[Xcb] [PATCH 1/2] xcb_disconnect(): Fix leak with error connections

[Josh Triplett]

On Tue, Dec 31, 2013 at 03:57:16PM +0100, Uli Schlachter wrote:
> There are two kind of error connections in XCB. First, if something goes wrong
> while the connection is being set up, _xcb_conn_ret_error() is used to return a
> static connection in an error state. If something goes wrong later,
> _xcb_conn_shutdown() is used to set c->has_error.
> 
> This is important, because the static object that _xcb_conn_ret_error() returns
> must not be freed, while the dynamically allocated objects that go through
> _xcb_conn_shutdown() must obviously be properly deallocated.
> 
> This used to work correctly, but in 769acff0da8, xcb_disconnect() was made to
> ignore all connections in an error state completely. Fix this by only ignoring
> the few static error connections that we have.
> 
> This was tested with the following hack:
> 
>     xcb_connection_t *c = xcb_connect(NULL, NULL);
>     close(xcb_get_file_descriptor(c));
>     xcb_discard_reply(c, xcb_get_input_focus(c).sequence);
>     xcb_flush(c);
>     xcb_disconnect(c);
> 
> Valgrind confirms that xcb has a memory leak before this patch that this patch
> indeed fixes.
> 
> Signed-off-by: Uli Schlachter <psychon at znc.in>
> ---
>  src/xcb_conn.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/src/xcb_conn.c b/src/xcb_conn.c
> index 46390e1..9da11b0 100644
> --- a/src/xcb_conn.c
> +++ b/src/xcb_conn.c
> @@ -64,6 +64,7 @@ typedef struct {
>      uint16_t length;
>  } xcb_setup_generic_t;
>  
> +/* Keep this list in sync with xcb_disconnect()! */
>  static const int xcb_con_error = XCB_CONN_ERROR;
>  static const int xcb_con_closed_mem_er = XCB_CONN_CLOSED_MEM_INSUFFICIENT;
>  static const int xcb_con_closed_parse_er = XCB_CONN_CLOSED_PARSE_ERR;

Rather than a list that has to be kept in sync in two non-adjacent
places, how about writing a static inline is_static_error_conn function
and keeping it right next to these?

- Josh Triplett