Fix recently-introduced ash bug

Problem reported by John Paul Adrian Glaubitz (bug#79876).
* src/data.c (Fash): Don’t assume stdc_leading_zeros, which
returns an unsigned integer of unspecified width, returns
a value narrower than EMACS_INT.  Also, don’t munge the code to
worry about stdc_leading_zeros (0); unlike GCC’s __builtin_clz,
stdc_leading_zeros works fine on 0.  And use a temporary to
avoid a cast.

1 files changed, 5 insertions, 4 deletions

diff --git a/src/data.c b/src/data.c
index fb9e1e3218d..a1861bd53d0 100644
--- a/src/data.c
+++ b/src/data.c
@@ -3532,10 +3532,10 @@ discarding bits.  */)
   CHECK_INTEGER (value);
   CHECK_INTEGER (count);
 
-  if (BASE_EQ (value, make_fixnum (0)))
-    return value;
   if (! FIXNUMP (count))
     {
+      if (BASE_EQ (value, make_fixnum (0)))
+        return value;
       if (mpz_sgn (*xbignum_val (count)) < 0)
         {
           EMACS_INT v = (FIXNUMP (value) ? XFIXNUM (value)
@@ -3563,8 +3563,9 @@ discarding bits.  */)
   else if (FIXNUMP (value))
     {
       EMACS_INT v = XFIXNUM (value);
-      if (stdc_leading_zeros ((EMACS_UINT)(v < 0 ? ~v : v)) - c
-          >= EMACS_INT_WIDTH - FIXNUM_BITS + 1)
+      EMACS_UINT uv = v < 0 ? ~v : v;
+      EMACS_INT lz = stdc_leading_zeros (uv);
+      if (EMACS_INT_WIDTH - FIXNUM_BITS < lz - c)
         return make_fixnum (v << c);
     }