Add Dreamcast platform support

3rdParty/Lua/CMakeLists.txt

@@ -30,7 +30,7 @@ elseif(TARGET_PLATFORM STREQUAL "dos")
   target_compile_definitions(lua_static PUBLIC -DLUA_USE_C89)
 elseif(ANDROID AND ("${ANDROID_ABI}" STREQUAL "armeabi-v7a" OR "${ANDROID_ABI}" STREQUAL "x86"))
   target_compile_definitions(lua_static PUBLIC -DLUA_USE_C89)
-elseif(NINTENDO_3DS OR VITA OR NINTENDO_SWITCH OR NXDK)
+elseif(NINTENDO_3DS OR VITA OR NINTENDO_SWITCH OR NXDK OR DREAMCAST)
   target_compile_definitions(lua_static PUBLIC -DLUA_USE_C89)
 elseif(IOS)
   target_compile_definitions(lua_static PUBLIC -DLUA_USE_IOS)

3rdParty/libfmt/CMakeLists.txt

@@ -15,10 +15,23 @@ else()
   set(BUILD_SHARED_LIBS ON)
 endif()
 include(FetchContent)
-FetchContent_Declare_ExcludeFromAll(libfmt
-  URL https://github.com/fmtlib/fmt/releases/download/12.0.0/fmt-12.0.0.zip
-  URL_HASH SHA256=1c32293203449792bf8e94c7f6699c643887e826f2d66a80869b4f279fb07d25
-)
+if(DREAMCAST)
+  set(DREAMCAST_FMT_PATCH "${CMAKE_CURRENT_LIST_DIR}/fmt-12.0.0-sh4-long-double.patch")
+  if(NOT EXISTS "${DREAMCAST_FMT_PATCH}")
+    message(FATAL_ERROR "Dreamcast fmt patch not found: ${DREAMCAST_FMT_PATCH}")
+  endif()
+  find_program(DREAMCAST_PATCH_EXECUTABLE patch REQUIRED)
+  FetchContent_Declare_ExcludeFromAll(libfmt
+    URL https://github.com/fmtlib/fmt/releases/download/12.0.0/fmt-12.0.0.zip
+    URL_HASH SHA256=1c32293203449792bf8e94c7f6699c643887e826f2d66a80869b4f279fb07d25
+    PATCH_COMMAND "${DREAMCAST_PATCH_EXECUTABLE}" -p1 -N -i "${DREAMCAST_FMT_PATCH}"
+  )
+else()
+  FetchContent_Declare_ExcludeFromAll(libfmt
+    URL https://github.com/fmtlib/fmt/releases/download/12.0.0/fmt-12.0.0.zip
+    URL_HASH SHA256=1c32293203449792bf8e94c7f6699c643887e826f2d66a80869b4f279fb07d25
+  )
+endif()
 FetchContent_MakeAvailable_ExcludeFromAll(libfmt)
 
 # We do not use locale-specific features of libfmt and disabling them reduces the size.

3rdParty/libfmt/fmt-12.0.0-sh4-long-double.patch

@@ -0,0 +1,31 @@
+From: KOS Dreamcast Port
+Subject: Fix libfmt 12.0.0 long double support on SH4
+
+On SH4 with -m4-single, long double is IEEE 754 binary64 (same as double)
+but std::numeric_limits<long double>::digits == 53, which doesn't match
+fmt's expected values of 64 or 113 for extended precision types.
+
+This causes the float_info<long double> template to be incomplete,
+resulting in compilation errors:
+  error: invalid use of incomplete type 'struct float_info<long double>'
+
+This patch adds an explicit specialization for long double when it has
+binary64 characteristics (53 mantissa bits, 8 bytes).
+
+--- a/include/fmt/format.h
++++ b/include/fmt/format.h
+@@ -1462,6 +1462,14 @@ template <> struct float_info<double> {
+   static const int shorter_interval_tie_lower_threshold = -77;
+   static const int shorter_interval_tie_upper_threshold = -77;
+ };
++
++// SH4/Dreamcast fix: long double is IEEE 754 binary64 on this platform.
++// Provide explicit specialization when long double has 53 mantissa bits.
++#if defined(__LDBL_MANT_DIG__) && (__LDBL_MANT_DIG__ == 53) && \
++    defined(__SIZEOF_LONG_DOUBLE__) && (__SIZEOF_LONG_DOUBLE__ == 8)
++template <>
++struct float_info<long double> : float_info<double> {};
++#endif
+
+ // An 80- or 128-bit floating point number.
+ template <typename T>

