Deprecated

• Treating multi-character strings as numbers (you can use a single 32-bit character mapping instead)
• ldio (use ldh instead)
• ld [c] (use ldh instead)
• ldh [$xx] (use ldh [$FFxx] instead)

We now document RGBDS's history of deprecated and removed/replaced features in rgbasm-old.5.

Added

• The contrib/view_palettes.sh script lets you render a GBC .pal file as an image
• RGBASM -s outputs a "state file", listing the values of (non-label) symbols when finished assembling
• RGBASM -Wpurge warns when purging exported symbols or labels
• RGBASM -Wunmatched-directive warns when PUSHC, PUSHO, or PUSHS lacks a POPC, POPO, or POPS
• Symbols can have non-leading $ characters (so an interpolated prefix{numeric} symbol works)
• Symbols can have the same names as reserved keywords by prefixing them with a #
• CHARMAP can map characters to sequences of multiple values, with values not limited to 8 bits
• A string constant . (period) which expands to the current global label scope
• A string constant .. (two periods) which expands to the current fully-qualified local label scope (e.g. Global.local)
• 0x, 0b, and 0o prefixes for hex, binary, and octal numbers (in addition to $, %, and &)
• LOAD FRAGMENT (removed in 0.5.1 due to bugs; we're not totally certain that all bugs are fixed, testing is appreciated!)
• BITWIDTH(n) returns the number of bits necessary to represent n
• TZCOUNT(n) returns the count of trailing zero bits of n
• EXPORT DEF defines and exports a numeric symbol in a single line
• PUSHC name acts like PUSHC followed by SETCHARMAP name
• PUSHS ... acts like PUSHS followed by SECTION ...
• PUSHO ... acts like PUSHO followed by OPT ...
• ENDL is explicitly optional, but with an opt-in -Wunterminated-load warning about it
• cpl can also be written as cpl a
• Allow a no- prefix to negate "meta" warnings (-Wno-all, -Wno-extra, -Wno-everything)
• Allow -Wno-error=... to override -Werror (including for "meta" warnings)
• RGBLINK supports e.g. ROMX FLOATING in linker scripts, which allows assigning a section to no particular bank (this is generally only useful with SDCC object files)
• RGBLINK's .sym file now includes exported numeric constants (if this breaks your tools, please check the .sym specification!)
• RGBGFX -i/--input-tileset uses a given tileset instead of generating all the tiles itself
• RGBGFX -r 0 infers a valid width for the reversed image
• RGBGFX -X or -Y only mirror tiles horizontally or vertically (-X -Y acts like -m)

Changed

• Macro invocations can be at column 1, the very start of a line
• ** exponent operator is right-associative (so p ** q ** r == p ** (q ** r))
• LOW(Label) can be constant if Label is aligned to 8 or more bits
• !expr can be constant 0 if expr has any non-zero bits
• Error messages for undefined symbols mention if the symbol was previously purged
• Sections that grew too big are reported after the whole assembly file has been processed
• When RGBLINK encounters an unknown symbol, it lists the potential un-exported symbols by that name
• RGBLINK reports source locations for conflicts between object files
• Escape characters in section names in map files, and format empty sections more consistently too
• RGBGFX -r gives a detailed warning if -c and -p mismatch; improved several other error messages too
• LOW() and HIGH() have their own RPN operators in the object file (this should lead to nicer output from rgbobj)
• Clarified a lot of documentation, including for fixed-point numbers, macros, and DAA
• Explicitly document that FMOD behaves differently than %
• Increment object file revision number to 11
• Tests can be run with CTest if you use CMake

Fixed

• Label & CONSTANT was not actually doing the & operation!
• Some nonsensical uses of empty local labels (Global.) were ignored
• Many bugs prevented SDCC object files from being processed correctly (special thanks to @RubenZwietering for helping with bugfixing and testing!)
• Crash when assembling a nonexistent file
• Crash when INCLUDEing an unbounded-size file (e.g. /dev/urandom)
• Crash when passing an object file with invalid patch offsets to RGBLINK
• Crash when specifying palette files within RGBGFX at-files
• Crash when reversing an image if the tilemap referred to nonexistent tiles
• Multiple bugs with parsing text palette files (GPL, HEX, and PSP)
• Reversing a 1bpp image had incorrect tile data
• Palette generation was suboptimal, potentially failing to fit within 8 palettes
• Palette generation was also inconsistent between platforms
• Tiles with too many colors were being detected incorrectly
• Maximum number of palettes wrapped around after 255
• Allow text palette files to have the maximum number of colors
• Allow tab character after backslash for line continuation
• Syntax errors at the beginning of a line do not abort assembly
• -Wall did not enable -Wcharmap-redef
• -Wnested-comment was undocumented
• Building works on BSD systems
• Building works on systems with bison 3.8.0

Thanks to @Rangi42 and @ISSOtm , @JL2210 , @avivace , @sukus21 for the work done for this release.