buf, actor);
   tree empty_list = build_empty_stmt (loc);
 
-  tree dtor = NULL_TREE;
   tree await_type = TREE_TYPE (var);
-  if (needs_dtor)
-    dtor = build_special_member_call (var, complete_dtor_identifier, NULL,
-				      await_type, LOOKUP_NORMAL,
-				      tf_warning_or_error);
-
   tree stmt_list = NULL;
   tree t_expr = STRIP_NOPS (expr);
   tree r;
   tree *await_init = NULL;
   if (t_expr == var)
-    dtor = NULL_TREE;
+    needs_dtor = false;
   else
     {
       /* Initialize the var from the provided 'o' expression.  */
@@ -1615,7 +1609,12 @@ expand_one_await_expression (tree *stmt, tree *await_expr, void *d)
   destroy_label = build_stmt (loc, LABEL_EXPR, destroy_label);
   append_to_statement_list (destroy_label, &body_list);
   if (needs_dtor)
-    append_to_statement_list (dtor, &body_list);
+    {
+      tree dtor = build_special_member_call (var, complete_dtor_identifier,
+					     NULL, await_type, LOOKUP_NORMAL,
+					     tf_warning_or_error);
+      append_to_statement_list (dtor, &body_list);
+    }
   r = build1_loc (loc, GOTO_EXPR, void_type_node, data->cleanup);
   append_to_statement_list (r, &body_list);
 
@@ -1650,7 +1649,12 @@ expand_one_await_expression (tree *stmt, tree *await_expr, void *d)
   /* Get a pointer to the revised statment.  */
   tree *revised = tsi_stmt_ptr (tsi_last (stmt_list));
   if (needs_dtor)
-    append_to_statement_list (dtor, &stmt_list);
+    {
+      tree dtor = build_special_member_call (var, complete_dtor_identifier,
+					     NULL, await_type, LOOKUP_NORMAL,
+					     tf_warning_or_error);
+      append_to_statement_list (dtor, &stmt_list);
+    }
   data->index += 2;
 
   /* Replace the original statement with the expansion.  */