From 025adce2cf43f4ce9f3c543c1b8973541e1414d2 Mon Sep 17 00:00:00 2001
From: Tom Tromey <tom@tromey.com>
Date: Thu, 5 Jul 2018 13:19:32 -0600
Subject: [PATCH] Make abs handle bignums

* src/floatfns.c (Fabs): Handle bignums.
* test/src/floatfns-tests.el (bignum-abs): New test.
---
 src/floatfns.c             | 19 +++++++++++++++++--
 test/src/floatfns-tests.el |  4 ++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/src/floatfns.c b/src/floatfns.c
index bd3f2dec80a..6d7fc1452d3 100644
--- a/src/floatfns.c
+++ b/src/floatfns.c
@@ -275,9 +275,24 @@ DEFUN ("abs", Fabs, Sabs, 1, 1, 0,
        doc: /* Return the absolute value of ARG.  */)
   (register Lisp_Object arg)
 {
-  CHECK_FIXNUM_OR_FLOAT (arg);
+  CHECK_NUMBER (arg);
 
-  if (FLOATP (arg))
+  if (BIGNUMP (arg))
+    {
+      mpz_t val;
+      mpz_init (val);
+      mpz_abs (val, XBIGNUM (arg)->value);
+      arg = make_number (val);
+      mpz_clear (val);
+    }
+  else if (FIXNUMP (arg) && XINT (arg) == MOST_NEGATIVE_FIXNUM)
+    {
+      mpz_t val;
+      mpz_init_set_si (val, - MOST_NEGATIVE_FIXNUM);
+      arg = make_number (val);
+      mpz_clear (val);
+    }
+  else if (FLOATP (arg))
     arg = make_float (fabs (XFLOAT_DATA (arg)));
   else if (XINT (arg) < 0)
     XSETINT (arg, - XINT (arg));
diff --git a/test/src/floatfns-tests.el b/test/src/floatfns-tests.el
index c87445b6bd2..0911ff46515 100644
--- a/test/src/floatfns-tests.el
+++ b/test/src/floatfns-tests.el
@@ -38,4 +38,8 @@
   (should (eql (float (+ most-positive-fixnum 1))
                (+ (float most-positive-fixnum) 1))))
 
+(ert-deftest bignum-abs ()
+  (should (= most-positive-fixnum
+             (- (abs most-negative-fixnum) 1))))
+
 (provide 'floatfns-tests)