April 2026 - ruby-core - ml.ruby-lang.org

[ruby-core:124840] [Ruby Bug#21883] IO::Buffer can be unlocked and freed by another thread during syscall
by hanazuki (Kasumi Hanazuki) 22 Aug '26

22 Aug '26

Issue #21883 has been reported by hanazuki (Kasumi Hanazuki). ---------------------------------------- Bug #21883: IO::Buffer can be unlocked and freed by another thread during syscall https://bugs.ruby-lang.org/issues/21883 * Author: hanazuki (Kasumi Hanazuki) * Status: Open * ruby -v: ruby 4.0.1 (2026-01-13 revision e04267a14b) +PRISM [x86_64-linux] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- ```ruby # Assume this file is on a very slow device such as NFS. io = File.open('/mnt/slowfs/slow') buf = IO::Buffer.new(100) t1 = Thread.new do buf.locked do sleep 0.5 end buf.free end t2 = Thread.new do buf.read(io) # syscall takes 1 second # When the kernal writes to the memory, buf is already freed, thus use-after-free end t1.join t2.join ``` `io_buffer_blocking_region` skips taking a lock when the buffer is already locked, but this lock may be owned by another thread and can be unlocked during the syscall. -- https://bugs.ruby-lang.org/

3 2

[ruby-core:111678] [Ruby master Feature#19315] Lazy substrings in CRuby
by Eregon (Benoit Daloze) 21 Aug '26

21 Aug '26

Issue #19315 has been reported by Eregon (Benoit Daloze). ---------------------------------------- Feature #19315: Lazy substrings in CRuby https://bugs.ruby-lang.org/issues/19315 * Author: Eregon (Benoit Daloze) * Status: Open * Priority: Normal ---------------------------------------- CRuby should implement lazy substrings, i.e., "abcdef"[1..3] must not copy bytes. Currently CRuby only reuse the char* if the substring is until the end of the buffer. But it should also work wherever the substring starts and ends. Yes, it means RSTRING_PTR() might need to allocate to \0-terminate, so be it, it's worth it. There is already code for this (`SHARABLE_MIDDLE_SUBSTRING`), but it's disabled by default and `RSTRING_PTR()` needs to be changed to deal with this. It seems a good idea to introduce a variant of `RSTRING_PTR` which doesn't guarantee \0-termination, so such callers can then use the existing bytes always without copy. There are countless workarounds for this missing optimization, all not worth and all less readable: * https://bugs.ruby-lang.org/issues/19314 * https://github.com/ruby/net-protocol/pull/14 * Manual lazy substrings which track string + index + length * More but I don't remember all now, feel free to comment or link more urls/tickets. -- https://bugs.ruby-lang.org/

10 51

[ruby-core:121627] [Ruby Feature#21264] Extract Date library from Ruby repo in the future
by hsbt (Hiroshi SHIBATA) 20 Aug '26

20 Aug '26

Issue #21264 has been reported by hsbt (Hiroshi SHIBATA). ---------------------------------------- Feature #21264: Extract Date library from Ruby repo in the future https://bugs.ruby-lang.org/issues/21264 * Author: hsbt (Hiroshi SHIBATA) * Status: Open ---------------------------------------- Note: This is not for Ruby 3.5. `Date` and `DateTime` has no primary maintainer in 10+ years. I would like to deprecate `date` via bundled gems for reducing our maintenance time especially @nobu. But `Time.prase` and `Time.strptime` are widely used now. How do we deprecate `date` library? 1. Migrate `Date._strptime`, `Date.strptime` and `Date._parse` to `Time`. The current `Date` is migrated as bundled gems. 2. Migrate `Date` to the bundled gems. `Time.parse` and `Time.strptime` warns if `date` is not found. 3. Keep the current situation 4. ... Does anyone have another idea? -- https://bugs.ruby-lang.org/

5 10

[ruby-core:116370] [Ruby master Bug#20203] `TestEnumerable` test failures with GCC 14
by vo.x (Vit Ondruch) 17 Aug '26

