merge revision(s) 59384: [Backport #13759]

strscan.c: fix segfault in aref

	* ext/strscan/strscan.c (strscan_aref): fix segfault after
	  get_byte or getch which do not apply regexp.
	  [ruby-core:82116] [Bug #13759]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_4@59506 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/strscan/strscan.c

@@ -1034,6 +1034,7 @@ strscan_aref(VALUE self, VALUE idx)
             idx = rb_sym2str(idx);
             /* fall through */
         case T_STRING:
+            if (!p->regex) return Qnil;
             RSTRING_GETMEM(idx, name, i);
             i = name_to_backref_number(&(p->regs), p->regex, name, name + i, rb_enc_get(idx));
             break;

test/strscan/test_stringscanner.rb

@@ -718,4 +718,14 @@ class TestStringScanner < Test::Unit::TestCase
     s.scan(/test strin/)
     assert_equal('#<StringScanner 10/16 "...strin" @ "g tes...">', s.inspect)
   end
+
+  def test_aref_without_regex
+    s = StringScanner.new('abc')
+    s.get_byte
+    assert_nil(s[:c])
+    assert_nil(s["c"])
+    s.getch
+    assert_nil(s[:c])
+    assert_nil(s["c"])
+  end
 end

version.h

@@ -1,6 +1,6 @@
 #define RUBY_VERSION "2.4.2"
 #define RUBY_RELEASE_DATE "2017-08-05"
-#define RUBY_PATCHLEVEL 171
+#define RUBY_PATCHLEVEL 172
 
 #define RUBY_RELEASE_YEAR 2017
 #define RUBY_RELEASE_MONTH 8