[Spice-devel] [PATCH spice-server v2] event-loop: Avoid possible compiler warning

[Frediano Ziglio]

With GCC 8.0.1 (Fedora 28), cast to different function pointer
can lead to warnings, like:

  event-loop.c: In function ‘watch_update_mask’:
  event-loop.c:146:42: error: cast between incompatible function types from ‘gboolean (*)(GIOChannel *, GIOCondition,  void *)’ {aka ‘int (*)(struct _GIOChannel *, enum <anonymous>,  void *)’} to ‘gboolean (*)(void *)’ {aka ‘int (*)(void *)’} [-Werror=cast-function-type]
       g_source_set_callback(watch->source, (GSourceFunc)watch_func, watch, NULL);
                                          ^
  cc1: all warnings being treated as errors

As g_source_set_callback expect a function pointer which type
changes based on the type of source (so is expected) silent
the possible warning.

Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
---
 server/event-loop.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/server/event-loop.c b/server/event-loop.c
index 582782e1..d3b7de1b 100644
--- a/server/event-loop.c
+++ b/server/event-loop.c
@@ -143,7 +143,12 @@ static void watch_update_mask(const SpiceCoreInterfaceInternal *iface,
         return;
 
     watch->source = g_io_create_watch(watch->channel, spice_event_to_giocondition(event_mask));
-    g_source_set_callback(watch->source, (GSourceFunc)watch_func, watch, NULL);
+    /* g_source_set_callback() documentation says:
+     * "The exact type of func depends on the type of source; ie. you should
+     *  not count on func being called with data as its first parameter."
+     * In this case is a GIOFunc. First cast (GIOFunc) make sure is the right type,
+     * other casts make possible warning silent */
+    g_source_set_callback(watch->source, (GSourceFunc)(void*)(GIOFunc)watch_func, watch, NULL);
     g_source_attach(watch->source, watch->context);
 }
 
-- 
2.17.0