Re: Some vars now limited to fixnum size. (Was: Merging bignum to master)

[Paul Eggert <eggert@cs.ucla.edu>]

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Paul Eggert wrote:
> Karl Fogel wrote:
>> My proposal would be to at least document it for `nthcdr'
> 
> It would be better to fix nthcdr so that it works on bignums

... and I did that by installing the attached patch.

Thanks for reporting the problem. It's helpful to see which functions should 
have higher priority for fixing these sorts of glitches. If you're bitten by 
similar glitches in other functions please let us know.

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From 21397837eaf0801e7b1cd4155a811a939a7667de Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Mon, 20 Aug 2018 10:24:19 -0700
Subject: [PATCH] nthcdr now works with bignums

Problem reported by Karl Fogel in:
https://lists.gnu.org/r/emacs-devel/2018-08/msg00671.html
* src/fns.c (Fnthcdr): Support bignum counts.
---
 src/fns.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/fns.c b/src/fns.c
index a11de1b082..aeb9308d22 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -1402,9 +1402,20 @@ DEFUN ("nthcdr", Fnthcdr, Snthcdr, 2, 2, 0,
        doc: /* Take cdr N times on LIST, return the result.  */)
   (Lisp_Object n, Lisp_Object list)
 {
-  CHECK_FIXNUM (n);
+  CHECK_INTEGER (n);
   Lisp_Object tail = list;
-  for (EMACS_INT num = XFIXNUM (n); 0 < num; num--)
+
+  EMACS_INT num;
+  if (FIXNUMP (n))
+    num = XFIXNUM (n);
+  else
+    {
+      num = mpz_sgn (XBIGNUM (n)->value);
+      if (0 < num)
+	num = EMACS_INT_MAX;  /* LIST cannot possibly be this long.  */
+    }
+
+  for (; 0 < num; num--)
     {
       if (! CONSP (tail))
 	{
-- 
2.17.1