CMake/Platforms.cmake

@@ -51,6 +51,10 @@ if(NINTENDO_3DS)
   include(platforms/n3ds)
 endif()
 
+if(DREAMCAST)
+  include(platforms/dreamcast)
+endif()
+
 if(VITA)
   include("$ENV{VITASDK}/share/vita.cmake" REQUIRED)
   include(platforms/vita)

CMake/functions/devilutionx_library.cmake

@@ -46,8 +46,9 @@ function(add_devilutionx_library NAME)
     target_compile_options(${NAME} PUBLIC -Wall -Wextra -Wno-unused-parameter)
   endif()
 
-  if(NOT WIN32 AND NOT APPLE AND NOT ${CMAKE_SYSTEM_NAME} STREQUAL FreeBSD)
+  if(NOT WIN32 AND NOT APPLE AND NOT ${CMAKE_SYSTEM_NAME} STREQUAL FreeBSD AND NOT DREAMCAST)
     # Enable POSIX extensions such as `readlink` and `ftruncate`.
+    # Excluded for Dreamcast/KOS which doesn't have full POSIX support.
     add_definitions(-D_POSIX_C_SOURCE=200809L)
   endif()
 

CMake/platforms/dreamcast.cmake

@@ -0,0 +1,79 @@
+# Not automatically defined by sh-elf-gcc
+add_compile_definitions(__DREAMCAST__)
+
+set(CMAKE_BUILD_TYPE MinSizeRel CACHE STRING "" FORCE)
+
+set(ASAN OFF)
+set(UBSAN OFF)
+set(BUILD_TESTING OFF)
+set(NONET ON)
+set(USE_SDL1 ON)
+set(NOEXIT ON)
+set(PREFILL_PLAYER_NAME ON)
+set(DISABLE_DEMOMODE ON)
+set(DEVILUTIONX_SYSTEM_LIBSODIUM OFF)
+set(DEVILUTIONX_SYSTEM_SDL_IMAGE OFF)
+set(UNPACKED_MPQS OFF)
+
+# CD reads via MPQ are too slow for real-time audio
+set(DISABLE_STREAMING_SOUNDS ON)
+set(DEFAULT_AUDIO_BUFFER_SIZE 2048)
+set(DEFAULT_AUDIO_SAMPLE_RATE 22050)
+set(DEFAULT_AUDIO_RESAMPLING_QUALITY 0)
+
+set(DEFAULT_PER_PIXEL_LIGHTING 0)
+set(DEVILUTIONX_PALETTE_TRANSPARENCY_BLACK_16_LUT ON CACHE BOOL "" FORCE)
+
+# GPF SDL supports 8bpp with hardware palette - lets SDL handle the
+# palette-to-RGB conversion internally via PVR DMA, avoiding the
+# manual 8bpp->16bpp conversion in dc_video.cpp entirely.
+set(SDL1_VIDEO_MODE_BPP 8)
+set(SDL1_VIDEO_MODE_FLAGS SDL_DOUBLEBUF|SDL_HWSURFACE)
+
+set(DEFAULT_WIDTH 640)
+set(DEFAULT_HEIGHT 480)
+
+# VMU saves use flat files with zlib compression
+set(UNPACKED_SAVES ON)
+
+set(DEVILUTIONX_GAMEPAD_TYPE Generic)
+
+# GPF SDL button IDs (from SDL_dreamcast.h SDL_DC_button enum)
+set(JOY_BUTTON_A 2)
+set(JOY_BUTTON_B 1)
+set(JOY_BUTTON_X 5)
+set(JOY_BUTTON_Y 6)
+set(JOY_BUTTON_START 3)
+
+set(JOY_HAT_DPAD_UP_HAT 0)
+set(JOY_HAT_DPAD_DOWN_HAT 0)
+set(JOY_HAT_DPAD_LEFT_HAT 0)
+set(JOY_HAT_DPAD_RIGHT_HAT 0)
+set(JOY_HAT_DPAD_UP 1)
+set(JOY_HAT_DPAD_DOWN 4)
+set(JOY_HAT_DPAD_LEFT 8)
+set(JOY_HAT_DPAD_RIGHT 2)
+
+set(JOY_AXIS_LEFTX 0)
+set(JOY_AXIS_LEFTY 1)
+
+list(APPEND DEVILUTIONX_PLATFORM_SUBDIRECTORIES platform/dreamcast)
+list(APPEND DEVILUTIONX_PLATFORM_LINK_LIBRARIES libdevilutionx_dreamcast)
+
+# FindZLIB may not create this target during cross-compilation.
+if(NOT TARGET ZLIB::ZLIB)
+    add_library(ZLIB::ZLIB STATIC IMPORTED)
+    set_target_properties(ZLIB::ZLIB PROPERTIES
+        IMPORTED_LOCATION "${ZLIB_LIBRARY}"
+        INTERFACE_INCLUDE_DIRECTORIES "${ZLIB_INCLUDE_DIR}"
+    )
+endif()
+
+# FindBZip2 may not create this target during cross-compilation
+if(NOT TARGET BZip2::BZip2)
+    add_library(BZip2::BZip2 STATIC IMPORTED)
+    set_target_properties(BZip2::BZip2 PROPERTIES
+        IMPORTED_LOCATION "${BZIP2_LIBRARIES}"
+        INTERFACE_INCLUDE_DIRECTORIES "${BZIP2_INCLUDE_DIR}"
+    )
+endif()

