Re: [PULL 14/14] ui: add precondition for dpy_get_ui_info()

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Sep 12, 2023 at 02:46:48PM +0400, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> Ensure that it only get called when dpy_ui_info_supported(). The
> function should always return a result. There should be a non-null
> console or active_console.

Empirically that does not appear to be the case. After this patch,
a no-args QEMU launch immediately aborts:

$ ./build/qemu-system-x86_64 
qemu-system-x86_64: ../ui/console.c:818: dpy_get_ui_info: Assertion `dpy_ui_info_supported(con)' failed.
Aborted (core dumped)

This ought to be running the GTK UI for me. Manually ask for
SDL instead and it doesn't crash.

> 
> Modify the argument to be const as well.
> 
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> Reviewed-by: Albert Esteve <aesteve@redhat.com>
> ---
>  include/ui/console.h | 2 +-
>  ui/console.c         | 4 +++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/include/ui/console.h b/include/ui/console.h
> index 79e4702912..28882f15a5 100644
> --- a/include/ui/console.h
> +++ b/include/ui/console.h
> @@ -329,7 +329,7 @@ void update_displaychangelistener(DisplayChangeListener *dcl,
>                                    uint64_t interval);
>  void unregister_displaychangelistener(DisplayChangeListener *dcl);
>  
> -bool dpy_ui_info_supported(QemuConsole *con);
> +bool dpy_ui_info_supported(const QemuConsole *con);
>  const QemuUIInfo *dpy_get_ui_info(const QemuConsole *con);
>  int dpy_set_ui_info(QemuConsole *con, QemuUIInfo *info, bool delay);
>  
> diff --git a/ui/console.c b/ui/console.c
> index aa1e09462c..4a4f19ed33 100644
> --- a/ui/console.c
> +++ b/ui/console.c
> @@ -801,7 +801,7 @@ static void dpy_set_ui_info_timer(void *opaque)
>      con->hw_ops->ui_info(con->hw, head, &con->ui_info);
>  }
>  
> -bool dpy_ui_info_supported(QemuConsole *con)
> +bool dpy_ui_info_supported(const QemuConsole *con)
>  {
>      if (con == NULL) {
>          con = active_console;
> @@ -815,6 +815,8 @@ bool dpy_ui_info_supported(QemuConsole *con)
>  
>  const QemuUIInfo *dpy_get_ui_info(const QemuConsole *con)
>  {
> +    assert(dpy_ui_info_supported(con));
> +
>      if (con == NULL) {
>          con = active_console;
>      }
> -- 
> 2.41.0
> 
> 

With regards,
Daniel
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