17 Aug '26

Issue #20203 has been reported by vo.x (Vit Ondruch). ---------------------------------------- Bug #20203: `TestEnumerable` test failures with GCC 14 https://bugs.ruby-lang.org/issues/20203 * Author: vo.x (Vit Ondruch) * Status: Open * Priority: Normal * ruby -v: ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [x86_64-linux] * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- There is ongoing mass rebuild in Fedora and that is first time GCC 14 is used and we observe test failures in `TestEnumerable`. Here are a few examples: ~~~ [ 3000/26419] TestEnumerable#test_transient_heap_sort_bymalloc_consolidate(): unaligned fastbin chunk detected ~~~ ~~~ [ 2455/26535] TestEnumerable#test_transient_heap_sort_bycorrupted size vs. prev_size in fastbins ~~~ ~~~ [ 9716/26532] TestEnumerable#test_any_with_unused_blockdouble free or corruption (fasttop) ~~~ The full logs are accessible [here](https://koji.fedoraproject.org/koji/taskinfo?taskID=112176941). Please drill through `Descendants` and `build.log` -- https://bugs.ruby-lang.org/

6 13

[ruby-core:117483] [Ruby master Bug#20419] [BUG] inconsistent freelist length with cppflags='-DRGENGC_CHECK_MODE -DUSE_RUBY_DEBUG_LOG=1'
by znz (Kazuhiro NISHIYAMA) 16 Aug '26

16 Aug '26

Issue #20419 has been reported by znz (Kazuhiro NISHIYAMA). ---------------------------------------- Bug #20419: [BUG] inconsistent freelist length with cppflags='-DRGENGC_CHECK_MODE -DUSE_RUBY_DEBUG_LOG=1' https://bugs.ruby-lang.org/issues/20419 * Author: znz (Kazuhiro NISHIYAMA) * Status: Open * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- `TestGc#test_gc_stress_at_startup` failed on my environment, so I check which configure flags affect. How to reproduce: ``` ./configure cppflags='-DRGENGC_CHECK_MODE -DUSE_RUBY_DEBUG_LOG=1' make miniruby env RUBY_DEBUG=gc_stress ./miniruby -v ``` I can't reproduce with `cppflags='-DRGENGC_CHECK_MODE'` or `cppflags='-DUSE_RUBY_DEBUG_LOG=1'`. ---Files-------------------------------- output.txt (9.44 KB) -- https://bugs.ruby-lang.org/

2 1

[ruby-core:116226] [Ruby master Bug#20189] `rb_str_resize` does not clear coderange when expanding
by tompng (tomoya ishida) 16 Aug '26

16 Aug '26

Issue #20189 has been reported by tompng (tomoya ishida). ---------------------------------------- Bug #20189: `rb_str_resize` does not clear coderange when expanding https://bugs.ruby-lang.org/issues/20189 * Author: tompng (tomoya ishida) * Status: Open * Priority: Normal * ruby -v: ruby 3.4.0dev (2024-01-09T07:07:19Z master db476cc71c) [x86_64-linux] * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- Expanding string in some encoding (utf16 utf32) can change coderange to either valid or broken, but rb_str_resize does not clear coderange. This will cause a bug in c-extension libraries that use rb_str_resize. ~~~ruby # Example for stringio s = StringIO.new("\0".encode('UTF-16LE')) s.truncate(1); s.truncate(2); s.string.valid_encoding? #=> true s.truncate(1); s.string.valid_encoding?; s.truncate(2); s.string.valid_encoding? #=> false (expect to be true) ~~~ -- https://bugs.ruby-lang.org/

5 6

[ruby-core:114943] [Ruby master Bug#19910] Set#delete_if behavior inconsistent with Array/Hash
by segiddins (Samuel Giddins) 16 Aug '26