CMake/platforms/dreamcast.toolchain.cmake

@@ -0,0 +1,67 @@
+# DevilutionX Dreamcast Toolchain
+# We extend the official KOS toolchain to add project-specific settings.
+
+if(NOT DEFINED ENV{KOS_CMAKE_TOOLCHAIN})
+    message(FATAL_ERROR "KOS_CMAKE_TOOLCHAIN not defined. Please source environ.sh.")
+endif()
+
+# 1. Load the official KOS toolchain
+# This sets up compilers, flags (-m4-single), and system paths correctly.
+include("$ENV{KOS_CMAKE_TOOLCHAIN}")
+
+# 2. Set DevilutionX specific platform flag
+# This triggers loading CMake/platforms/dreamcast.cmake
+set(DREAMCAST ON)
+
+# 3. Add our include paths
+# KOS ports often hide headers in subdirectories
+# GPF SDL installs to KOS_BASE/addons/include/dreamcast/SDL/
+list(APPEND CMAKE_INCLUDE_PATH
+    "$ENV{KOS_PORTS}/include/zlib"
+    "$ENV{KOS_PORTS}/include/bzlib"
+    "$ENV{KOS_BASE}/addons/include/dreamcast/SDL"
+)
+
+# 4. Force libraries (The "Nuclear Option" for sub-projects)
+# Standard find modules struggle with KOS layout, so we force them.
+set(ZLIB_INCLUDE_DIR "$ENV{KOS_PORTS}/include/zlib" CACHE PATH "ZLIB Include Dir" FORCE)
+set(ZLIB_LIBRARY "$ENV{KOS_PORTS}/lib/libz.a" CACHE FILEPATH "ZLIB Library" FORCE)
+set(BZIP2_INCLUDE_DIR "$ENV{KOS_PORTS}/include/bzlib" CACHE PATH "BZip2 Include Dir" FORCE)
+set(BZIP2_LIBRARIES "$ENV{KOS_PORTS}/lib/libbz2.a" CACHE FILEPATH "BZip2 Library" FORCE)
+
+# 5. Force SDL1 - GPF SDL (SDL-dreamhal--GLDC) for DMA video and hardware palette
+# GPF SDL installs via its Makefile.dc to KOS_BASE/addons/{lib,include}/dreamcast/
+set(SDL_INCLUDE_DIR "$ENV{KOS_BASE}/addons/include/dreamcast/SDL" CACHE PATH "SDL Include Dir" FORCE)
+set(SDL_LIBRARY "$ENV{KOS_BASE}/addons/lib/dreamcast/libSDL.a" CACHE FILEPATH "SDL Library" FORCE)
+
+# 6. Fix libfmt and magic_enum compilation
+# Disable long double support because sh4-gcc's long double (64-bit) confuses libfmt
+# Disable magic_enum asserts because GCC 15's stricter parsing breaks them in comma expressions
+add_compile_definitions(FMT_USE_LONG_DOUBLE=0 FMT_USE_FLOAT128=0 MAGIC_ENUM_NO_ASSERT)
+
+# 7. KOS doesn't have pthreads as a separate library - threading is built into libkallisti
+set(CMAKE_THREAD_LIBS_INIT "" CACHE STRING "" FORCE)
+set(CMAKE_HAVE_THREADS_LIBRARY 1)
+set(Threads_FOUND TRUE)
+
+# 8. Remove host system library paths that sneak in
+set(CMAKE_EXE_LINKER_FLAGS "" CACHE STRING "" FORCE)
+set(CMAKE_SHARED_LINKER_FLAGS "" CACHE STRING "" FORCE)
+
+# 8b. Ignore host system paths (homebrew, etc.) to prevent finding wrong libraries
+set(CMAKE_IGNORE_PATH "/opt/homebrew;/opt/homebrew/include;/opt/homebrew/lib;/usr/local;/usr/local/include;/usr/local/lib" CACHE STRING "" FORCE)
+
+# 8c. Force using bundled magic_enum (not system/homebrew version)
+set(DEVILUTIONX_SYSTEM_MAGIC_ENUM OFF CACHE BOOL "" FORCE)
+
+# 9. Override Link Rule to use Grouping
+# KOS toolchain already adds -T, -nodefaultlibs, and -L paths via <LINK_FLAGS>
+# We just need to add --start-group/--end-group for circular dependency resolution
+# NOTE: kos_add_romdisk() in CMakeLists.txt handles -lromdiskbase with --whole-archive
+set(CMAKE_CXX_LINK_EXECUTABLE
+    "<CMAKE_CXX_COMPILER> <FLAGS> <LINK_FLAGS> <OBJECTS> -o <TARGET> -Wl,--start-group <LINK_LIBRARIES> -lkallisti -lc -lgcc -lm -lstdc++ -Wl,--end-group")
+set(CMAKE_C_LINK_EXECUTABLE
+    "<CMAKE_C_COMPILER> <FLAGS> <LINK_FLAGS> <OBJECTS> -o <TARGET> -Wl,--start-group <LINK_LIBRARIES> -lkallisti -lc -lgcc -lm -lstdc++ -Wl,--end-group")
+
+# 10. Skip compiler checks (saves time and avoids romdisk symbol issues)
+set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)

