diff --git a/.gitignore b/.gitignore
index 7ead3a81f506b0..6ec036860829d4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -58,6 +58,7 @@ lcov*.info
 /*-fake.rb
 /*.dll
 /*.exe
+/*.ilk
 /*.res
 /*.pc
 /*.rc
diff --git a/NEWS.md b/NEWS.md
index 004e151df07bd9..3ba44ddeb87e75 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -131,7 +131,7 @@ releases.
 * pstore 0.2.1
   * 0.2.0 to [v0.2.1][pstore-v0.2.1]
 * rdoc 8.0.0
-  * 7.0.3 to [v7.0.4][rdoc-v7.0.4], [v7.1.0][rdoc-v7.1.0], [v7.2.0][rdoc-v7.2.0]
+  * 7.0.3 to [v7.0.4][rdoc-v7.0.4], [v7.1.0][rdoc-v7.1.0], [v7.2.0][rdoc-v7.2.0], [v8.0.0][rdoc-v8.0.0]
 * win32ole 1.9.3
   * 1.9.2 to [v1.9.3][win32ole-v1.9.3]
 * irb 1.18.0
@@ -286,6 +286,7 @@ A lot of work has gone into making Ractors more stable, performant, and usable.
 [rdoc-v7.0.4]: https://github.com/ruby/rdoc/releases/tag/v7.0.4
 [rdoc-v7.1.0]: https://github.com/ruby/rdoc/releases/tag/v7.1.0
 [rdoc-v7.2.0]: https://github.com/ruby/rdoc/releases/tag/v7.2.0
+[rdoc-v8.0.0]: https://github.com/ruby/rdoc/releases/tag/v8.0.0
 [win32ole-v1.9.3]: https://github.com/ruby/win32ole/releases/tag/v1.9.3
 [irb-v1.17.0]: https://github.com/ruby/irb/releases/tag/v1.17.0
 [irb-v1.18.0]: https://github.com/ruby/irb/releases/tag/v1.18.0
diff --git a/ext/json/parser/parser.c b/ext/json/parser/parser.c
index a6154c83ec52de..a60f6a3c95511b 100644
--- a/ext/json/parser/parser.c
+++ b/ext/json/parser/parser.c
@@ -2625,11 +2625,16 @@ static VALUE cResumableParser_partial_value_body(VALUE self)
         missing_object_value = 1;
     }
 
-    // Copy the value stack as we need to mutate it.
+    // Copy the value stack as we need to mutate it. The collapse loop folds each
+    // open container by popping its entries and pushing the single result, so a
+    // parent always reclaims its child's slot; head exceeds its live size by at
+    // most one, either for the missing-value placeholder pushed below or for the
+    // result of folding an empty innermost container. That one spare slot keeps
+    // rvalue_stack_push from growing (reallocating) this ALLOCV buffer.
     long capa = parser.value_stack.head;
-    parser.value_stack.capa = (capa + missing_object_value);
-    VALUE tmpbuf, *value_stack_buffer = ALLOCV_N(VALUE, tmpbuf, capa + missing_object_value);
-    MEMCPY(value_stack_buffer, parser.value_stack.ptr, VALUE, parser.value_stack.capa);
+    parser.value_stack.capa = capa + 1;
+    VALUE tmpbuf, *value_stack_buffer = ALLOCV_N(VALUE, tmpbuf, parser.value_stack.capa);
+    MEMCPY(value_stack_buffer, parser.value_stack.ptr, VALUE, capa);
     parser.value_stack.ptr = value_stack_buffer;
 
