[gnome-builder] libide/threading: helper to send signal upon cancellation

[Christian Hergert <chergert src gnome org>]

commit f21275b9a31cc096aa07a1c4ad59b347b6ddaaaf
Author: Christian Hergert <chergert redhat com>
Date:   Tue Jul 19 16:28:18 2022 -0700

    libide/threading: helper to send signal upon cancellation
    
    This allows us to easily chain a GCancellable::cancelled signal emission
    into a signal() to a subprocess. Use as such:
    
      ide_subprocess_send_signal_upon_cancel(subprocess, cancellable, SIGKILL);
    
    This uses weak refs to avoid any additional cycles on the objects and
    attempts to stop the connection based on where the reference is dropped
    (via GObject data list or GCancellable signal connection).

 src/libide/threading/ide-subprocess.c | 92 +++++++++++++++++++++++++++++++++++
 src/libide/threading/ide-subprocess.h |  6 ++-
 2 files changed, 97 insertions(+), 1 deletion(-)
---
diff --git a/src/libide/threading/ide-subprocess.c b/src/libide/threading/ide-subprocess.c
index 37e5a80d9..04eff0a0a 100644
--- a/src/libide/threading/ide-subprocess.c
+++ b/src/libide/threading/ide-subprocess.c
@@ -424,3 +424,95 @@ ide_subprocess_check_exit_status (IdeSubprocess  *self,
 
   return g_spawn_check_wait_status (exit_status, error);
 }
+
+typedef struct
+{
+  GWeakRef subprocess_wr;
+  GWeakRef cancellable_wr;
+  gpointer handler_id;
+  int signum;
+} CancelSignalData;
+
+static void
+signal_upon_cancel_activate (GCancellable *cancellable,
+                             gpointer      user_data)
+{
+  CancelSignalData *data = user_data;
+  g_autoptr(IdeSubprocess) subprocess = NULL;
+
+  g_assert (G_IS_CANCELLABLE (cancellable));
+  g_assert (data != NULL);
+
+  if ((subprocess = g_weak_ref_get (&data->subprocess_wr)))
+    ide_subprocess_send_signal (subprocess, data->signum);
+}
+
+static void
+cancel_signal_data_finalize (CancelSignalData *data)
+{
+  g_weak_ref_clear (&data->cancellable_wr);
+  g_weak_ref_clear (&data->subprocess_wr);
+}
+
+static void
+cancel_signal_data_invalidate_by_subprocess (CancelSignalData *data)
+{
+  g_autoptr(GCancellable) cancellable = NULL;
+  gulong handler_id;
+
+  g_assert (data != NULL);
+
+  g_weak_ref_set (&data->subprocess_wr, NULL);
+
+  handler_id = GPOINTER_TO_SIZE (g_atomic_pointer_exchange (&data->handler_id, NULL));
+  if (handler_id != 0 && (cancellable = g_weak_ref_get (&data->cancellable_wr)))
+    g_cancellable_disconnect (cancellable, handler_id);
+
+  g_atomic_rc_box_release_full (data, (GDestroyNotify)cancel_signal_data_finalize);
+}
+
+static void
+cancel_signal_data_invalidate_by_cancellable (CancelSignalData *data)
+{
+  g_autoptr(IdeSubprocess) subprocess = NULL;
+
+  g_assert (data != NULL);
+
+  g_weak_ref_set (&data->cancellable_wr, NULL);
+
+  if ((subprocess = g_weak_ref_get (&data->subprocess_wr)))
+    g_object_set_data (G_OBJECT (subprocess), "SIGNAL_UPON_CANCEL", NULL);
+
+  g_atomic_rc_box_release_full (data, (GDestroyNotify)cancel_signal_data_finalize);
+}
+
+void
+ide_subprocess_send_signal_upon_cancel (IdeSubprocess *self,
+                                        GCancellable  *cancellable,
+                                        int            signal_num)
+{
+  CancelSignalData *data;
+
+  g_return_if_fail (IDE_IS_SUBPROCESS (self));
+  g_return_if_fail (!cancellable || G_IS_CANCELLABLE (cancellable));
+
+  if (cancellable == NULL)
+    return;
+
+  data = g_atomic_rc_box_new0 (CancelSignalData);
+  g_weak_ref_init (&data->subprocess_wr, self);
+  g_weak_ref_init (&data->cancellable_wr, cancellable);
+  data->signum = signal_num;
+
+  g_object_set_data_full (G_OBJECT (self),
+                          "SIGNAL_UPON_CANCEL",
+                          g_atomic_rc_box_acquire (data),
+                          (GDestroyNotify)cancel_signal_data_invalidate_by_subprocess);
+
+  data->handler_id = GSIZE_TO_POINTER (g_cancellable_connect (cancellable,
+                                                              G_CALLBACK (signal_upon_cancel_activate),
+                                                              g_atomic_rc_box_acquire (data),
+                                                              
(GDestroyNotify)cancel_signal_data_invalidate_by_cancellable));
+
+  g_atomic_rc_box_release_full (data, (GDestroyNotify)cancel_signal_data_finalize);
+}
diff --git a/src/libide/threading/ide-subprocess.h b/src/libide/threading/ide-subprocess.h
index 9c20ea768..146a450dc 100644
--- a/src/libide/threading/ide-subprocess.h
+++ b/src/libide/threading/ide-subprocess.h
@@ -146,10 +146,14 @@ IDE_AVAILABLE_IN_ALL
 gint           ide_subprocess_get_status              (IdeSubprocess        *self);
 IDE_AVAILABLE_IN_ALL
 void           ide_subprocess_send_signal             (IdeSubprocess        *self,
-                                                       gint                  signal_num);
+                                                       int                   signal_num);
 IDE_AVAILABLE_IN_ALL
 void           ide_subprocess_force_exit              (IdeSubprocess        *self);
 IDE_AVAILABLE_IN_ALL
+void           ide_subprocess_send_signal_upon_cancel (IdeSubprocess        *self,
+                                                       GCancellable         *cancellable,
+                                                       int                   signal_num);
+IDE_AVAILABLE_IN_ALL
 gboolean       ide_subprocess_communicate             (IdeSubprocess        *self,
                                                        GBytes               *stdin_buf,
                                                        GCancellable         *cancellable,