Packaging/dreamcast/.gitignore

@@ -0,0 +1,50 @@
+# Build artifacts
+*.iso
+*.cdi
+*.bin
+
+# Disc staging directories
+cd_root/
+flycast_disc/
+romdisk/
+objects/
+towners/
+items/
+levels/
+monsters/
+music/
+nlevels/
+plrgfx/
+sfx/
+speech/
+ui_art/
+data/
+fonts/
+gendata/
+arena/
+
+# Extracted game data (copyrighted)
+diabdat/
+DIABDAT.MPQ
+spawn.mpq
+
+# Extracted file dumps (from MPQ tools)
+File[0-9]*.pcx
+File[0-9]*.wav
+File[0-9]*.xxx
+File[0-9]*.gif
+File[0-9]*.smk
+
+# GPF SDL source (cloned by build.sh)
+SDL-gpf/
+
+# Build tool output
+*.o
+
+# Listfiles (generated)
+*_listfile*.txt
+
+# Python / IDE
+.venv/
+.qodo/
+__pycache__/

Packaging/dreamcast/README.md

@@ -0,0 +1,39 @@
+# Dreamcast Build
+
+This folder contains the Dreamcast packaging flow for DevilutionX.
+
+## Prerequisites
+
+- [KallistiOS](https://kos-docs.dreamcast.wiki/) (KOS) with kos-ports (zlib, bzip2)
+- [`mkdcdisc`](https://gitlab.com/simulant/mkdcdisc) for CDI disc image creation
+
+SDL (GPF SDL with DMA video) and Lua are built from source automatically by `build.sh`.
+No external `fmt` patch is required. The build applies a bundled SH4 `libfmt` patch automatically.
+
+## Game Data (Required)
+
+- You must provide your own MPQ files. Diablo data files are proprietary assets owned by Blizzard.
+- Copy `DIABDAT.MPQ` to `Packaging/dreamcast/cd_root/`.
+- `spawn.mpq` is optional for shareware mode.
+- For extraction methods, see [Extracting MPQs from the GoG installer](https://github.com/diasurgical/devilutionX/wiki/Extracting-MPQs-from-the-GoG-installer).
+
+## Build
+
+From repo root:
+
+```sh
+./Packaging/dreamcast/build.sh
+```
+
+## Output
+
+- Intermediate ELF: `build-dreamcast/devilutionx.elf`
+- Bootable CDI: `Packaging/dreamcast/devilutionx-playable.cdi`
+
+## Notes
+
+- `build.sh` deletes and recreates `build-dreamcast/`.
+- Override tool paths with env vars if needed:
+  - `KOS_BASE`
+  - `KOS_ENV`
+  - `MKDCDISC`