Protobuf

C++
* cmake: Call get_filename_component() with DIRECTORY mode instead of PATH mode (9614)
* Escape GetObject macro inside protoc-generated code (9739)
* Update CMake configuration to add a dependency on Abseil (9793)
* Fix cmake install targets (9822)
* Use __constinit only in GCC 12.2 and up (9936)

Java
* Update protobuf_version.bzl to separate protoc and per-language java … (9900)

Python
* Increment python major version to 4 in version.json for python upb (9926)
* The C extension module for Python has been rewritten to use the upb library.
This is expected to deliver significant performance benefits, especially when
parsing large payloads. There are some minor breaking changes, but these
should not impact most users. For more information see:
https://developers.google.com/protocol-buffers/docs/news/2022-05-06#python-updates
* Fixed win32 build and fixed str(message) on all Windows platforms. (9976)
* The binary wheel for macOS now supports Apple silicon.

PHP
* [PHP] fix PHP build system (9571)
* Fix building packaged PHP extension (9727)
* fix: reserve "ReadOnly" keyword for PHP 8.1 and add compatibility (9633)
* fix: phpdoc syntax for repeatedfield parameters (9784)
* fix: phpdoc for repeatedfield (9783)
* Change enum string name for reserved words (9780)
* chore: [PHP] fix phpdoc for MapField keys (9536)
* Fixed PHP SEGV by not writing to shared memory for zend_class_entry. (9996)

Ruby
* Allow pre-compiled binaries for ruby 3.1.0 (9566)
* Implement `respond_to?` in RubyMessage (9677)
* [Ruby] Fix RepeatedFieldlast, first inconsistencies (9722)
* Do not use range based UTF-8 validation in truffleruby (9769)
* Improve range handling logic of `RepeatedField` (9799)
* Support x64-mingw-ucrt platform

Other
* [Kotlin] remove redundant public modifiers for compiled code (9642)
* [C] Update GetExtension to support getting typed value (9655)
* Fix invalid dependency manifest when using `descriptor_set_out` (9647)
* Fix C generator handling of a field named "none" in a oneof (9636)
* Add initial version.json file for 21-dev (9840)
* Remove duplicate java generated code (9909)
* Cherry-pick PR 9981 into 21.x branch (10000)

Python
* Fix windows builds
* Throw more helpful error if generated code is out of date
* Fixed two reference leaks

Ruby
* Support x64-mingw-ucrt platform

PHP
* Fix SEGV by not writing to shared memory for zend_class_entry

C
* Suppress warning CS8981

Other
* Fix Maven release to release actual osx_aarch64 binary
* Fix protoc zips to have the proto files for well known types

Versions
* Versioning scheme is changing to decouple major versions for languages
* Minor and patch versions will remain coupled
* Compilers and releases will refer to the version as just the minor and micro versions (i.e. 21.0)
* See [here](https://developers.google.com/protocol-buffers/docs/news/2022-05-06) for more information on this change
C++
* Rename main cmake/CMakeLists.txt to CMakeLists.txt (9603)
* avoid allocating memory if all extension are cleared (9345)
* cmake: Call get_filename_component() with DIRECTORY mode instead of PATH mode (9614)
* Escape GetObject macro inside protoc-generated code (9739)
* Update CMake configuration to add a dependency on Abseil (9793)
* Use __constinit only in GCC 12.2 and up (9936)
* Refactor generated message class layout
* Optimize tokenizer ParseInteger by removing division
* Reserve exactly the right amount of capacity in ExtensionSet::MergeFrom
* Parse FLT_MAX correctly when represented in JSON

Java
* Update protobuf_version.bzl to separate protoc and per-language java … (9900)
* 6x speedup in ArrayEncoder.writeUInt32NotTag

Python
* Increment python major version to 4 in version.json for python upb (9926)
* The C extension module for Python has been rewritten to use the upb library.
This is expected to deliver significant performance benefits, especially when
parsing large payloads. There are some minor breaking changes, but these
should not impact most users. For more information see:
https://developers.google.com/protocol-buffers/docs/news/2022-05-06#python-updates
* Due to the breaking changes for Python, the major version number for Python
has been incremented.
* The binary wheel for macOS now supports Apple silicon.

PHP
* chore: [PHP] fix phpdoc for MapField keys (9536)
* [PHP] Remove unnecessary zval initialization (9600)
* [PHP] fix PHP build system (9571)
* Fix building packaged PHP extension (9727)
* fix: reserve "ReadOnly" keyword for PHP 8.1 and add compatibility (9633)
* fix: phpdoc syntax for repeatedfield parameters (9784)
* fix: phpdoc for repeatedfield (9783)
* Change enum string name for reserved words (9780)
* Fixed composer.json to only advertise compatibility with PHP 7.0+. (9819)

Ruby
* Allow pre-compiled binaries for ruby 3.1.0 (9566)
* Implement `respond_to?` in RubyMessage (9677)
* [Ruby] Fix RepeatedFieldlast, first inconsistencies (9722)
* Do not use range based UTF-8 validation in truffleruby (9769)
* Improve range handling logic of `RepeatedField` (9799)
* Disable the aarch64 build on macOS until it can be fixed. (9816)

Compiler
* Protoc outputs the list of suggested field numbers when invalid field
numbers are specified in the .proto file.
* Require package names to be less than 512 bytes in length

Other
* [Kotlin] remove redundant public modifiers for compiled code (9642)
* [C] Update GetExtension to support getting typed value (9655)
* Fix invalid dependency manifest when using `descriptor_set_out` (9647)
* Fix C generator handling of a field named "none" in a oneof (9636)
* Add initial version.json file for 21-dev (9840)
* Remove duplicate java generated code (9909)
* Fix versioning issues in 3.20.0

Java
* Refactoring java full runtime to reuse sub-message builders and prepare to
migrate parsing logic from parse constructor to builder.
* Move proto wireformat parsing functionality from the private "parsing
constructor" to the Builder class.
* Change the Lite runtime to prefer merging from the wireformat into mutable
messages rather than building up a new immutable object before merging. This
way results in fewer allocations and copy operations.
* Make message-type extensions merge from wire-format instead of building up
instances and merging afterwards. This has much better performance.
* Fix TextFormat parser to build up recurring (but supposedly not repeated)
sub-messages directly from text rather than building a new sub-message and
merging the fully formed message into the existing field.
* This release addresses a [Security Advisory for Java users](https://github.com/protocolbuffers/protobuf/security/advisories/GHSA-h4h5-3hr4-j3g2)

C++
* Reduce memory consumption of MessageSet parsing
* This release addresses a [Security Advisory for C++ and Python users](https://github.com/protocolbuffers/protobuf/security/advisories/GHSA-8gq9-2x98-w8hf)

PHP
* Fix building packaged PHP extension (9727)
* Fixed composer.json to only advertise compatibility with PHP 7.0+. (9819)

Ruby
* Disable the aarch64 build on macOS until it can be fixed. (9816)

Other
* Fix versioning issues in 3.20.0