在 2020/2/3 上午9:03, JunMa 写道:
在 2020/1/28 上午12:01, Nathan Sidwell 写道:
On 1/21/20 6:21 AM, JunMa wrote:
Hi
When test gcc with cppcoro, I find case like:

   int& awaitable::await_resume()
   auto x1 = co_await awaitable;
   decltype(auto) x2 = co_await awaitable;

Based on standard, typeof(x1) should be int, typeof(x2) is int&.
However, we get both x1 and x2 as int, this because we donot
consider indirect_ref which wrap await_resume call expression
(convert_from_reference), and it is invoked into type deduction
of auto and decltype(auto).

This patch wrap co_await expression with indirect_ref which should be
same with await_resume expression, and it sink await_resume expression
to real call_expr when replace co_await expression. it fix type deduction
of auto and decltype(auto) in coroutine.

Bootstrap and test on X86_64, is it OK?

+  /* Wrap co_await_expr.  */
+  if (TREE_CODE (awrs_call) == INDIRECT_REF)
+    await_expr = build1_loc (loc, INDIRECT_REF, TREE_TYPE (awrs_call),
+                 await_expr);

I think all you want here is:
  await_expr = convert_from_reference (await_expr);

Thanks, I'll update it.

Regards
JunMa
Hi nathan,
Here is the update.

Regards
JunMa

gcc/cp
2020-02-03  Jun Ma <ju...@linux.alibaba.com>

         * coroutines.cc (build_co_await): Call convert_from_reference
         to wrap co_await_expr with indirect_ref which avoid
         reference/non-reference type confusion.

         (co_await_expander):  Sink to call_expr if await_resume
         is wrapped by indirect_ref.

gcc/testsuite
2020-02-03  Jun Ma <ju...@linux.alibaba.com>

         * g++.dg/coroutines/co-await-14-return-ref-to-auto.C: New test.


Regards
JunMa

gcc/cp
2020-01-21  Jun Ma <ju...@linux.alibaba.com>

         * coroutines.cc (build_co_await): Wrap co_await with
         indirect_ref when needed.
         (co_await_expander):  Sink to call_expr if await_resume
         is wrapped by indirect_ref.

gcc/testsuite
2020-01-21  Jun Ma <ju...@linux.alibaba.com>

         * g++.dg/coroutines/co-await-14-return-ref-to-auto.C: Add label.



---
 gcc/cp/coroutines.cc                          | 12 +++--
 .../torture/co-await-14-return-ref-to-auto.C  | 45 +++++++++++++++++++
 2 files changed, 54 insertions(+), 3 deletions(-)
 create mode 100644 
gcc/testsuite/g++.dg/coroutines/torture/co-await-14-return-ref-to-auto.C

diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
index 62d92d9fc98..e7a150d257f 100644
--- a/gcc/cp/coroutines.cc
+++ b/gcc/cp/coroutines.cc
@@ -749,9 +749,12 @@ build_co_await (location_t loc, tree a, suspend_point_kind 
suspend_kind)
   TREE_VEC_ELT (awaiter_calls, 1) = awsp_call; /* await_suspend().  */
   TREE_VEC_ELT (awaiter_calls, 2) = awrs_call; /* await_resume().  */
 
-  return build5_loc (loc, CO_AWAIT_EXPR, TREE_TYPE (awrs_call), a,
-                    e_proxy, o, awaiter_calls,
-                    build_int_cst (integer_type_node, (int) suspend_kind));
+  tree await_expr = build5_loc (loc, CO_AWAIT_EXPR,
+                               TREE_TYPE (TREE_TYPE (awrs_func)),
+                               a, e_proxy, o, awaiter_calls,
+                               build_int_cst (integer_type_node,
+                                              (int) suspend_kind));
+  return convert_from_reference (await_expr);
 }
 
 tree
@@ -1512,6 +1515,9 @@ co_await_expander (tree *stmt, int * /*do_subtree*/, void 
*d)
   /* This will produce the value (if one is provided) from the co_await
      expression.  */
   tree resume_call = TREE_VEC_ELT (awaiter_calls, 2); /* await_resume().  */
+  if (TREE_CODE (resume_call) == INDIRECT_REF)
+    /* Sink to await_resume call_expr.  */
+    resume_call = TREE_OPERAND (resume_call, 0);
   switch (stmt_code)
     {
     default: /* not likely to work .. but... */
diff --git 
a/gcc/testsuite/g++.dg/coroutines/torture/co-await-14-return-ref-to-auto.C 
b/gcc/testsuite/g++.dg/coroutines/torture/co-await-14-return-ref-to-auto.C
new file mode 100644
index 00000000000..0a7c035ef2a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/coroutines/torture/co-await-14-return-ref-to-auto.C
@@ -0,0 +1,45 @@
+//  { dg-do run }
+
+/* The simplest valued co_await we can do.  */
+
+#include "../coro.h"
+
+// boiler-plate for tests of codegen
+#include "../coro1-ret-int-yield-int.h"
+
+
+coro1
+f ()
+{
+  int t1 = 5;
+  int t2 = 5;
+  auto gX = co_await coro1::suspend_always_intrefprt{t1};
+  if (gX != t1)
+         abort();
+  decltype(auto) gX1 = co_await coro1::suspend_always_intrefprt{t2};
+  if (&gX1 != &t2)
+         abort();
+  co_return t1 + 10;
+}
+
+int main ()
+{
+  PRINT ("main: create coro1");
+  struct coro1 f_coro = f ();
+  if (f_coro.handle.done())
+    {
+      PRINT ("main: we should not be 'done' [1]");
+      abort ();
+    }
+  PRINT ("main: resuming [1] initial suspend");
+  while (!f_coro.handle.done())
+    f_coro.handle.resume();
+  /* we should now have returned with the co_return (15) */
+  if (!f_coro.handle.done())
+    {
+      PRINT ("main: we should be 'done' ");
+      abort ();
+    }
+  puts ("main: done");
+  return 0;
+}
-- 
2.19.1.3.ge56e4f7

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