merge revision(s) 57469,57471,57472,57503,57508: [Backport #13299]

	io.c: recycle garbage on write

	* string.c (STR_IS_SHARED_M): new flag to mark shared mulitple times
	  (STR_SET_SHARED): set STR_IS_SHARED_M
	  (rb_str_tmp_frozen_acquire, rb_str_tmp_frozen_release): new functions
	  (str_new_frozen): set/unset STR_IS_SHARED_M as appropriate
	* internal.h: declare new functions
	* io.c (fwrite_arg, fwrite_do, fwrite_end): new
	  (io_fwrite): use new functions

	Introduce rb_str_tmp_frozen_acquire and rb_str_tmp_frozen_release
	to manage a hidden, frozen string.  Reuse one bit of the embed
	length for shared strings as STR_IS_SHARED_M to indicate a string
	has been shared multiple times.  In the common case, the string
	is only shared once so the object slot can be reclaimed immediately.

	minimum results in each 3 measurements. (time and size)

	Execution time (sec)
	name                            trunk   built
	io_copy_stream_write            0.682   0.254
	io_copy_stream_write_socket     1.225   0.751

	Speedup ratio: compare with the result of `trunk' (greater is better)
	name    built
	io_copy_stream_write            2.680
	io_copy_stream_write_socket     1.630

	Memory usage (last size) (B)
	name                            trunk           built
	io_copy_stream_write            95436800.000    6512640.000
	io_copy_stream_write_socket     117628928.000   7127040.000

	Memory consuming ratio (size) with the result of `trunk' (greater is better)
	name    built
	io_copy_stream_write            14.654
	io_copy_stream_write_socket     16.505
	string.c (rb_str_tmp_frozen_release): release embedded strings

	Handle the embedded case first, since we may have an embedded
	duplicate and non-embedded original string.

	* string.c (rb_str_tmp_frozen_release): handled embedded strings
	* test/ruby/test_io.rb (test_write_no_garbage): new test
	  [ruby-core:78898] [Bug #13085]
	io.c (rb_io_syswrite): avoid leaving garbage after write

	As with IO#write, IO#syswrite also generates garbage which can
	be harmful in hand-coded read-write loops.

	* io.c (swrite_arg, swrite_do, swrite_end): new
	  (rb_io_syswrite): use new functions to cleanup garbage
	  [ruby-core:78898] [Bug #13085]
	Add class name to assert messages
	io.c: remove rb_ensure usage for rb_str_tmp_frozen_* calls

	Using rb_ensure pessimizes the common case and makes the code
	more difficult to read and follow.  If we hit an exceptions
	during write, just let the GC handle cleanup as the exception
	is already bad for garbage.

	* io.c (io_fwrite): call rb_str_tmp_frozen{acquire,release} directly
	  (rb_io_syswrite): ditto
	  (fwrite_do, fwrite_end, swrite_do, swrite_end): remove

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_4@57941 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 18 insertions, 0 deletions

diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index a6ab981a9c..61dfba3180 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -3508,5 +3508,23 @@ __END__
       end
       end;
     end
+
+    def test_write_no_garbage
+      res = {}
+      ObjectSpace.count_objects(res) # creates strings on first call
+      [ 'foo'.b, '*' * 24 ].each do |buf|
+        with_pipe do |r, w|
+          before = ObjectSpace.count_objects(res)[:T_STRING]
+          n = w.write(buf)
+          s = w.syswrite(buf)
+          after = ObjectSpace.count_objects(res)[:T_STRING]
+          assert_equal before, after,
+            'no strings left over after write [ruby-core:78898] [Bug #13085]'
+          assert_not_predicate buf, :frozen?, 'no inadvertant freeze'
+          assert_equal buf.bytesize, n, 'IO#write wrote expected size'
+          assert_equal s, n, 'IO#syswrite wrote expected size'
+        end
+      end
+    end
   end
 end