From a9eec9625ea7165292958be04899b057804192fb Mon Sep 17 00:00:00 2001
From: Iain Sandoe <iain@sandoe.co.uk>
Date: Wed, 10 Jun 2020 00:15:28 +0100
Subject: [PATCH] coroutines: Make call argument handling more robust [PR95440]

build_new_method_call is supposed to be able to handle a null
arguments list pointer (when the method has no parms).  There
were a couple of places where uses of the argument list pointer
were not defended against NULL.

gcc/cp/ChangeLog:

	PR c++/95440
	* call.c (add_candidates): Use vec_safe_length() for
	testing the arguments list.
	(build_new_method_call_1): Use vec_safe_is_empty() when
	checking for an empty args list.

gcc/testsuite/ChangeLog:

	PR c++/95440
	* g++.dg/coroutines/pr95440.C: New test.
---
 gcc/cp/call.c                             |  4 +--
 gcc/testsuite/g++.dg/coroutines/pr95440.C | 39 +++++++++++++++++++++++
 2 files changed, 41 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/coroutines/pr95440.C

diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 3c97b9846e2..b99959f76f9 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -5862,7 +5862,7 @@ add_candidates (tree fns, tree first_arg, const vec<tree, va_gc> *args,
 	}
 
       /* Don't bother reversing an operator with two identical parameters.  */
-      else if (args->length () == 2 && (flags & LOOKUP_REVERSED))
+      else if (vec_safe_length (args) == 2 && (flags & LOOKUP_REVERSED))
 	{
 	  tree parmlist = TYPE_ARG_TYPES (TREE_TYPE (fn));
 	  if (same_type_p (TREE_VALUE (parmlist),
@@ -10263,7 +10263,7 @@ build_new_method_call_1 (tree instance, tree fns, vec<tree, va_gc> **args,
 	  && !(flags & LOOKUP_ONLYCONVERTING)
 	  && cxx_dialect >= cxx20
 	  && CP_AGGREGATE_TYPE_P (basetype)
-	  && !user_args->is_empty ())
+	  && !vec_safe_is_empty (user_args))
 	{
 	  /* Create a CONSTRUCTOR from ARGS, e.g. {1, 2} from <1, 2>.  */
 	  tree list = build_tree_list_vec (user_args);
diff --git a/gcc/testsuite/g++.dg/coroutines/pr95440.C b/gcc/testsuite/g++.dg/coroutines/pr95440.C
new file mode 100644
index 00000000000..8542880d1ab
--- /dev/null
+++ b/gcc/testsuite/g++.dg/coroutines/pr95440.C
@@ -0,0 +1,39 @@
+#if __has_include(<coroutine>)
+#include <coroutine>
+#else
+#include <experimental/coroutine>
+namespace std { using namespace experimental; }
+#endif
+#if 0
+struct suspend_n {
+  const int x;
+  constexpr suspend_n (int x) : x (x) {}
+  constexpr static bool await_ready() { return false; }
+  constexpr static void await_suspend(std::coroutine_handle<>) {}
+  constexpr static void await_resume() {}
+};
+#endif
+struct task
+{
+  struct promise_type
+  {
+    auto get_return_object() const { return task{}; }
+#if 0
+//    static constexpr suspend_n initial_suspend()  { return {2}; }
+#endif
+    static constexpr std::suspend_always initial_suspend()  { return {}; }
+    static constexpr std::suspend_never final_suspend() { return {}; }
+    static constexpr void return_void() {}
+    static constexpr void unhandled_exception() {}
+  };
+};
+
+task
+test_task ()
+{
+  co_await std::suspend_always{};
+}
+
+auto t = test_task();
+
+int main() {}
-- 
2.30.2