16 Aug '26

Issue #19910 has been reported by segiddins (Samuel Giddins). ---------------------------------------- Bug #19910: Set#delete_if behavior inconsistent with Array/Hash https://bugs.ruby-lang.org/issues/19910 * Author: segiddins (Samuel Giddins) * Status: Open * Priority: Normal * ruby -v: 3.2.2 * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- Given the following script: ```ruby #!/usr/bin/env ruby require 'set' def enum(collection) i = 0 collection.delete_if do i += 1 raise ArgumentError if i == 6 i.odd? end rescue ArgumentError return collection end pp enum([0, 1, 2, 3, 4, 5, 6, 7]) pp enum([0, 1, 2, 3, 4, 5, 6, 7].to_h { [_1, _1] }) pp enum([0, 1, 2, 3, 4, 5, 6, 7].to_set) ``` It results in: ``` [1, 3, 5, 6, 7] {1=>1, 3=>3, 5=>5, 6=>6, 7=>7} #<Set: {0, 1, 2, 3, 4, 5, 6, 7}> ``` As you can see, when an exception is raise inside `delete_if` on Hash/Array, the already-considered elements are still removed from the array. For `Set`, no elements are deleted (due to the implementation that builds up an intermediary list of elements to delete, then removes them from the underlying hash afterwards). It would be very helpful if `Set#delete_if` behaved consistently with other core collection types -- https://bugs.ruby-lang.org/

5 4

[ruby-core:125003] [Ruby Feature#21953] Allow accessing unshareable objects within a Ractor-local Ruby Box
by tikkss (Tsutomu Katsube) 15 Aug '26

15 Aug '26

Issue #21953 has been reported by tikkss (Tsutomu Katsube). ---------------------------------------- Feature #21953: Allow accessing unshareable objects within a Ractor-local Ruby Box https://bugs.ruby-lang.org/issues/21953 * Author: tikkss (Tsutomu Katsube) * Status: Open ---------------------------------------- ### Status Currently, non-main ractors prohibit access to the following objects to prevent data races: * Global variables * Class variables * Unshareable class instance variables * Unshareable constants ### Proposal I would like to propose that allow reading/writing unshareable objects inside a Ruby Box created in a non-main ractor: ```ruby # lib/x.rb class X # can write unshareable objects XXX = "1" @@cvar = "1" @ivar = "1" class << self def cvar; @@cvar; end def ivar; @ivar; end end end # can read unshareable objects $LOAD_PATH # => returns $LOAD_PATH includes lib directory X.cvar # => "1" X.ivar # => "1" X::XXX # => "1" # main.rb Ractor.new do local_box = Ruby::Box.new local_box.eval <<~RUBY base_dir = File.expand_path(File.dirname(__FILE__)) lib_dir = File.join(base_dir, "lib") # can write unshareable objects $LOAD_PATH.unshift(lib_dir) RUBY local_box.require("x") x = local_box::X.new end.join ``` Ruby Box can isolate global/class variables, class/module definitions from other boxes. A Ruby Box created inside a non-main ractor cannot be accessed from other ractor. If that is the case, wouldn’t it be fine to access unshareable objects inside that box? So I would like to propose that allow reading/writing unshareable objects inside a Ruby Box created in a non-main ractor. ### Background We are working on implementing a Ractor based parallel test runner for the test-unit gem. Ractor is a great for parallel processing. However, many existing libraries still rely on class variables or class instance variables for configuration. Ideally, we should reduce the use of class variables or class instance variables. Currently, we tried fixing several non-shareable objects, but we could not resolve all of them yet. We will continue working on this issue, but we are also exploring other approaches. This is the idea begind this proposal. I think the work needed to make objects shareable when running exisiting libraries with Ractor can be reduced. ### FAQ Q: Can we create a Ruby Box inside a non-main ractor? A: Yes: ```ruby Ractor.new {Ruby::Box.new}.join ``` Q: Is a Ruby Box created in a non-main ractor truly inaccessible from other ractor? A: No. I'm not sure if it's intentional, but a Ruby Box is a shareable object. Also, it can be accessed from the main Ractor by using `Ractor#value`: ```ruby Ractor.shareable?(Ruby::Box.new) # => true ``` ```ruby Ractor.new {Ruby::Box.new}.value # => #<Ruby::Box:3,user,optional> ``` To implement this proposal, Ruby Box may need to be an unshareable object, and passing it with `Ractor#value` may need to be disallowed. -- https://bugs.ruby-lang.org/

5 13

[ruby-core:121829] [Ruby Feature#21308] Replacing the Float#to_s (dtoa.c) implementation with a modern algorithm
by watson1978 (Shizuo Fujita) 12 Aug '26

