[fix] potential string sharing as each_line returns shared buffer

kares · kares · commit e485ef3be2b1 · 2018-06-12T17:53:56.000+02:00
... later modification to StringIO#string might affect the line resolves GH-5203
diff --git a/core/src/main/java/org/jruby/ext/stringio/StringIO.java b/core/src/main/java/org/jruby/ext/stringio/StringIO.java
@@ -508,6 +508,7 @@ private RubyString strioSubstr(Ruby runtime, int pos, int len) {
             if (len < 0) len = 0;
 
             if (len == 0) return RubyString.newEmptyString(runtime);
+            string.setByteListShared(); // we only share the byte[] buffer but its easier this way
             return RubyString.newStringShared(runtime, stringBytes, stringByteList.getBegin() + pos, len, enc);
         }
     }
@@ -657,7 +658,7 @@ private IRubyObject getline(ThreadContext context, final IRubyObject rs, int lim
             if (limit > 0 && s + limit < e) {
                 e = ptr.enc.rightAdjustCharHead(stringBytes, s, s + limit, e);
             }
-            if (rs.isNil()) {
+            if (rs == context.nil) {
                 if (chomp) {
                     w = chompNewlineWidth(stringBytes, s, e);
                 }
diff --git a/test/jruby/test_string.rb b/test/jruby/test_string.rb
@@ -96,6 +96,17 @@ def test_count
     assert_equal(2, "abc\u{3042 3044 3046}".count("^\u3042", "^\u3044", "^\u3046", "^c"))
   end
 
+  # GH-5203
+  def test_string_buffer_sharing_in_stringio; require 'stringio'
+    zero = 0
+    strio = StringIO.new "123\nabcdefghijklmnopqrstuvxyz\n#{zero}\n"
+    ary = []; strio.each_line { |line| ary << line }
+    strio.rewind
+    strio.write('456')
+    assert_equal ["123\n", "abcdefghijklmnopqrstuvxyz\n", "0\n"], ary
+    assert_equal "456\nabcdefghijklmnopqrstuvxyz\n0\n", strio.string
+  end
+
   private
 
   def do_sub buf, e1, e2, e3

Original file line number	Diff line number	Diff line change
`@@ -508,6 +508,7 @@ private RubyString strioSubstr(Ruby runtime, int pos, int len) {`
`508`	`508`	`if (len < 0) len = 0;`
`509`	`509`
`510`	`510`	`if (len == 0) return RubyString.newEmptyString(runtime);`
	`511`	`+ string.setByteListShared(); // we only share the byte[] buffer but its easier this way`
`511`	`512`	`return RubyString.newStringShared(runtime, stringBytes, stringByteList.getBegin() + pos, len, enc);`
`512`	`513`	`}`
`513`	`514`	`}`
`@@ -657,7 +658,7 @@ private IRubyObject getline(ThreadContext context, final IRubyObject rs, int lim`
`657`	`658`	`if (limit > 0 && s + limit < e) {`
`658`	`659`	`e = ptr.enc.rightAdjustCharHead(stringBytes, s, s + limit, e);`
`659`	`660`	`}`
`660`		`- if (rs.isNil()) {`
	`661`	`+ if (rs == context.nil) {`
`661`	`662`	`if (chomp) {`
`662`	`663`	`w = chompNewlineWidth(stringBytes, s, e);`
`663`	`664`	`}`