Re: [PATCH] coroutines: Build pointer initializers with nullptr_node [PR107768]

[Jason Merrill via Gcc-patches]

On 12/10/22 10:54, Iain Sandoe wrote:

From: Andrew Pinski <pins...@gmail.com>

This is Andrew Pinski's patch, I just did testing, adjusted the test case and
provided the Changelog.
tested on x86-64-Darwin21,
OK for trunk?
Iain

OK.

--- >8 ---

The PR reports that using integer_zero_node triggers a warning for
-Wzero-as-null-pointer-constant which comes from compiler-generated code so
makes no sense to the end user.

Co-Authored-By: Iain Sandoe <i...@sandoe.co.uk>

        PR c++/107768

gcc/cp/ChangeLog:

        * coroutines.cc (coro_rewrite_function_body): Initialize pointers
        from nullptr_node.  (morph_fn_to_coro): Likewise.

gcc/testsuite/ChangeLog:

        * g++.dg/coroutines/pr107768.C: New test.
---
  gcc/cp/coroutines.cc                       |  6 ++---
  gcc/testsuite/g++.dg/coroutines/pr107768.C | 26 ++++++++++++++++++++++
  2 files changed, 29 insertions(+), 3 deletions(-)
  create mode 100644 gcc/testsuite/g++.dg/coroutines/pr107768.C

diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
index 3f23317a315..88d6c30d8b1 100644
--- a/gcc/cp/coroutines.cc
+++ b/gcc/cp/coroutines.cc
@@ -4132,7 +4132,7 @@ coro_rewrite_function_body (location_t fn_start, tree 
fnbody, tree orig,
    /* We will need to be able to set the resume function pointer to nullptr
       to signal that the coroutine is 'done'.  */
    tree zero_resume
-    = build1 (CONVERT_EXPR, resume_fn_ptr_type, integer_zero_node);
+    = build1 (CONVERT_EXPR, resume_fn_ptr_type, nullptr_node);

/* The pointer to the destroy function. */

    tree var = coro_build_artificial_var (fn_start, coro_destroy_fn_id,
@@ -4519,7 +4519,7 @@ morph_fn_to_coro (tree orig, tree *resumer, tree 
*destroyer)
    tree ramp_body = push_stmt_list ();

tree zeroinit = build1_loc (fn_start, CONVERT_EXPR,

-                             coro_frame_ptr, integer_zero_node);
+                             coro_frame_ptr, nullptr_node);
    tree coro_fp = coro_build_artificial_var (fn_start, "_Coro_frameptr",
                                            coro_frame_ptr, orig, zeroinit);
    tree varlist = coro_fp;
@@ -4754,7 +4754,7 @@ morph_fn_to_coro (tree orig, tree *resumer, tree 
*destroyer)

gcc_checking_assert (same_type_p (fn_return_type, TREE_TYPE (grooaf)));

        tree if_stmt = begin_if_stmt ();
-      tree cond = build1 (CONVERT_EXPR, coro_frame_ptr, integer_zero_node);
+      tree cond = build1 (CONVERT_EXPR, coro_frame_ptr, nullptr_node);
        cond = build2 (EQ_EXPR, boolean_type_node, coro_fp, cond);
        finish_if_stmt_cond (cond, if_stmt);
        if (VOID_TYPE_P (fn_return_type))
diff --git a/gcc/testsuite/g++.dg/coroutines/pr107768.C 
b/gcc/testsuite/g++.dg/coroutines/pr107768.C
new file mode 100644
index 00000000000..22d7074f261
--- /dev/null
+++ b/gcc/testsuite/g++.dg/coroutines/pr107768.C
@@ -0,0 +1,26 @@
+//  { dg-additional-options "-Wzero-as-null-pointer-constant -fsyntax-only" }
+
+#include <coroutine>
+
+struct task
+{
+    struct promise_type
+    {
+        task get_return_object() { return {}; }
+        std::suspend_never initial_suspend() { return {}; }
+        std::suspend_never final_suspend() noexcept { return {}; }
+        void return_void() {}
+        void unhandled_exception() {}
+    };
+};
+
+task resuming_on_new_thread(void)
+{
+    struct awaitable
+    {
+        bool await_ready() { return false; }
+        void await_suspend(std::coroutine_handle<> h)         {         }
+        void await_resume() {}
+    };
+    co_await awaitable{};
+}