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[Emacs-diffs] master 81e7eef: Fix bignum bugs with nth, elt, =
From: |
Paul Eggert |
Subject: |
[Emacs-diffs] master 81e7eef: Fix bignum bugs with nth, elt, = |
Date: |
Tue, 21 Aug 2018 14:41:59 -0400 (EDT) |
branch: master
commit 81e7eef8224c8a99a207b7a7b9dae1d598392ef7
Author: Paul Eggert <address@hidden>
Commit: Paul Eggert <address@hidden>
Fix bignum bugs with nth, elt, =
* src/bytecode.c (exec_byte_code): Support bignums
when implementing nth, elt, and =.
* src/lisp.h (SMALL_LIST_LEN_MAX): New constant.
* src/fns.c (Fnthcdr): Use it.
(Felt): Do not reject bignum indexes.
---
src/bytecode.c | 39 +++++++++++++--------------------------
src/fns.c | 5 ++---
src/lisp.h | 5 +++++
3 files changed, 20 insertions(+), 29 deletions(-)
diff --git a/src/bytecode.c b/src/bytecode.c
index b27fa7c..17457fc 100644
--- a/src/bytecode.c
+++ b/src/bytecode.c
@@ -832,13 +832,14 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector,
Lisp_Object maxdepth,
CASE (Bnth):
{
Lisp_Object v2 = POP, v1 = TOP;
- CHECK_FIXNUM (v1);
- for (EMACS_INT n = XFIXNUM (v1); 0 < n && CONSP (v2); n--)
+ if (RANGED_FIXNUMP (0, v1, SMALL_LIST_LEN_MAX))
{
- v2 = XCDR (v2);
- rarely_quit (n);
+ for (EMACS_INT n = XFIXNUM (v1); 0 < n && CONSP (v2); n--)
+ v2 = XCDR (v2);
+ TOP = CAR (v2);
}
- TOP = CAR (v2);
+ else
+ TOP = Fnth (v1, v2);
NEXT;
}
@@ -985,15 +986,8 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector,
Lisp_Object maxdepth,
CASE (Beqlsign):
{
- Lisp_Object v2 = POP, v1 = TOP;
- if (FLOATP (v1) || FLOATP (v2))
- TOP = arithcompare (v1, v2, ARITH_EQUAL);
- else
- {
- CHECK_FIXNUM_OR_FLOAT_COERCE_MARKER (v1);
- CHECK_FIXNUM_OR_FLOAT_COERCE_MARKER (v2);
- TOP = EQ (v1, v2) ? Qt : Qnil;
- }
+ Lisp_Object v1 = POP;
+ TOP = arithcompare (TOP, v1, ARITH_EQUAL);
NEXT;
}
@@ -1264,23 +1258,16 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object
vector, Lisp_Object maxdepth,
CASE (Belt):
{
- if (CONSP (TOP))
+ Lisp_Object v2 = POP, v1 = TOP;
+ if (CONSP (v1) && RANGED_FIXNUMP (0, v2, SMALL_LIST_LEN_MAX))
{
- /* Exchange args and then do nth. */
- Lisp_Object v2 = POP, v1 = TOP;
- CHECK_FIXNUM (v2);
+ /* Like the fast case for Bnth, but with args reversed. */
for (EMACS_INT n = XFIXNUM (v2); 0 < n && CONSP (v1); n--)
- {
- v1 = XCDR (v1);
- rarely_quit (n);
- }
+ v1 = XCDR (v1);
TOP = CAR (v1);
}
else
- {
- Lisp_Object v1 = POP;
- TOP = Felt (TOP, v1);
- }
+ TOP = Felt (v1, v2);
NEXT;
}
diff --git a/src/fns.c b/src/fns.c
index 9d68101..b368ffd 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -1418,7 +1418,7 @@ DEFUN ("nthcdr", Fnthcdr, Snthcdr, 2, 2, 0,
num = XFIXNUM (n);
/* Speed up small lists by omitting circularity and quit checking. */
- if (num < 128)
+ if (num <= SMALL_LIST_LEN_MAX)
{
for (; 0 < num; num--, tail = XCDR (tail))
if (! CONSP (tail))
@@ -1503,9 +1503,8 @@ N counts from zero. If LIST is not that long, nil is
returned. */)
DEFUN ("elt", Felt, Selt, 2, 2, 0,
doc: /* Return element of SEQUENCE at index N. */)
- (register Lisp_Object sequence, Lisp_Object n)
+ (Lisp_Object sequence, Lisp_Object n)
{
- CHECK_FIXNUM (n);
if (CONSP (sequence) || NILP (sequence))
return Fcar (Fnthcdr (n, sequence));
diff --git a/src/lisp.h b/src/lisp.h
index 8f48a33..c5593b2 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -4694,6 +4694,11 @@ enum
Lisp_String)) \
: make_unibyte_string (str, len))
+/* The maximum length of "small" lists, as a heuristic. These lists
+ are so short that code need not check for cycles or quits while
+ traversing. */
+enum { SMALL_LIST_LEN_MAX = 127 };
+
/* Loop over conses of the list TAIL, signaling if a cycle is found,
and possibly quitting after each loop iteration. In the loop body,
set TAIL to the current cons. If the loop exits normally,
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