>From 68a58397370381fd9b5d08f5cc16a5afa2b5fd26 Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Tue, 24 Mar 2015 11:42:53 -0700 Subject: [PATCH] Fix minor ldexp issues * doc/lispref/numbers.texi (Float Basics): Improve ldexp documentation. * src/floatfns.c (Fldexp): Require 2 args. Avoid undefined behavior if the exponent is out of 'int' range. Improve documentation. Fixes: bug#20185 --- doc/lispref/ChangeLog | 4 ++++ doc/lispref/numbers.texi | 12 +++++++++--- src/ChangeLog | 7 +++++++ src/floatfns.c | 10 +++++----- 4 files changed, 25 insertions(+), 8 deletions(-) diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog index a546306..9b1bbb3 100644 --- a/doc/lispref/ChangeLog +++ b/doc/lispref/ChangeLog @@ -1,3 +1,7 @@ +2015-03-24 Paul Eggert + + * numbers.texi (Float Basics): Improve ldexp documentation. + 2015-03-23 Eli Zaretskii * commands.texi (Event Input Misc): Fix incorrect usage of @code. diff --git a/doc/lispref/numbers.texi b/doc/lispref/numbers.texi index 8d1d3a7..7b4a0a6 100644 --- a/doc/lispref/numbers.texi +++ b/doc/lispref/numbers.texi @@ -265,9 +265,15 @@ If @var{x} is a NaN, then @var{s} is also a NaN@. If @var{x} is zero, then @var{e} is 0. @end defun -@defun ldexp sig &optional exp -This function returns a floating-point number corresponding to the -significand @var{sig} and exponent @var{exp}. +@defun ldexp s e +Given a numeric significand @var{s} and an integer exponent @var{e}, +this function returns the floating point number +@ifnottex +@var{s} * 2**@var{e}. +@end ifnottex +@tex +@math{s 2^e}. +@end tex @end defun @defun copysign x1 x2 diff --git a/src/ChangeLog b/src/ChangeLog index 815c117..23f125c 100644 --- a/src/ChangeLog +++ b/src/ChangeLog @@ -1,3 +1,10 @@ +2015-03-24 Paul Eggert + + Fix minor ldexp issues + * floatfns.c (Fldexp): Require 2 args. Avoid undefined behavior + if the exponent is out of 'int' range. Improve documentation. + Fixes: bug#20185 + 2015-03-24 Daniel Colascione * process.c (Fprocess_running_child_p): Return number identifier of diff --git a/src/floatfns.c b/src/floatfns.c index c68b9bd..072e857 100644 --- a/src/floatfns.c +++ b/src/floatfns.c @@ -185,14 +185,14 @@ If X is zero, both parts (SGNFCAND and EXP) are zero. */) return Fcons (make_float (sgnfcand), make_number (exponent)); } -DEFUN ("ldexp", Fldexp, Sldexp, 1, 2, 0, - doc: /* Construct number X from significand SGNFCAND and exponent EXP. -Returns the floating point value resulting from multiplying SGNFCAND -(the significand) by 2 raised to the power of EXP (the exponent). */) +DEFUN ("ldexp", Fldexp, Sldexp, 2, 2, 0, + doc: /* Return X * 2**EXP, as a floating point number. +EXP must be an integer. */) (Lisp_Object sgnfcand, Lisp_Object exponent) { CHECK_NUMBER (exponent); - return make_float (ldexp (XFLOATINT (sgnfcand), XINT (exponent))); + int e = min (max (INT_MIN, XINT (exponent)), INT_MAX); + return make_float (ldexp (XFLOATINT (sgnfcand), e)); } DEFUN ("exp", Fexp, Sexp, 1, 1, 0, -- 2.1.0