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

[Jonathon Jongsma]

Acked-by: Jonathon Jongsma <jjongsma at redhat.com>



On Fri, 2016-06-10 at 10:56 +0100, Frediano Ziglio wrote:
> 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);