     JSON_ParserState *state = &parser.state;
diff --git a/gc/mmtk/mmtk.c b/gc/mmtk/mmtk.c
index 39b6fb4c87f094..d996b923525430 100644
--- a/gc/mmtk/mmtk.c
+++ b/gc/mmtk/mmtk.c
@@ -965,8 +965,7 @@ size_t
 rb_gc_impl_heap_id_for_size(void *objspace_ptr, size_t size)
 {
     for (int i = 0; i < MMTK_HEAP_COUNT; i++) {
-        if (size == heap_sizes[i]) return i;
-        if (size < heap_sizes[i])  return i;
+        if (size <= heap_sizes[i]) return i;
     }
 
     rb_bug("size too big");
diff --git a/spec/bundler/bundler/mirror_spec.rb b/spec/bundler/bundler/mirror_spec.rb
index ba1c6ed413daf8..34e61644fdf031 100644
--- a/spec/bundler/bundler/mirror_spec.rb
+++ b/spec/bundler/bundler/mirror_spec.rb
@@ -298,15 +298,13 @@
 
   context "with a listening TCP Server" do
     def with_server_and_mirror
-      server = TCPServer.new("0.0.0.0", 0)
-      mirror = Bundler::Settings::Mirror.new("http://0.0.0.0:#{server.addr[1]}", 1)
+      server = TCPServer.new("127.0.0.1", 0)
+      mirror = Bundler::Settings::Mirror.new("http://127.0.0.1:#{server.addr[1]}", 1)
       yield server, mirror
       server.close unless server.closed?
     end
 
     it "probes the server correctly" do
-      skip "obscure error" if Gem.win_platform?
-
       with_server_and_mirror do |server, mirror|
         expect(server.closed?).to be_falsey
         expect(probe.replies?(mirror)).to be_truthy
diff --git a/spec/bundler/install/git_spec.rb b/spec/bundler/install/git_spec.rb
index 1172d661ae69e2..57c4743e85f9e9 100644
--- a/spec/bundler/install/git_spec.rb
+++ b/spec/bundler/install/git_spec.rb
@@ -40,8 +40,6 @@
     end
 
     it "displays the ref of the gem repository when using branch~num as a ref" do
-      skip "maybe branch~num notation doesn't work on Windows' git" if Gem.win_platform?
-
       build_git "foo", "1.0", path: lib_path("foo")
       rev = revision_for(lib_path("foo"))[0..6]
       update_git "foo", "2.0", path: lib_path("foo"), gemspec: true
diff --git a/test/json/resumable_parser_test.rb b/test/json/resumable_parser_test.rb
index 4cc6c085dff7c3..734d6e220b769d 100644
--- a/test/json/resumable_parser_test.rb
+++ b/test/json/resumable_parser_test.rb
@@ -247,6 +247,17 @@ def test_partial_value
     assert_partial_value([1, { "a" => 1, "b" => { "c" => nil } }], '[1, { "a": 1, "b": { "c"')
   end
 
+  def test_partial_value_collapses_nested_incomplete_containers
+    # partial_value rebuilds the open containers on a scratch value stack; folding
+    # an empty inner container pushes a value, so that stack must hold more than its
+    # live size or the push reallocates the scratch buffer.
+    assert_partial_value({ "abc" => {} }, '{"abc":{"d')
+    assert_partial_value({ "a" => { "b" => { "c" => {} } } }, '{"a":{"b":{"c":{"e')
+    assert_partial_value([1, { "a" => {} }], '[1,{"a":{"d')
+    assert_partial_value({ "a" => [1, { "b" => [2, { "c" => nil }] }] }, '{"a":[1,{"b":[2,{"c"')
+    assert_partial_value([1, [2, [3, { "x" => nil }]]], '[1,[2,[3,{"x":[')
+  end
+
   def test_partial_value_issue_1005
     data = <<~JSON
       [
diff --git a/test/ruby/test_settracefunc.rb b/test/ruby/test_settracefunc.rb
index b4af8fa98625b8..95fc7f45536217 100644
--- a/test/ruby/test_settracefunc.rb
+++ b/test/ruby/test_settracefunc.rb
@@ -26,6 +26,19 @@ def target_thread?
     Thread.current == @target_thread
   end
 
