[Emacs-diffs] /srv/bzr/emacs/trunk r109149: Remove some struct layout assumptions in bool vectors.

[Paul Eggert]

------------------------------------------------------------
revno: 109149
committer: Paul Eggert <address@hidden>
branch nick: trunk
timestamp: Wed 2012-07-18 10:26:43 -0700
message:
  Remove some struct layout assumptions in bool vectors.
  
  * alloc.c (bool_header_size): New constant.
  (header_size, word_size): Move earlier, as they're now used earlier.
  Use 'word_size' in a few more places, where it's appropriate.
  (Fmake_bool_vector, sweep_vectors): Don't assume that there is no
  padding before the data member of a bool vector.
  (sweep_vectors): Use PSEUDOVECTOR_TYPEP, in an eassert, rather
  than doing the check by hand with an abort ().
modified:
  src/ChangeLog
  src/alloc.c

=== modified file 'src/ChangeLog'
--- a/src/ChangeLog     2012-07-18 15:20:33 +0000
+++ b/src/ChangeLog     2012-07-18 17:26:43 +0000
@@ -1,3 +1,14 @@
+2012-07-18  Paul Eggert  <address@hidden>
+
+       Remove some struct layout assumptions in bool vectors.
+       * alloc.c (bool_header_size): New constant.
+       (header_size, word_size): Move earlier, as they're now used earlier.
+       Use 'word_size' in a few more places, where it's appropriate.
+       (Fmake_bool_vector, sweep_vectors): Don't assume that there is no
+       padding before the data member of a bool vector.
+       (sweep_vectors): Use PSEUDOVECTOR_TYPEP, in an eassert, rather
+       than doing the check by hand with an abort ().
+
 2012-07-18  Stefan Monnier  <address@hidden>
 
        * eval.c (Fdefvar): Don't check constants since we only set the var if

=== modified file 'src/alloc.c'
--- a/src/alloc.c       2012-07-18 09:46:07 +0000
+++ b/src/alloc.c       2012-07-18 17:26:43 +0000
@@ -281,6 +281,14 @@
 static void free_misc (Lisp_Object);
 extern Lisp_Object which_symbols (Lisp_Object, EMACS_INT) EXTERNALLY_VISIBLE;
 
+/* Handy constants for vectorlike objects.  */
+enum
+  {
+    header_size = offsetof (struct Lisp_Vector, contents),
+    bool_header_size = offsetof (struct Lisp_Bool_Vector, data),
+    word_size = sizeof (Lisp_Object)
+  };
+
 /* When scanning the C stack for live Lisp objects, Emacs keeps track
    of what memory allocated via lisp_malloc is intended for what
    purpose.  This enumeration specifies the type of memory.  */
@@ -2356,6 +2364,8 @@
   ptrdiff_t length_in_chars;
   EMACS_INT length_in_elts;
   int bits_per_value;
+  int extra_bool_elts = ((bool_header_size - header_size + word_size - 1)
+                        / word_size);
 
   CHECK_NATNUM (length);
 
@@ -2363,9 +2373,7 @@
 
   length_in_elts = (XFASTINT (length) + bits_per_value - 1) / bits_per_value;
 
-  /* We must allocate one more elements than LENGTH_IN_ELTS for the
-     slot `size' of the struct Lisp_Bool_Vector.  */
-  val = Fmake_vector (make_number (length_in_elts + 1), Qnil);
+  val = Fmake_vector (make_number (length_in_elts + extra_bool_elts), Qnil);
 
   /* No Lisp_Object to trace in there.  */
   XSETPVECTYPESIZE (XVECTOR (val), PVEC_BOOL_VECTOR, 0);
@@ -2874,12 +2882,10 @@
 
 #define VECTOR_BLOCK_SIZE 4096
 
-/* Handy constants for vectorlike objects.  */
+/* Align allocation request sizes to be a multiple of ROUNDUP_SIZE.  */
 enum
   {
-    header_size = offsetof (struct Lisp_Vector, contents),
-    word_size = sizeof (Lisp_Object),
-    roundup_size = COMMON_MULTIPLE (sizeof (Lisp_Object),
+    roundup_size = COMMON_MULTIPLE (word_size,
                                    USE_LSB_TAG ? 1 << GCTYPEBITS : 1)
   };
 
@@ -2905,7 +2911,7 @@
 /* Size of the largest vector allocated from block.  */
 
 #define VBLOCK_BYTES_MAX                                       \
-  vroundup ((VECTOR_BLOCK_BYTES / 2) - sizeof (Lisp_Object))
+  vroundup ((VECTOR_BLOCK_BYTES / 2) - word_size)
 
 /* We maintain one free list for each possible block-allocated
    vector size, and this is the number of free lists we have.  */
@@ -3154,25 +3160,21 @@
          total_vectors++;
          if (vector->header.size & PSEUDOVECTOR_FLAG)
            {
-             if (((vector->header.size & PVEC_TYPE_MASK)
-                  >> PSEUDOVECTOR_SIZE_BITS) == PVEC_BOOL_VECTOR)
-               {
-                 struct Lisp_Bool_Vector *b
-                   = (struct Lisp_Bool_Vector *) vector;
-                 total_vector_bytes += header_size + sizeof (b->size)
-                   + (b->size + BOOL_VECTOR_BITS_PER_CHAR - 1)
-                   / BOOL_VECTOR_BITS_PER_CHAR;
-               }
-             else
-               /* All other pseudovectors are small enough to be
-                  allocated from vector blocks.  This code should
-                  be redesigned if some pseudovector type grows
-                  beyond VBLOCK_BYTES_MAX.  */
-               abort ();
+             struct Lisp_Bool_Vector *b = (struct Lisp_Bool_Vector *) vector;
+
+             /* All non-bool pseudovectors are small enough to be allocated
+                from vector blocks.  This code should be redesigned if some
+                pseudovector type grows beyond VBLOCK_BYTES_MAX.  */
+             eassert (PSEUDOVECTOR_TYPEP (&vector->header, PVEC_BOOL_VECTOR));
+
+             total_vector_bytes
+               += (bool_header_size
+                   + ((b->size + BOOL_VECTOR_BITS_PER_CHAR - 1)
+                      / BOOL_VECTOR_BITS_PER_CHAR));
            }
          else
-           total_vector_bytes
-             += header_size + vector->header.size * word_size;
+           total_vector_bytes += (header_size
+                                  + vector->header.size * word_size);
          vprev = &vector->header.next.vector;
        }
       else
@@ -5261,8 +5263,7 @@
 {
   Lisp_Object new;
   struct Lisp_Vector *p;
-  size_t size = (offsetof (struct Lisp_Vector, contents)
-                + len * sizeof (Lisp_Object));
+  size_t size = header_size + len * word_size;
 
   p = (struct Lisp_Vector *) pure_alloc (size, Lisp_Vectorlike);
   XSETVECTOR (new, p);