Protobuf

Ruby
* Fixed quadratic memory use in array append (8379)

PHP
* Fixed quadratic memory use in array append (8379)

C++
* Do not disable RTTI by default in the CMake build (8377)

Ruby
* Fixed SEGV when users pass nil messages (8363)
* Fixed quadratic memory usage when appending to arrays (8364)

C++
* Create a CMake option to control whether or not RTTI is enabled (8361)

PHP
* read_property() handler is not supposed to return NULL (8362)

Ruby
* Ruby <2.7 now uses WeakMap too, which prevents memory leaks. (8341)

Ruby
* Fix for FieldDescriptor.get(msg) (8330)

C++
* Fix PROTOBUF_CONSTINIT macro redefinition (8323)

Ruby
* Bugfix for Message.[] for repeated or map fields (8313)
* Fix for truncating behavior when converting Float to Duration (8320)

C++
* Small fixes for MinGW and for C++20 with GCC (8318)

Protocol Compiler
* Optional fields for proto3 are enabled by default, and no longer require
the --experimental_allow_proto3_optional flag.

C++
* MessageDifferencer: fixed bug when using custom ignore with multiple
unknown fields
* Use init_seg in MSVC to push initialization to an earlier phase.
* Runtime no longer triggers -Wsign-compare warnings.
* Fixed -Wtautological-constant-out-of-range-compare warning.
* DynamicCastToGenerated works for nullptr input for even if RTTI is disabled
* Arena is refactored and optimized.
* Clarified/specified that the exact value of Arena::SpaceAllocated() is an
implementation detail users must not rely on. It should not be used in
unit tests.
* Change the signature of Any::PackFrom() to return false on error.
* Add fast reflection getter API for strings.
* Constant initialize the global message instances
* Avoid potential for missed wakeup in UnknownFieldSet
* Now Proto3 Oneof fields have "has" methods for checking their presence in
C++.
* Bugfix for NVCC
* Return early in _InternalSerialize for empty maps.
* Adding functionality for outputting map key values in proto path logging
output (does not affect comparison logic) and stop printing 'value' in the
path. The modified print functionality is in the
MessageDifferencer::StreamReporter.
* Fixed https://github.com/protocolbuffers/protobuf/issues/8129
* Ensure that null char symbol, package and file names do not result in a
crash.
* Constant initialize the global message instances
* Pretty print 'max' instead of numeric values in reserved ranges.
* Removed remaining instances of std::is_pod, which is deprecated in C++20.
* Changes to reduce code size for unknown field handling by making uncommon
cases out of line.
* Fix std::is_pod deprecated in C++20 (7180)
* Fix some -Wunused-parameter warnings (8053)
* Fix detecting file as directory on zOS issue 8051 (8052)
* Don't include sys/param.h for _BYTE_ORDER (8106)
* remove CMAKE_THREAD_LIBS_INIT from pkgconfig CFLAGS (8154)
* Fix TextFormatMapTest.DynamicMessage issue5136 (8159)
* Fix for compiler warning issue8145 (8160)
* fix: support deprecated enums for GCC < 6 (8164)
* Fix some warning when compiling with Visual Studio 2019 on x64 target (8125)

Python
* Provided an override for the reverse() method that will reverse the internal
collection directly instead of using the other methods of the BaseContainer.
* MessageFactory.CreateProtoype can be overridden to customize class creation.
* Fix PyUnknownFields memory leak (7928)
* Add macOS big sur compatibility (8126)

JavaScript
* Generate `getDescriptor` methods with `*` as their `this` type.
* Enforce `let/const` for generated messages.
* js/binary/utils.js: Fix jspb.utils.joinUnsignedDecimalString to work with negative bitsLow and low but non-zero bitsHigh parameter. (8170)

PHP
* Added support for PHP 8. (8105)
* unregister INI entries and fix invalid read on shutdown (8042)
* Fix PhpDoc comments for message accessors to include "|null". (8136)
* fix: convert native PHP floats to single precision (8187)
* Fixed PHP to support field numbers >=2**28. (8235)
* feat: add support for deprecated fields to PHP compiler (8223)
* Protect against stack overflow if the user derives from Message. (8248)
* Fixed clone for Message, RepeatedField, and MapField. (8245)
* Updated upb to allow nonzero offset minutes in JSON timestamps. (8258)

Ruby
* Added support for Ruby 3. (8184)
* Rewrote the data storage layer to be based on upb_msg objects from the
upb library. This should lead to much better parsing performance,
particularly for large messages. (8184).
* Fill out JRuby support (7923)
* [Ruby] Fix: (SIGSEGV) gRPC-Ruby issue on Windows. memory alloc infinite
recursion/run out of memory (8195)
* Fix jruby support to handle messages nested more than 1 level deep (8194)

Java
* Avoid possible UnsupportedOperationException when using CodedInputSteam
with a direct ByteBuffer.
* Make Durations.comparator() and Timestamps.comparator() Serializable.
* Add more detailed error information for dynamic message field type
validation failure
* Removed declarations of functions declared in java_names.h from
java_helpers.h.
* Now Proto3 Oneof fields have "has" methods for checking their presence in
Java.
* Annotates Java proto generated *_FIELD_NUMBER constants.
* Add -assumevalues to remove JvmMemoryAccessor on Android.

C
* Fix parsing negative Int32Value that crosses segment boundary (8035)
* Change ByteString to use memory and support unsafe create without copy (7645)
* Optimize MapField serialization by removing MessageAdapter (8143)
* Allow FileDescriptors to be parsed with extension registries (8220)
* Optimize writing small strings (8149)