Re: [PATCH v3 08/34] Always run async signal handlers in the main UI

[Simon Marchi <simon dot marchi at ericsson dot com>]

On 16-05-06 08:34 AM, Pedro Alves wrote:
> Async signal handlers have no connection to whichever was the current
> UI, and thus always run on the main one.
> 
> gdb/ChangeLog:
> yyyy-mm-dd  Pedro Alves  <palves@redhat.com>
> 
> 	* event-loop.c: Include top.h.
> 	(invoke_async_signal_handlers): Switch to the main UI.
> 	* event-top.c (main_ui_): Update comment.
> 	(main_ui): New global.
> 	* top.h (main_ui): Declare.
> ---
>  gdb/event-loop.c | 4 ++++
>  gdb/event-top.c  | 5 ++---
>  gdb/top.h        | 5 +++++
>  3 files changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/gdb/event-loop.c b/gdb/event-loop.c
> index 60ef2a5..fe28305 100644
> --- a/gdb/event-loop.c
> +++ b/gdb/event-loop.c
> @@ -35,6 +35,7 @@
>  #include "gdb_sys_time.h"
>  #include "gdb_select.h"
>  #include "observer.h"
> +#include "top.h"
>  
>  /* Tell create_file_handler what events we are interested in.
>     This is used by the select version of the event loop.  */
> @@ -967,6 +968,9 @@ invoke_async_signal_handlers (void)
>  	break;
>        any_ready = 1;
>        async_handler_ptr->ready = 0;
> +      /* Async signal handlers have no connection to whichever was the
> +	 current UI, and thus always run on the main one.  */
> +      current_ui = main_ui;
>        (*async_handler_ptr->proc) (async_handler_ptr->client_data);
>      }
>  
> diff --git a/gdb/event-top.c b/gdb/event-top.c
> index c6e3b7e..63f6896 100644
> --- a/gdb/event-top.c
> +++ b/gdb/event-top.c
> @@ -437,11 +437,10 @@ top_level_prompt (void)
>    return xstrdup (prompt);
>  }
>  
> -/* The main UI.  This is the UI that is bound to stdin/stdout/stderr.
> -   It always exists and is created automatically when GDB starts
> -   up.  */
> +/* The main UI.  */
>  static struct ui main_ui_;
>  
> +struct ui *main_ui = &main_ui_;

I'd suggest making the pointer const, to show (and make sure) that the main ui
never changes throughout the lifetime of the gdb instance:

  +struct ui * const main_ui = &main_ui_;

>  struct ui *current_ui = &main_ui_;
>  struct ui *ui_list = &main_ui_;

ui_list could be const for the same reason, while we're at it.