[Spice-devel] [spice-gtk v2] widget: Do not mix function linkage

[Frediano Ziglio]

This prevents a possible crash on windows 32 bit.
The linkage of UnhookWindowsHookEx is WINAPI which is __stdcall while
callback for g_clear_pointer is C. This could cause stack pointer
corruption depending on compiler flags.
On __stdcall linkage function change the stack pointer while returning
from a function removing the parameters. On C linkage function leave
the stack pointer unchanged. So if the compiler call a __stdcall
function as a C function it expect the stack pointer to be unchanged
causing the pointer to be inconsistent by an offset.

Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
---
 src/spice-widget.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Changes from v1:
- extend commit message.

diff --git a/src/spice-widget.c b/src/spice-widget.c
index b5936bc..c528614 100644
--- a/src/spice-widget.c
+++ b/src/spice-widget.c
@@ -827,7 +827,11 @@ static void try_keyboard_ungrab(SpiceDisplay *display)
     SPICE_DEBUG("ungrab keyboard");
     gdk_keyboard_ungrab(GDK_CURRENT_TIME);
 #ifdef G_OS_WIN32
-    g_clear_pointer(&d->keyboard_hook, UnhookWindowsHookEx);
+    // do not use g_clear_pointer as Windows API have different linkage
+    if (d->keyboard_hook) {
+        UnhookWindowsHookEx(d->keyboard_hook);
+        d->keyboard_hook = NULL;
+    }
 #endif
     d->keyboard_grab_active = false;
     g_signal_emit(widget, signals[SPICE_DISPLAY_KEYBOARD_GRAB], 0, false);
-- 
2.7.4