+  # Reject trace events from other code interrupting this thread, such as
+  # finalizers of objects left by other tests (e.g. Tempfile's), whose
+  # frames are pushed on top of the interrupted frame of this file. An
+  # event is ours iff the innermost frame, ignoring core methods written
+  # in Ruby (<internal:*> such as Kernel#tap), belongs to this file.
+  #
+  # +locations+ must be the caller_locations captured directly in the
+  # trace handler; capturing it here would add this method's own frame.
+  def event_from_this_file?(locations)
+    innermost = locations.drop_while{|loc| loc.path.start_with?("<internal:")}.first
+    innermost&.path == __FILE__
+  end
+
   def test_c_call
     events = []
     name = "#{self.class}\##{__method__}"
@@ -1577,6 +1590,7 @@ def test_define_method_on_return
     obj = C11492.new
     TracePoint.new(:call, :return){|tp|
       next unless target_thread?
+      next unless event_from_this_file?(caller_locations)
       events << [tp.event, tp.method_id]
     }.enable{
       obj.foo_return
@@ -1588,6 +1602,7 @@ def test_define_method_on_return
     obj = C11492.new
     TracePoint.new(:call, :return){|tp|
       next unless target_thread?
+      next unless event_from_this_file?(caller_locations)
       events << [tp.event, tp.method_id]
     }.enable{
       obj.foo_break
@@ -1600,6 +1615,7 @@ def test_define_method_on_return
     begin
       set_trace_func(lambda{|event, file, lineno, mid, binding, klass|
         next unless target_thread?
+        next unless event_from_this_file?(caller_locations)
         case event
         when 'call', 'return'
           events << [event, mid]
@@ -1617,6 +1633,7 @@ def test_define_method_on_return
     begin
       set_trace_func(lambda{|event, file, lineno, mid, binding, klass|
         next unless target_thread?
+        next unless event_from_this_file?(caller_locations)
         case event
         when 'call', 'return'
           events << [event, mid]
@@ -1904,14 +1921,7 @@ def test_tracepoint_callee_id
     events = []
     capture_events = Proc.new{|tp|
       next unless target_thread?
-      # Skip events from other code interrupting this thread, such as
-      # finalizers of objects left by other tests (e.g. Tempfile's),
-      # whose frames are pushed on top of the interrupted frame of this
-      # file. The event is ours iff the innermost frame, ignoring core
-      # methods written in Ruby (e.g. Kernel#tap in <internal:kernel>),
-      # belongs to this file.
-      innermost = caller_locations.drop_while{|loc| loc.path.start_with?("<internal:")}.first
-      next unless innermost&.path == __FILE__
+      next unless event_from_this_file?(caller_locations)
       events << [tp.event, tp.method_id, tp.callee_id]
     }
 
@@ -2968,6 +2978,10 @@ def test_tracepoint_thread_end_with_exception
     assert_kind_of(Thread, target_thread)
   end
 
+  private def finalized(done)
+    proc {done[0] = true}
+  end
+
   def test_tracepoint_garbage_collected_when_disable
     before_count_stat = 0
     before_count_objspace = 0
@@ -2982,18 +2996,17 @@ def test_tracepoint_garbage_collected_when_disable
     tp.enable
     Class.inspect # c_call, c_return invoked
     tp.disable
-    tp_id = tp.object_id
+    done = [false]
+    ObjectSpace.define_finalizer(tp, finalized(done))
     tp = nil
 
     gc_times = 0
     gc_max_retries = 10
-    EnvUtil.suppress_warning do
-      until (ObjectSpace._id2ref(tp_id) rescue nil).nil?
-        GC.start
-        gc_times += 1
-        if gc_times == gc_max_retries
-          break
-        end
+    until done[0]
+      GC.start
+      gc_times += 1
+      if gc_times == gc_max_retries
+        break
       end
     end
     return if gc_times == gc_max_retries
@@ -3002,12 +3015,12 @@ def test_tracepoint_garbage_collected_when_disable
     TracePoint.stat.each do |v|
       after_count_stat += 1
     end
-    assert after_count_stat <= before_count_stat
+    assert_operator after_count_stat, :<=, before_count_stat
     after_count_objspace = 0
     ObjectSpace.each_object(TracePoint) do
       after_count_objspace += 1
     end
-    assert after_count_objspace <= before_count_objspace
+    assert_operator after_count_objspace, :<=, before_count_objspace
   end
 
