[gcc r10-9514] coroutines : Adjust constraints on when to build ctors [PR98118].

[Iain D Sandoe]

https://gcc.gnu.org/g:fad6d041ebf191eecdc98e162869c2f4a6eb245f

commit r10-9514-gfad6d041ebf191eecdc98e162869c2f4a6eb245f
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Wed Feb 17 15:13:57 2021 +0000

    coroutines : Adjust constraints on when to build ctors [PR98118].
    
    PR98118 shows that TYPE_NEEDS_CONSTRUCTING is necessary but not
    sufficient.  Use type_build_ctor_call() instead.
    
    gcc/cp/ChangeLog:
    
            PR c++/98118
            * coroutines.cc (build_co_await): Use type_build_ctor_call()
            to determine cases when a CTOR needs to be built.
            (flatten_await_stmt): Likewise.
            (morph_fn_to_coro): Likewise.
    
    gcc/testsuite/ChangeLog:
    
            PR c++/98118
            * g++.dg/coroutines/pr98118.C: New test.
    
    (cherry picked from commit 3d9577c254003f2d18185015b75ce6e3e4af9ca2)

Diff:
---
 gcc/cp/coroutines.cc                      | 14 +++++++-------
 gcc/testsuite/g++.dg/coroutines/pr98118.C | 29 +++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 7 deletions(-)

diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
index 44f4946d7a3..582ee9489c5 100644
--- a/gcc/cp/coroutines.cc
+++ b/gcc/cp/coroutines.cc
@@ -950,7 +950,7 @@ build_co_await (location_t loc, tree a, suspend_point_kind suspend_kind)
       e_proxy = o;
       o = NULL_TREE; /* The var is already present.  */
     }
-  else if (CLASS_TYPE_P (o_type) || TYPE_NEEDS_CONSTRUCTING (o_type))
+  else if (type_build_ctor_call (o_type))
     {
       e_proxy = get_awaitable_var (suspend_kind, o_type);
       releasing_vec arg (make_tree_vector_single (rvalue (o)));
@@ -2985,7 +2985,7 @@ flatten_await_stmt (var_nest_node *n, hash_set<tree> *promoted,
 	  gcc_checking_assert (!already_present);
 	  tree inner = TREE_OPERAND (init, 1);
 	  gcc_checking_assert (TREE_CODE (inner) != COND_EXPR);
-	  if (TYPE_NEEDS_CONSTRUCTING (var_type))
+	  if (type_build_ctor_call (var_type))
 	    {
 	      releasing_vec p_in (make_tree_vector_single (init));
 	      init = build_special_member_call (var, complete_ctor_identifier,
@@ -2997,9 +2997,9 @@ flatten_await_stmt (var_nest_node *n, hash_set<tree> *promoted,
 	  var_nest_node *ins
 	    = new var_nest_node (var, init, n->prev, n);
 	  /* We have to replace the target expr... */
-	  proxy_replace pr = {TREE_OPERAND (t, 0), var};
 	  *v.entry = var;
 	  /* ... and any uses of its var.  */
+	  proxy_replace pr = {TREE_OPERAND (t, 0), var};
 	  cp_walk_tree (&n->init, replace_proxy, &pr, NULL);
 	  /* Compiler-generated temporaries can also have uses in following
 	     arms of compound expressions, which will be listed in 'replace_in'
@@ -4709,7 +4709,7 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
 				   parm.frame_type, INIT_EXPR,
 				   DECL_SOURCE_LOCATION (arg), arg,
 				   DECL_ARG_TYPE (arg));
-	  else if (TYPE_NEEDS_CONSTRUCTING (parm.frame_type))
+	  else if (type_build_ctor_call (parm.frame_type))
 	    {
 	      vec<tree, va_gc> *p_in;
 	      if (CLASS_TYPE_P (parm.frame_type)
@@ -4767,7 +4767,7 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
 					   false, tf_warning_or_error);
 
   tree promise_dtor = NULL_TREE;
-  if (TYPE_NEEDS_CONSTRUCTING (promise_type))
+  if (type_build_ctor_call (promise_type))
     {
       /* Do a placement new constructor for the promise type (we never call
 	 the new operator, just the constructor on the object in place in the
@@ -4848,7 +4848,7 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
 	The expression promise.get_return_object() is used to initialize the
 	glvalue result or... (see below)
 	Construct the return result directly.  */
-      if (TYPE_NEEDS_CONSTRUCTING (gro_type))
+      if (type_build_ctor_call (gro_type))
 	{
 	  vec<tree, va_gc> *arg = make_tree_vector_single (get_ro);
 	  r = build_special_member_call (DECL_RESULT (orig),
@@ -4879,7 +4879,7 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
       DECL_CONTEXT (gro) = current_scope ();
       add_decl_expr (gro);
       gro_bind_vars = gro;
-      if (TYPE_NEEDS_CONSTRUCTING (gro_type))
+      if (type_build_ctor_call (gro_type))
 	{
 	  vec<tree, va_gc> *arg = make_tree_vector_single (get_ro);
 	  r = build_special_member_call (gro, complete_ctor_identifier,
diff --git a/gcc/testsuite/g++.dg/coroutines/pr98118.C b/gcc/testsuite/g++.dg/coroutines/pr98118.C
new file mode 100644
index 00000000000..d09ffff2142
--- /dev/null
+++ b/gcc/testsuite/g++.dg/coroutines/pr98118.C
@@ -0,0 +1,29 @@
+namespace std {
+inline namespace __n4861 {
+template <typename _Result, typename> struct coroutine_traits : _Result {};
+template <typename = void> struct coroutine_handle;
+template <> struct coroutine_handle<> {};
+template <typename> struct coroutine_handle : coroutine_handle<> {};
+struct suspend_never {
+  bool await_ready() noexcept;
+  void await_suspend(coroutine_handle<>) noexcept;
+  void await_resume() noexcept;
+};
+} // namespace __n4861
+} // namespace std
+
+struct fire_and_forget {
+  struct promise_type {
+    fire_and_forget get_return_object();
+    std::suspend_never initial_suspend();
+    std::suspend_never final_suspend() noexcept;
+    void return_void();
+    void unhandled_exception();
+  };
+};
+
+struct bug {
+  ~bug();
+};
+
+fire_and_forget f(bug) { co_return; }