hash: keep fstrings of tainted strings for string keys

The same hash keys may be loaded from tainted data sources
frequently (e.g. parsing headers from socket or loading
YAML data from a file).  If a non-tainted fstring already
exists (because the application expects the hash key),
cache and deduplicate the tainted version in the new
tainted_frozen_strings table.

For non-embedded strings, this also allows sharing with the
underlying malloc-ed data.

* vm_core.h (rb_vm_struct): add tainted_frozen_strings
* vm.c (ruby_vm_destruct): free tainted_frozen_strings
  (Init_vm_objects): initialize tainted_frozen_strings
  (rb_vm_tfstring_table): accessor for tainted_frozen_strings
* internal.h: declare rb_fstring_existing, rb_vm_tfstring_table
* hash.c (fstring_existing_str): remove (moved to string.c)
  (hash_aset_str): use rb_fstring_existing
* string.c (rb_fstring_existing): new, based on fstring_existing_str
  (tainted_fstr_update): new
  (rb_fstring_existing0): new, based on fstring_existing_str
  (rb_tainted_fstring_existing): new, special case for tainted strings
  (rb_str_free): delete from tainted_frozen_strings table
* test/ruby/test_optimization.rb (test_hash_reuse_fstring): new test
  [ruby-core:82012] [Bug #13737]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59354 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 31 insertions, 0 deletions

diff --git a/test/ruby/test_optimization.rb b/test/ruby/test_optimization.rb
index 2d0eec02fd..0d14c9c932 100644
--- a/test/ruby/test_optimization.rb
+++ b/test/ruby/test_optimization.rb
@@ -181,6 +181,37 @@ class TestRubyOptimization < Test::Unit::TestCase
     assert_redefine_method('Hash', 'empty?', 'assert_nil({}.empty?); assert_nil({1=>1}.empty?)')
   end
 
+  def test_hash_reuse_fstring
+    embed = -'h e l l o'
+    shared = -'this string is too long to be embedded and should be shared'
+    assert_not_equal GC::INTERNAL_CONSTANTS[:RVALUE_SIZE],
+                     ObjectSpace.memsize_of(shared),
+                     'update this test if string embedding changed'
+
+    [ embed, shared ].each do |exp|
+      key = exp.split(' ').join(' ')
+      h = {}
+      h[key] = true
+      assert_not_same key, h.keys[0]
+      assert_predicate h.keys[0], :frozen?
+      assert_same exp, h.keys[0]
+
+      h1 = {}
+      h2 = {}
+      key.taint
+      h1[key] = true
+      h2[key] = true
+      k1 = h1.keys[0]
+      k2 = h2.keys[0]
+      assert_same k1, k2
+      assert_predicate k1, :tainted?
+
+      assert_equal GC::INTERNAL_CONSTANTS[:RVALUE_SIZE],
+                   ObjectSpace.memsize_of(k1),
+                   'tainted string should share with untainted fstring'
+    end
+  end
+
   def test_hash_aref_with
     h = { "foo" => 1 }
     assert_equal 1, h["foo"]