[Emacs-diffs] /srv/bzr/emacs/trunk r110854: Tweak last vectorlike_header change.

[Dmitry Antipov]

------------------------------------------------------------
revno: 110854
committer: Dmitry Antipov <address@hidden>
branch nick: trunk
timestamp: Fri 2012-11-09 15:38:31 +0400
message:
  Tweak last vectorlike_header change.
  * alloc.c (struct Lisp_Vectorlike_Free): Special type to represent
  vectorlike object on the free list.  This is introduced to avoid
  some (but not all) pointer casting and aliasing problems, see
  http://lists.gnu.org/archive/html/emacs-devel/2012-11/msg00105.html.
  * .gdbinit (pvectype, pvecsize): New commands to examine vectorlike
  objects.
  (xvectype, xvecsize): Use them to examine Lisp_Object values.
modified:
  src/.gdbinit
  src/ChangeLog
  src/alloc.c

=== modified file 'src/.gdbinit'
--- a/src/.gdbinit      2012-11-08 14:10:28 +0000
+++ b/src/.gdbinit      2012-11-09 11:38:31 +0000
@@ -650,9 +650,8 @@
 a second line gives the more precise type.
 end
 
-define xvectype
-  xgetptr $
-  set $size = ((struct Lisp_Vector *) $ptr)->header.size
+define pvectype
+  set $size = ((struct Lisp_Vector *) $arg0)->header.size
   if ($size & PSEUDOVECTOR_FLAG)
     output (enum pvec_type) (($size & PVEC_TYPE_MASK) >> 
PSEUDOVECTOR_AREA_BITS)
   else
@@ -660,14 +659,22 @@
   end
   echo \n
 end
+document pvectype
+Print the subtype of vectorlike object.
+Takes one argument, a pointer to an object.
+end
+
+define xvectype
+  xgetptr $
+  pvectype $ptr
+end
 document xvectype
-Print the type or vector subtype of $.
-This command assumes that $ is a vector or pseudovector.
+Print the subtype of vectorlike object.
+This command assumes that $ is a Lisp_Object.
 end
 
-define xvecsize
-  xgetptr $
-  set $size = ((struct Lisp_Vector *) $ptr)->header.size
+define pvecsize
+  set $size = ((struct Lisp_Vector *) $arg0)->header.size
   if ($size & PSEUDOVECTOR_FLAG)
     output ($size & PSEUDOVECTOR_SIZE_MASK)
     echo \n
@@ -677,9 +684,18 @@
   end
   echo \n
 end
+document pvecsize
+Print the size of vectorlike object.
+Takes one argument, a pointer to an object.
+end
+
+define xvecsize
+  xgetptr $
+  pvecsize $ptr
+end
 document xvecsize
-Print the size or vector subtype of $.
-This command assumes that $ is a vector or pseudovector.
+Print the size of $
+This command assumes that $ is a Lisp_Object.
 end
 
 define xmisctype

=== modified file 'src/ChangeLog'
--- a/src/ChangeLog     2012-11-09 06:36:51 +0000
+++ b/src/ChangeLog     2012-11-09 11:38:31 +0000
@@ -1,3 +1,14 @@
+2012-11-09  Dmitry Antipov  <address@hidden>
+
+       Tweak last vectorlike_header change.
+       * alloc.c (struct Lisp_Vectorlike_Free): Special type to represent
+       vectorlike object on the free list.  This is introduced to avoid
+       some (but not all) pointer casting and aliasing problems, see
+       http://lists.gnu.org/archive/html/emacs-devel/2012-11/msg00105.html.
+       * .gdbinit (pvectype, pvecsize): New commands to examine vectorlike
+       objects.
+       (xvectype, xvecsize): Use them to examine Lisp_Object values.
+
 2012-11-09  Jan Djärv  <address@hidden>
 
        * nsfont.m (ns_descriptor_to_entity): Qcondesed and Qexpanded has

=== modified file 'src/alloc.c'
--- a/src/alloc.c       2012-11-08 19:12:23 +0000
+++ b/src/alloc.c       2012-11-09 11:38:31 +0000
@@ -2611,16 +2611,18 @@
 
 #define VINDEX(nbytes) (((nbytes) - VBLOCK_BYTES_MIN) / roundup_size)
 
-/* When V is on the free list, first word after header is used as a pointer
-   to next vector on the free list.  It might be done in a better way with:
-
-   (*(struct Lisp_Vector **)&(v->contents[0]))
-
-   but this breaks GCC's strict-aliasing rules (which looks more relaxed
-   for char and void pointers).  */
-
-#define NEXT_IN_FREE_LIST(v)                           \
-  (*(struct Lisp_Vector **)((char *) v + header_size))
+/* This special type is used to represent any block-allocated vectorlike
+   object on the free list.  */
+
+struct Lisp_Vectorlike_Free
+{
+  struct vectorlike_header header;
+  struct Lisp_Vector *next;
+};
+
+/* When V is on the free list, it's always treated as Lisp_Vectorlike_Free.  */
+
+#define NEXT_IN_FREE_LIST(v) ((struct Lisp_Vectorlike_Free *) v)->next
 
 /* Common shortcut to setup vector on a free list.  */