12 Aug '26

Issue #21308 has been reported by watson1978 (Shizuo Fujita). ---------------------------------------- Feature #21308: Replacing the Float#to_s (dtoa.c) implementation with a modern algorithm https://bugs.ruby-lang.org/issues/21308 * Author: watson1978 (Shizuo Fujita) * Status: Open ---------------------------------------- This is a feature request to replace Ruby's `Float#to_s` implementation with a modern high-performance float-to-string conversion algorithm such as Grisu. Currently, `Float#to_s` in Ruby uses the BSD-derived implementation in [missing/dtoa.c](https://github.com/ruby/ruby/blob/master/missing/dtoa.c). Meanwhile, `json` gem has adopted a Grisu-based implementation in [ruby/json#768](https://github.com/ruby/json/pull/768), it has been improve the performance of float-to-string conversion dramatically. It appears to have brought about a 10 times improvement in performance. However, the improvement is limited to the `json` gem. If we can use the same implementation in `Float#to_s`, it will introduce the improvement in all float-to-string conversion cases. (In additional, it would be better if an API could be added that could be called directly from the C extension library, it will reduce the overhead of the call.) -- https://bugs.ruby-lang.org/

3 3

[ruby-core:121988] [Ruby Bug#21324] Namespace loads RubyGems in root Namespace but it should not
by Eregon (Benoit Daloze) 09 Aug '26

09 Aug '26

Issue #21324 has been reported by Eregon (Benoit Daloze). ---------------------------------------- Bug #21324: Namespace loads RubyGems in root Namespace but it should not https://bugs.ruby-lang.org/issues/21324 * Author: Eregon (Benoit Daloze) * Status: Open * ruby -v: ruby 3.5.0dev (2025-05-10T07:50:29Z namespace-on-read-.. bd4f57f96b) +PRISM [x86_64-linux] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- RubyGems has tons of mutable state, isn't core library and isn't "builtin classes" either, so it should not be in root Namespace, as it is currently: ``` $ RUBY_NAMESPACE=1 ruby -ve 'ns = Namespace.new; p ns::Gem.equal?(Gem)' ruby 3.5.0dev (2025-05-10T07:50:29Z namespace-on-read-.. bd4f57f96b) +PRISM [x86_64-linux] ruby: warning: Namespace is experimental, and the behavior may change in the future! See doc/namespace.md for know issues, etc. true ``` A concrete example of what breaks most likely due to this: ``` $ gem i delegate:0.3.1 $ RUBY_NAMESPACE=1 ruby -ve 'require "delegate"; p Delegator::VERSION; ns = Namespace.new; File.write "ns.rb", "gem %{delegate}, %{0.3.1}; require :delegate.to_s; p Delegator::VERSION"; ns.require "./ns"' ruby 3.5.0dev (2025-05-10T07:50:29Z namespace-on-read-.. bd4f57f96b) +PRISM [x86_64-linux] ruby: warning: Namespace is experimental, and the behavior may change in the future! See doc/namespace.md for know issues, etc. "0.4.0" /home/eregon/prefix/ruby-master/lib/ruby/3.5.0+0/rubygems/specification.rb:2232:in 'Gem::Specification#check_version_conflict': can't activate delegate-0.3.1, already activated delegate-0.4.0 (Gem::LoadError) from /home/eregon/prefix/ruby-master/lib/ruby/3.5.0+0/rubygems/specification.rb:1383:in 'Gem::Specification#activate' from /home/eregon/prefix/ruby-master/lib/ruby/3.5.0+0/rubygems/core_ext/kernel_gem.rb:62:in 'block in Kernel#gem' from /home/eregon/prefix/ruby-master/lib/ruby/3.5.0+0/rubygems/core_ext/kernel_gem.rb:62:in 'Thread::Mutex#synchronize' from /home/eregon/prefix/ruby-master/lib/ruby/3.5.0+0/rubygems/core_ext/kernel_gem.rb:62:in 'Kernel#gem' from /home/eregon/ns.rb:1:in '<top (required)>' from -e:1:in 'Namespace#require' from -e:1:in '<main>' ``` i.e. `ns` sees delegate-0.4.0 was loaded in main namespace but it shouldn't. Previously mentioned in https://bugs.ruby-lang.org/issues/21311#note-36 -- https://bugs.ruby-lang.org/

5 9