   def test_tp_ractor_local_untargeted
@@ -3101,7 +3114,9 @@ def foo
   def test_tracepoints_not_disabled_by_ractor_gc
     assert_ractor("#{<<~"begin;"}\n#{<<~'end;'}")
     begin;
-    $-w = nil # uses ObjectSpace._id2ref
+    def finalized(done)
+      proc {done[0] = true}
+    end
     def hi = "hi"
     greetings = 0
     tp_target = TracePoint.new(:call) do |tp|
@@ -3117,12 +3132,13 @@ def hi = "hi"
 
     r = Ractor.new { 10 }
     r.join
-    ractor_id = r.object_id
+    done = [false]
+    ObjectSpace.define_finalizer(r, finalized(done))
     r = nil # allow gc for ractor
     gc_max_retries = 15
     gc_times = 0
     # force GC of ractor (or try, because we have a conservative GC)
-    until (ObjectSpace._id2ref(ractor_id) rescue nil).nil?
+    until done[0]
       GC.start
       gc_times += 1
       if gc_times == gc_max_retries
@@ -3140,11 +3156,7 @@ def hi = "hi"
     tp_target.disable
     tp_global.disable
     assert_equal 5, greetings
-    if gc_times == gc_max_retries # _id2ref never raised
-      assert_equal 6, raises
-    else
-      assert_equal 7, raises
-    end
+    assert_equal 6, raises
     end;
   end
 
diff --git a/test/rubygems/test_gem_compact_index_client_cache_file.rb b/test/rubygems/test_gem_compact_index_client_cache_file.rb
index c782f6336165ee..193ae327e9c24b 100644
--- a/test/rubygems/test_gem_compact_index_client_cache_file.rb
+++ b/test/rubygems/test_gem_compact_index_client_cache_file.rb
@@ -123,13 +123,12 @@ def test_commit_after_close_raises
   end
 
   def test_write_preserves_permissions
-    pend "chmod is unreliable on Windows" if Gem.win_platform?
-
     @path.binwrite "old"
-    @path.chmod 0o600
+    @path.chmod 0o400
 
     CacheFile.write(@path, "new")
 
-    assert_equal 0o600, @path.stat.mode & 0o777
+    assert_equal "new", @path.binread
+    assert_equal 0, @path.stat.mode & 0o200, "expected CacheFile.write to preserve the original read-only permission"
   end
 end
diff --git a/test/rubygems/test_gem_specification.rb b/test/rubygems/test_gem_specification.rb
index 79be0c996d2371..c63e68be47dd77 100644
--- a/test/rubygems/test_gem_specification.rb
+++ b/test/rubygems/test_gem_specification.rb
@@ -3159,14 +3159,14 @@ def test_validate_require_paths_with_invalid_types
   end
 
   def test_validate_files
-    pend "test_validate_files skipped on MS Windows (symlink)" if Gem.win_platform?
+    pend "Symlinks not supported or not enabled" unless symlink_supported?
     util_setup_validate
 
     @a1.files += ["lib", "lib2"]
     @a1.extensions << "ext/a/extconf.rb"
 
     Dir.chdir @tempdir do
-      FileUtils.ln_s "lib/code.rb", "lib2" unless vc_windows?
+      FileUtils.ln_s "lib/code.rb", "lib2"
 
       use_ui @ui do
         @a1.validate
diff --git a/tool/lib/_tmpdir.rb b/tool/lib/_tmpdir.rb
index f4ac29ffb64fd9..ec3189f16f94c5 100644
--- a/tool/lib/_tmpdir.rb
+++ b/tool/lib/_tmpdir.rb
@@ -110,4 +110,5 @@ def list_tree(parent, indent = "", &block)
   end
 }
 
-ENV["TMPDIR"] = ENV["SPEC_TEMP_DIR"] = ENV["GEM_TEST_TMPDIR"] = tmpdir
+ENV["TMPDIR"] = ENV["GEM_TEST_TMPDIR"] = tmpdir
+ENV["SPEC_TEMP_DIR"] = File.join(tmpdir, "spec")