Enable cross-compiling of HogMaker

Author: tophyr

CMakeLists.txt

@@ -15,6 +15,7 @@ option(FORCE_PORTABLE_INSTALL "Install all files into local directory defined by
 option(ENABLE_LOGGER "Enable logging to the terminal" OFF)
 option(ENABLE_MEM_RTL "Enable Real-time library memory management functions (disable to verbose memory allocations)" ON)
 option(BUILD_TESTING "Enable testing. Requires GTest." OFF)
+option(HOST_TOOLS_ONLY "Build only the tools a build host needs, for cross-compilation to a non-native target." OFF)
 
 if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
   option(BUILD_EDITOR "Build internal editor" OFF)
@@ -95,10 +96,11 @@ if(UNIX)
   add_compile_options("$<$<COMPILE_LANGUAGE:C>:${BITS}>")
 endif()
 
-find_package(SDL2 REQUIRED)
-# Some versions of the SDL2 find_package set SDL2_INCLUDE_DIR and some set a plural SDL2_INCLUDE_DIRS. Check both.
-message("SDL2 Include Dir is ${SDL2_INCLUDE_DIR} ${SDL2_INCLUDE_DIRS}")
-
+if(NOT HOST_TOOLS_ONLY)
+  find_package(SDL2 REQUIRED)
+  # Some versions of the SDL2 find_package set SDL2_INCLUDE_DIR and some set a plural SDL2_INCLUDE_DIRS. Check both.
+  message("SDL2 Include Dir is ${SDL2_INCLUDE_DIR} ${SDL2_INCLUDE_DIRS}")
+endif()
 
 if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
   message("Building for Linux")
@@ -169,55 +171,57 @@ include_directories(
   ${PLATFORM_INCLUDES}
 )
 
-add_subdirectory(third_party)
+add_subdirectory(tools)
+if(NOT HOST_TOOLS_ONLY)
+  add_subdirectory(third_party)
+
+  add_subdirectory(2dlib)
+  add_subdirectory(AudioEncode)
+  add_subdirectory(bitmap)
+  add_subdirectory(cfile)
+  add_subdirectory(czip)
+  add_subdirectory(d3music)
+  add_subdirectory(ddebug)
+
+  if(BUILD_EDITOR AND CMAKE_SYSTEM_NAME STREQUAL "Windows")
+    add_subdirectory(dd_grwin32)
+    add_subdirectory(win32)
+  endif()
 
-add_subdirectory(2dlib)
-add_subdirectory(AudioEncode)
-add_subdirectory(bitmap)
-add_subdirectory(cfile)
-add_subdirectory(czip)
-add_subdirectory(d3music)
-add_subdirectory(ddebug)
+  add_subdirectory(linux)
+
+  add_subdirectory(ddio)
+  add_subdirectory(dd_video)
+  add_subdirectory(fix)
+  add_subdirectory(manage)
+  add_subdirectory(grtext)
+  add_subdirectory(mem)
+  add_subdirectory(misc)
+  add_subdirectory(model)
+  add_subdirectory(module)
+  add_subdirectory(movie)
+  add_subdirectory(music)
+  add_subdirectory(networking)
+  add_subdirectory(physics)
+  add_subdirectory(renderer)
+  add_subdirectory(rtperformance)
+  add_subdirectory(sndlib)
+  add_subdirectory(stream_audio)
+  add_subdirectory(ui)
+  add_subdirectory(unzip)
+  add_subdirectory(vecmat)
+  add_subdirectory(libmve)
+  add_subdirectory(md5)
+  add_subdirectory(libacm)
+
+
+  if(BUILD_EDITOR AND CMAKE_SYSTEM_NAME STREQUAL "Windows")
+    add_subdirectory(editor)
+  endif()
 
-if(BUILD_EDITOR AND CMAKE_SYSTEM_NAME STREQUAL "Windows")
-  add_subdirectory(dd_grwin32)
-  add_subdirectory(win32)
-endif()
+  add_subdirectory(Descent3)
 
