rhe	2017-11-02 15:30:18 +0900 (Thu, 02 Nov 2017)

  New Revision: 60611

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=60611

  Log:
    bignum.c: avoid use of uninitialized value in Integer.sqrt
    
    This is a follow-up fix to r57713. estimate_initial_sqrt() didn't
    initialize BDIGITs except the topmost two, letting Integer.sqrt return
    wrong result in the fast path, such as for (1<<504).

  Modified files:
    trunk/bignum.c
Index: bignum.c
===================================================================
--- bignum.c	(revision 60610)
+++ bignum.c	(revision 60611)
@@ -6830,6 +6830,7 @@ estimate_initial_sqrt(VALUE *xp, const s https://github.com/ruby/ruby/blob/trunk/bignum.c#L6830
     if (rshift >= 0) {
 	d <<= rshift;
     }
+    BDIGITS_ZERO(xds, xn-2);
     bdigitdbl2bary(&xds[xn-2], 2, d);
 
     if (!lowbits) return NULL; /* special case, exact result */

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