evas/callbacks: Prevent post_event_callback_call recursion.

If this function is called recursively, it will free the list of post
callbacks before the list stops being used, which will cause a segfault.

The only place where this seems to happen is on
https://phab.enlightenment.org/T124, probably due to the extensive mouse
events which are launched in an unexpected way.

This bug started happening after commit
164cc07237395f8fe6efa465e4f0c0c4863f78ed, where the
_elm_scroll_page_x_get() started being called by a post_event callback,
and forcing an edje recalc. This recalc triggered another post_event
callback, thus causing the mentioned segfault.

If there's a better way to prevent this from happening, please change
the mentioned code.

1 files changed, 5 insertions, 1 deletions

diff --git a/src/lib/evas/canvas/evas_callbacks.c b/src/lib/evas/canvas/evas_callbacks.c
index 4d1c16d511..b85cc39b32 100644
--- a/src/lib/evas/canvas/evas_callbacks.c
+++ b/src/lib/evas/canvas/evas_callbacks.c
@@ -152,9 +152,12 @@ _evas_post_event_callback_call(Evas *eo_e, Evas_Public_Data *e)
 {
    Evas_Post_Callback *pc;
    int skip = 0;
+   static int first_run = 1; // FIXME: This is a workaround to prevent this
+                             // function from being called recursively.
 
-   if (e->delete_me) return;
+   if (e->delete_me || (!first_run)) return;
    _evas_walk(e);
+   first_run = 0;
    EINA_LIST_FREE(e->post_events, pc)
      {
         if ((!skip) && (!e->delete_me) && (!pc->delete_me))
@@ -163,6 +166,7 @@ _evas_post_event_callback_call(Evas *eo_e, Evas_Public_Data *e)
           }
         EVAS_MEMPOOL_FREE(_mp_pc, pc);
      }
+   first_run = 1;
    _evas_unwalk(e);
 }