numeric.c: fix edge case

* numeric.c (rb_fix2str): fix edge case, accidentally generated
  wrong Fixnum from LONG_MIN.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54092 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Sun Mar 13 09:15:45 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* numeric.c (rb_fix2str): fix edge case, accidentally generated
+	  wrong Fixnum from LONG_MIN.
+
 Sat Mar 12 09:50:27 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* vm_eval.c (rb_f_catch): [DOC] fix malformed RDoc syntax, "+...+"

numeric.c

@@ -2905,7 +2905,15 @@ rb_fix2str(VALUE x, int base)
 	return rb_usascii_str_new2("0");
     }
     if (val < 0) {
-	val = -val;
+	if (val == LONG_MIN) {
+	    int last = ((int)((val = LONG_MAX) % base) + 1);
+	    *--b = ruby_digitmap[last % base];
+	    val /= base;
+	    val += last == base; /* carry */
+	}
+	else {
+	    val = -val;
+	}
 	neg = 1;
     }
     do {