Avoid crashes when X fonts are erroneously freed on reused X

'Display *' connection data (Bug#16069).  Note that X font
resources still may be leaked, but currently there is no way
to completely avoid it.
* xterm.h (struct x_display_info): New member x_id.  Add comments.
* xterm.c (x_display_id): New variable.
(x_term_init): Assign identifier to each opened X connection.
* xfont.c (struct xfont): New member x_display_id.
(xfont_open): Initialize it with frame's display id.
(xfont_close): Check whether font's display id matches the one
recorded for the given display.  Adjust comment.
* xftfont.c (struct xftfont_info):
(xftfont_open, xftfont_close): Exactly as above with xfont stuff.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/xterm.c b/src/xterm.c
index e1873127276..f06225002a7 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -9679,6 +9679,10 @@ my_log_handler (const gchar *log_domain, GLogLevelFlags log_level,
 }
 #endif
 
+/* Current X display connection identifier.  Incremented for each next
+   connection established.  */
+static unsigned x_display_id;
+
 /* Open a connection to X display DISPLAY_NAME, and return
    the structure that describes the open display.
    If we cannot contact the display, return null.  */
@@ -9896,6 +9900,7 @@ x_term_init (Lisp_Object display_name, char *xrm_option, char *resource_name)
   lim = min (PTRDIFF_MAX, SIZE_MAX) - sizeof "@";
   if (lim - SBYTES (Vinvocation_name) < SBYTES (Vsystem_name))
     memory_full (SIZE_MAX);
+  dpyinfo->x_id = ++x_display_id;
   dpyinfo->x_id_name = xmalloc (SBYTES (Vinvocation_name)
                                 + SBYTES (Vsystem_name) + 2);
   strcat (strcat (strcpy (dpyinfo->x_id_name, SSDATA (Vinvocation_name)), "@"),