bug#21651: 25.0.50; [PATCH] Memory leak: auto_fontset_alist has keys that are modified externally by mistake

[Dima Kogan]

This issue was discussed on the mailing list with the thread starting
here:

https://lists.gnu.org/archive/html/emacs-devel/2015-10/msg00550.html

A patch was proposed here:

https://lists.gnu.org/archive/html/emacs-devel/2015-10/msg00292.html

and is copied here as an attachment.

From: Dima Kogan <dima@secretsauce.net>
Date: Mon, 5 Oct 2015 11:21:12 -0700
Subject: (copy_font_spec) now makes a deeper copy of its input

---
 src/font.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/font.c b/src/font.c
index a52a653..0b2999e 100644
--- a/src/font.c
+++ b/src/font.c
@@ -3981,7 +3981,12 @@ copy_font_spec (Lisp_Object font)
   pcdr = spec->props + FONT_EXTRA_INDEX;
   for (tail = AREF (font, FONT_EXTRA_INDEX); CONSP (tail); tail = XCDR (tail))
     if (!EQ (XCAR (XCAR (tail)), QCfont_entity))
-      *pcdr = Fcons (XCAR (tail), Qnil), pcdr = xcdr_addr (*pcdr);
+      {
+        *pcdr = Fcons (Fcons( XCAR (XCAR (tail)),
+                              XCDR (XCAR (tail))),
+                       Qnil);
+        pcdr = xcdr_addr (*pcdr);
+      }
 
   XSETFONT (new_spec, spec);
   return new_spec;