Always allow at least double-precision bignums

Without this fix, Emacs can get into a tight loop reporting
a range error when calculating timestamps.
* doc/lispref/numbers.texi (Integer Basics):
* src/alloc.c (syms_of_alloc): Document this.
* src/bignum.c (make_bignum_bits): Always allow bignums
of at least twice the width of (u)intmax_t.

1 files changed, 7 insertions, 7 deletions

diff --git a/doc/lispref/numbers.texi b/doc/lispref/numbers.texi
index fbdd83fa86e..cae8babcb40 100644
--- a/doc/lispref/numbers.texi
+++ b/doc/lispref/numbers.texi
@@ -191,19 +191,19 @@ on 64-bit platforms.
 @cindex integer range
 @cindex number of bignum bits, limit on
 @defvar integer-width
-The value of this variable is a nonnegative integer that is an upper
-bound on the number of bits in a bignum.  Integers outside the fixnum
-range are limited to absolute values less than
+The value of this variable is a nonnegative integer that controls
+whether Emacs signals a range error when a large integer would be
+calculated.  Integers with absolute values less than
 @ifnottex
 2**@var{n},
 @end ifnottex
 @tex
 @math{2^{n}},
 @end tex
-where @var{n} is this variable's value.  Attempts to create bignums outside
-this range signal a range error.  Setting this variable
-to zero disables creation of bignums; setting it to a large number can
-cause Emacs to consume large quantities of memory if a computation
+where @var{n} is this variable's value, do not signal a range error.
+Attempts to create larger integers typically signal a range error,
+although there might be no signal if a larger integer can be created cheaply.
+Setting this variable to a large number can be costly if a computation
 creates huge integers.
 @end defvar