[glib: 1/2] gmain: Fix reference leak of GMainLoop in some situations

[Emmanuele Bassi <ebassi src gnome org>]

commit 4f5da8338127e25e5ebb54f5a4a95ffc2e40adcc
Author: Philip Withnall <pwithnall endlessos org>
Date:   Fri Mar 4 17:37:09 2022 +0000

    gmain: Fix reference leak of GMainLoop in some situations
    
    When calling `g_main_loop_run()` it’s possible for a reference to the
    `GMainLoop` to leak if this thread had to wait to acquire ownership of
    the `GMainContext`.
    
    Signed-off-by: Philip Withnall <pwithnall endlessos org>
    
    Fixes: #2598

 glib/gmain.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/glib/gmain.c b/glib/gmain.c
index 0e757a6f6..94aa1152a 100644
--- a/glib/gmain.c
+++ b/glib/gmain.c
@@ -4367,6 +4367,9 @@ g_main_loop_run (GMainLoop *loop)
   g_return_if_fail (loop != NULL);
   g_return_if_fail (g_atomic_int_get (&loop->ref_count) > 0);
 
+  /* Hold a reference in case the loop is unreffed from a callback function */
+  g_atomic_int_inc (&loop->ref_count);
+
   if (!g_main_context_acquire (loop->context))
     {
       gboolean got_ownership = FALSE;
@@ -4374,7 +4377,6 @@ g_main_loop_run (GMainLoop *loop)
       /* Another thread owns this context */
       LOCK_CONTEXT (loop->context);
 
-      g_atomic_int_inc (&loop->ref_count);
       g_atomic_int_set (&loop->is_running, TRUE);
 
       while (g_atomic_int_get (&loop->is_running) && !got_ownership)
@@ -4400,10 +4402,10 @@ g_main_loop_run (GMainLoop *loop)
     {
       g_warning ("g_main_loop_run(): called recursively from within a source's "
                 "check() or prepare() member, iteration not possible.");
+      g_main_loop_unref (loop);
       return;
     }
 
-  g_atomic_int_inc (&loop->ref_count);
   g_atomic_int_set (&loop->is_running, TRUE);
   while (g_atomic_int_get (&loop->is_running))
     g_main_context_iterate (loop->context, TRUE, TRUE, self);