Fix a few crashes and leaks when cloning C strings.

* alloc.c, lisp.h (dupstring): New function.
* gtkutil.c (xg_get_font):
* term.c (tty_default_color_capabilities):
* xsettings.c (store_monospaced_changed)
(store_font_name_changed, parse_settings)
(read_and_apply_settings, init_gsettings, init_gconf): Use it.
This avoids some unlikely crashes due to accessing freed storage,
and avoids some minor memory leaks in the more-typical case.

1 files changed, 14 insertions, 0 deletions

diff --git a/src/alloc.c b/src/alloc.c
index 7f0a74ca834..7c671e25cfc 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -850,6 +850,20 @@ xlispstrdup (Lisp_Object string)
   return memcpy (xmalloc (size), SSDATA (string), size);
 }
 
+/* Assign to *PTR a copy of STRING, freeing any storage *PTR formerly
+   pointed to.  If STRING is null, assign it without copying anything.
+   Allocate before freeing, to avoid a dangling pointer if allocation
+   fails.  */
+
+void
+dupstring (char **ptr, char const *string)
+{
+  char *old = *ptr;
+  *ptr = string ? xstrdup (string) : 0;
+  xfree (old);
+}
+
+
 /* Like putenv, but (1) use the equivalent of xmalloc and (2) the
    argument is a const pointer.  */