-add_subdirectory(linux)
-
-add_subdirectory(ddio)
-add_subdirectory(dd_video)
-add_subdirectory(fix)
-add_subdirectory(manage)
-add_subdirectory(grtext)
-add_subdirectory(mem)
-add_subdirectory(misc)
-add_subdirectory(model)
-add_subdirectory(module)
-add_subdirectory(movie)
-add_subdirectory(music)
-add_subdirectory(networking)
-add_subdirectory(physics)
-add_subdirectory(renderer)
-add_subdirectory(rtperformance)
-add_subdirectory(sndlib)
-add_subdirectory(stream_audio)
-add_subdirectory(ui)
-add_subdirectory(unzip)
-add_subdirectory(vecmat)
-add_subdirectory(libmve)
-add_subdirectory(md5)
-add_subdirectory(libacm)
-
-
-if(BUILD_EDITOR AND CMAKE_SYSTEM_NAME STREQUAL "Windows")
-  add_subdirectory(editor)
+  add_subdirectory(netcon)
+  add_subdirectory(netgames)
+  add_subdirectory(scripts)
 endif()
-
-add_subdirectory(Descent3)
-
-add_subdirectory(tools)
-add_subdirectory(netcon)
-add_subdirectory(netgames)
-add_subdirectory(scripts)

README.md

@@ -170,5 +170,19 @@ cmake --build --preset linux --config [Debug|Release]
 
 Once CMake finishes, the built files will be put in `builds/linux/Descent3/Debug` or `builds/linux/Descent3/Release`.
 
+#### Note - Cross-Compiling
+A tool called `HogMaker` is built from source and then used during the Descent3 build in order to create HOG files containing level data. As a result, `HogMaker` must be built as an executable for the architecture _performing_ the build - not the architecture for which you're building. CMake does not support more than one build toolchain in a single build invocation, so if are cross-compiling Descent3 then you will need to configure and build HogMaker individually first:
+```sh
+# configure a "host" build into its own directory, and set HOST_TOOLS_ONLY to 1
+cmake -B builds/host -DHOST_TOOLS_ONLY=1
+# perform the host build
+cmake --build builds/host
+
+# now, configure your real target build, pointing to the existing host tools build
+cmake -B builds/target -DCMAKE_TOOLCHAIN_FILE=/path/to/your/toolchain.cmake -DHogMaker_DIR=$(pwd)/builds/host
+# perform your real build. CMake will not build HogMaker in this invocation, and instead use the previously-built one
+cmake --build builds/target
+```
+
 ## Contributing
 Anyone can contribute! We have an active Discord presence at [Descent Developer Network](https://discord.gg/GNy5CUQ). If you are interested in maintaining the project on a regular basis, please contact Kevin Bentley.

netcon/lanclient/CMakeLists.txt

@@ -11,6 +11,10 @@ target_link_libraries(Direct_TCP_IP PRIVATE
   $<$<PLATFORM_ID:Windows>:ws2_32>
 )
 
+if (HogMaker_DIR)
+  find_package(HogMaker REQUIRED)
+endif()
+
 add_custom_target(Direct_TCP_IP_Hog
   COMMAND $<TARGET_FILE:HogMaker>
   "$<TARGET_FILE_DIR:Descent3>/online/Direct TCP~IP.d3c"

netcon/mtclient/CMakeLists.txt

@@ -17,6 +17,10 @@ target_link_libraries(Parallax_Online PRIVATE
   $<$<PLATFORM_ID:Windows>:ws2_32>
 )
 
+if (HogMaker_DIR)
+  find_package(HogMaker REQUIRED)
+endif()
+
 add_custom_target(Parallax_Online_Hog
   COMMAND $<TARGET_FILE:HogMaker>
   "$<TARGET_FILE_DIR:Descent3>/online/Parallax Online.d3c"

scripts/CMakeLists.txt

@@ -89,6 +89,10 @@ elseif(CMAKE_SYSTEM_NAME STREQUAL "Windows")
   set(HOG_NAME "win")
 endif()
 
+if (HogMaker_DIR)
+  find_package(HogMaker REQUIRED)
+endif()
+
 add_custom_target(HogFull
   COMMAND $<TARGET_FILE:HogMaker>
     "$<TARGET_FILE_DIR:Descent3>/d3-${HOG_NAME}.hog"

tools/CMakeLists.txt

@@ -1,7 +1,12 @@
-add_executable(
-	HogMaker
-	HogMaker/HogFormat.cpp
-	HogMaker/HogMaker.cpp
-)
-add_dependencies(HogMaker get_git_hash)
-target_include_directories(HogMaker PRIVATE ${PROJECT_BINARY_DIR}/lib)
+if (HogMaker_DIR)
+	find_package(HogMaker REQUIRED)
+else()
+	add_executable(
+		HogMaker
+		HogMaker/HogFormat.cpp
+		HogMaker/HogMaker.cpp
+	)
+	export(TARGETS HogMaker FILE "${CMAKE_BINARY_DIR}/HogMakerConfig.cmake")
+	add_dependencies(HogMaker get_git_hash)
+	target_include_directories(HogMaker PRIVATE ${PROJECT_BINARY_DIR}/lib)
+endif()