Backport revisions 2011-04-24T05:30:24Z!eggert@cs.ucla.edu..2011-04-25T19:40:22Z!eggert@cs.ucla.edu (inclusive) from trunk (bug#8623)

	The next log entry shows the actual changes by Paul Eggert.

 Fix a problem with aliasing and vector headers.
 GCC 4.6.0 optimizes based on type-based alias analysis.  For
 example, if b is of type struct buffer * and v of type struct
 Lisp_Vector *, then gcc -O2 was incorrectly assuming that &b->size
 != &v->size, and therefore "v->size = 1; b->size = 2; return
 v->size;" must therefore return 1.  This assumption is incorrect
 for Emacs, since it type-puns struct Lisp_Vector * with many other
 types.  To fix this problem, this patch adds a new type struct
 vector_header that documents the constraints on layout of vectors
 and pseudovectors, and helps optimizing compilers not get fooled
 by Emacs's type punning.  It also adds the macros XSETTYPED_PVECTYPE
 XSETTYPED_PSEUDOVECTOR, TYPED_PSEUDOVECTORP, for similar reasons.
 src/lisp.h (XVECTOR_SIZE): New convenience macro.  All previous uses of
 XVECTOR (foo)->size replaced to use this macro, to avoid the hassle
 of writing XVECTOR (foo)->header.size.
 src/lisp.h: Say "vectorlike header" rather than "vector header.
 (struct vectorlike_header): Rename from struct vector_header.
 (XVECTORLIKE_HEADER_SIZE): Renamed from XVECTOR_HEADER_SIZE.
 All uses changed.
 (XVECTOR_HEADER_SIZE): New macro, for use in XSETPSEUDOVECTOR.
 (XSETTYPED_PVECTYPE): New macro, specifying the name of the size
 member.
 (XSETPVECTYPE): Rewrite in terms of new macro.
 (XSETPVECTYPESIZE): New macro, specifying both type and size.
 This is a bit clearer, and further avoids the possibility of
 undesirable aliasing.
 (XSETTYPED_PSEUDOVECTOR): New macro, specifying the size.
 (XSETPSEUDOVECTOR): Rewrite in terms of XSETTYPED_PSEUDOVECTOR
 and XVECTOR_HEADER_SIZE.
 (XSETSUBR): Rewrite in terms of XSETTYPED_PSEUDOVECTOR and XSIZE,
 since Lisp_Subr is a special case (no "next" field).
 (ASIZE): Rewrite in terms of XVECTOR_SIZE.
 (struct vector_header): New type.
 (TYPED_PSEUDOVECTORP): New macro, also specifying the C type of the
 object, to help avoid aliasing.
 (PSEUDOVECTORP): Rewrite in terms of TYPED_PSEUDOVECTORP.
 (SUBRP): Likewise, since Lisp_Subr is a special case.
 src/lisp.h (struct Lisp_Vector, struct Lisp_Char_Table):
 (struct Lisp_Sub_Char_Table, struct Lisp_Bool_Vector):
 (struct Lisp_Hash_Table): Combine first two members into a single
 struct vector_header member.  All uses of "size" and "next" members
 changed to be "header.size" and "header.next".
 src/buffer.h (struct buffer): Likewise.
 src/font.h (struct font_spec, struct font_entity, struct font): Likewise.
 src/frame.h (struct frame): Likewise.
 src/process.h (struct Lisp_Process): Likewise.
 src/termhooks.h (struct terminal): Likewise.
 src/window.c (struct save_window_data, struct saved_window): Likewise.
 src/window.h (struct window): Likewise.
 src/alloc.c (allocate_buffer, Fmake_bool_vector, allocate_pseudovector):
 Use XSETPVECTYPESIZE, not XSETPVECTYPE, to avoid aliasing problems.
 src/buffer.c (init_buffer_once): Likewise.
 src/lread.c (defsubr): Use XSETTYPED_PVECTYPE, since Lisp_Subr is a
 special case.
 src/process.c (Fformat_network_address): Use local var for size,
 for brevity.
 src/fns.c (vector): Remove; this old hack is no longer needed.
 src/bytecode.c (exec_byte_code): Don't use XVECTOR before CHECK_VECTOR.

1 files changed, 5 insertions, 5 deletions

diff --git a/src/keymap.c b/src/keymap.c
index b3c1400a64c..dec53cbd8e1 100644
--- a/src/keymap.c
+++ b/src/keymap.c
@@ -421,7 +421,7 @@ Return PARENT.  PARENT should be nil or another keymap.  */)
                                 XCDR (XCAR (list)));
 
       if (VECTORP (XCAR (list)))
-        for (i = 0; i < XVECTOR (XCAR (list))->size; i++)
+        for (i = 0; i < XVECTOR_SIZE (XCAR (list)); i++)
           if (CONSP (XVECTOR (XCAR (list))->contents[i]))
             fix_submap_inheritance (keymap, make_number (i),
                                     XVECTOR (XCAR (list))->contents[i]);
@@ -2337,7 +2337,7 @@ spaces are put between sequence elements, etc.  */)
   if (STRINGP (list))
     size = SCHARS (list);
   else if (VECTORP (list))
-    size = XVECTOR (list)->size;
+    size = XVECTOR_SIZE (list);
   else if (CONSP (list))
     size = XINT (Flength (list));
   else
@@ -3257,7 +3257,7 @@ key             binding\n\
 
           elt = XCAR (list);
           prefix = Fcar (elt);
-          if (XVECTOR (prefix)->size >= 1)
+          if (XVECTOR_SIZE (prefix) >= 1)
             {
               tem = Faref (prefix, make_number (0));
               if (EQ (tem, Qmenu_bar))
@@ -3300,7 +3300,7 @@ key             binding\n\
           /* If the sequence by which we reach this keymap is zero-length,
              then the shadow map for this keymap is just SHADOW.  */
           if ((STRINGP (prefix) && SCHARS (prefix) == 0)
-              || (VECTORP (prefix) && XVECTOR (prefix)->size == 0))
+              || (VECTORP (prefix) && XVECTOR_SIZE (prefix) == 0))
             ;
           /* If the sequence by which we reach this keymap actually has
              some elements, then the sequence's definition in SHADOW is
@@ -3748,7 +3748,7 @@ describe_vector (vector, prefix, args, elt_describer,
   if (CHAR_TABLE_P (vector))
     stop = MAX_5_BYTE_CHAR + 1, to = MAX_CHAR + 1;
   else
-    stop = to = XVECTOR (vector)->size;
+    stop = to = XVECTOR_SIZE (vector);
 
   for (i = from; ; i++)
     {