nobu	2017-02-03 15:11:32 +0900 (Fri, 03 Feb 2017)

  New Revision: 57509

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=57509

  Log:
    internal.h: fix r57507
    
    * internal.h (rb_overflowed_fix_to_int): invert sign bit.  should
      not set LSB of fixnum value, which is always set, to MSB.

  Modified files:
    trunk/internal.h
Index: internal.h
===================================================================
--- internal.h	(revision 57508)
+++ internal.h	(revision 57509)
@@ -348,10 +348,10 @@ VALUE rb_int128t2big(int128_t n); https://github.com/ruby/ruby/blob/trunk/internal.h#L348
 
 #define ST2FIX(h) LONG2FIX((long)(h))
 
-static inline unsigned long
-rb_ulong_rotate_right(unsigned long x)
+static inline long
+rb_overflowed_fix_to_int(long x)
 {
-    return (x >> 1) | (x << (SIZEOF_LONG * CHAR_BIT - 1));
+    return (long)((unsigned long)(x >> 1) ^ (1LU << (SIZEOF_LONG * CHAR_BIT - 1)));
 }
 
 static inline VALUE
@@ -368,7 +368,7 @@ rb_fix_plus_fix(VALUE x, VALUE y) https://github.com/ruby/ruby/blob/trunk/internal.h#L368
      *     and it equals to `(z<<63)|(z>>1)` == `ror(z)`.
      */
     if (__builtin_add_overflow((long)x, (long)y-1, &lz)) {
-	return rb_int2big(rb_ulong_rotate_right((unsigned long)lz));
+	return rb_int2big(rb_overflowed_fix_to_int(lz));
     }
     else {
 	return (VALUE)lz;
@@ -385,7 +385,7 @@ rb_fix_minus_fix(VALUE x, VALUE y) https://github.com/ruby/ruby/blob/trunk/internal.h#L385
 #ifdef HAVE_BUILTIN___BUILTIN_SUB_OVERFLOW
     long lz;
     if (__builtin_sub_overflow((long)x, (long)y-1, &lz)) {
-	return rb_int2big(rb_ulong_rotate_right((unsigned long)lz));
+	return rb_int2big(rb_overflowed_fix_to_int(lz));
     }
     else {
 	return (VALUE)lz;

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