Feature #22274: Make `IO::Buffer` no longer experimental.

• Status: Open
• Assignee: ioquatix (Samuel Williams)
• Target version: -

[ioquatix (Samuel Williams)]

IO::Buffer was introduced in Ruby 3.1 by Feature #18020 as an experimental API. It provides an efficient buffer abstraction for fiber scheduler I/O, zero-copy operations, binary protocol implementations, and access from native extensions.

Since then, the API has seen several Ruby releases of real-world use and substantial development. Ruby 4.1 now has cohesive semantics for buffer ownership and lifecycle, slicing, locking, string and file mappings, MemoryView integration, and single-transfer I/O operations.

I propose making both the Ruby and public C interfaces of IO::Buffer non-experimental in Ruby 4.1.

This would involve:

• Removing the allocation-time experimental warning.
• Removing the experimental status from the class documentation.
• Removing RB_IO_BUFFER_EXPERIMENTAL from the public C header.
• Removing warning suppression that is only required because IO::Buffer is experimental.
• Updating NEWS to describe IO::Buffer as stable.

RUBY_IO_BUFFER_VERSION would remain available for compile-time feature detection as the interface continues to evolve.

Before stabilizing the interface, I would particularly appreciate feedback from JRuby and TruffleRuby maintainers.

Related work:

• Original proposal: https://bugs.ruby-lang.org/issues/18020
• CRuby implementation PR: https://github.com/ruby/ruby/pull/18486
• TruffleRuby implementation: https://github.com/truffleruby/truffleruby/pull/4248
• JRuby implementation: https://github.com/jruby/jruby/blob/master/core/src/main/java/org/jruby/RubyIOBuffer.java
• JRuby file-mapping issue: https://github.com/jruby/jruby/issues/8714