Make logb handle bignums

* src/floatfns.c (Flogb): Handle bignums.
* test/src/floatfns-tests.el (bignum-logb): New test.

1 files changed, 4 insertions, 1 deletions

diff --git a/src/floatfns.c b/src/floatfns.c
index 6d7fc1452d3..9a5f0a3ad2f 100644
--- a/src/floatfns.c
+++ b/src/floatfns.c
@@ -328,7 +328,7 @@ This is the same as the exponent of a float.  */)
   (Lisp_Object arg)
 {
   EMACS_INT value;
-  CHECK_FIXNUM_OR_FLOAT (arg);
+  CHECK_NUMBER (arg);
 
   if (FLOATP (arg))
     {
@@ -345,8 +345,11 @@ This is the same as the exponent of a float.  */)
       else
         value = MOST_POSITIVE_FIXNUM;
     }
+  else if (BIGNUMP (arg))
+    value = mpz_sizeinbase (XBIGNUM (arg)->value, 2) - 1;
   else
     {
+      eassert (FIXNUMP (arg));
       EMACS_INT i = eabs (XINT (arg));
       value = (i == 0
                ? MOST_NEGATIVE_FIXNUM