17 December 2020. Summary of changes for version 20201217:

This release is available at https://acpica.org/downloads [2]

1) ACPICA kernel-resident subsystem:

Note: The implementation of ACPI 6.4 is underway, and is expected to be mostly finished next month, when ACPI 6.4 is released.

From qzed:- fixed-ae-class-macros. Fix exception code class checks. Added several new macros, such as ACPI_CNTL_EXCEPTION(Status) in order to enable this.

AcpiExec/iASL/AcpiHelp: Added a few changes for support of GCC 10.2.0. These included a few casts, as well as a null pointer check.

Fix -Wfallthrough: GCC 7.1 gained -Wimplicit-fallthrough to warn on implicit fallthrough, as well as __attribute__((__fallthrough__)) and comments to explicitly denote that cases of fallthrough were intentional. Clang also supports this warning and statement attribute, but not the comment form. Added a new macro, ACPI_FALLTHROUGH to support this feature of GCC. With assistance from @nickdesaulniers.

2) iASL Compiler/Disassembler and ACPICA tools:

Added improvement to method call analysis by saving the return type and relaxing certain cases of type checking.

iASL Table Compiler: Improved info messages. Added a message to the -T option for when the default template (DSDT) is used.
Also added a note for when multiple SSDTs are created with a DSDT that the SSDTs are created in the same file as the DSDT.