Premake is the tool used to build 0 A.D. from source code. It is a critical part of the "build system". Premake uses Lua scripts to create workspaces both for building Premake itself and other projects like 0 A.D. It mostly supports Visual Studio (Windows), Xcode (OS X) and GNU make (*nix and OS X).
Premake in 0 A.D.
0 A.D. uses two custom Lua scripts to generate its workspaces with Premake:
- build/premake/premake4.lua - this is the main script which controls compiler, linker, and workspace behavior on different platforms.
- build/premake/extern_libs4.lua - this is an auxiliary script, which lists external dependencies / libraries used by 0 A.D. and how they differ on various platforms.
These scripts are well commented, describing the reasoning behind most of the logic.
Generating the workspaces is quite simple and done automatically by the update-workspaces step(s) of our BuildInstructions. The Premake binary is run as with the following command:
premake4/bin/release/premake4 --file="premake4.lua" --outpath="../workspaces/gcc/" gmake
This tells Premake to use our custom premake4.lua to generate a GNU make workspace located in build/workspaces/gcc/. Those options are self-explanatory, but there are a number of other options supported by Premake and our custom scripts, listed below.
Our Premake build supports the following workspaces, but not on every platform (e.g. xcode3 probably won't work on Windows or Linux).
- vs2010 - Visual Studio 2010 (or Express)
- vs2008 - Visual Studio 2008 (or Express)
- vs2005 - Visual Studio 2005 (or Express)
- gmake - GNU Make
- xcode3 - Apple Xcode 3
- xcode4 - Apple Xcode 4
- codeblocks - Code::Blocks
Note: In most cases we've had to modify the default workspaces for bug fixes, so additional platforms might be supported by Premake in theory but broken in practice. Our main goal is to have an acceptable workspace on each of our main supported platforms: Windows w/ MSVC, Linux w/ make, and OS X w/ Xcode. Supporting additional platforms is less of a priority.
In addition to --file and --outpath, our scripts support the following options (also prefixed with "--"):
- android - Use non-working Android cross-compiling mode
- atlas - Include Atlas scenario editor projects
- collada - Include COLLADA projects (requires FCollada library)
- coverage - Enable code coverage data collection (GCC only)
- gles - Use non-working OpenGL ES 2.0 mode
- icc - Use Intel C++ Compiler (Linux only; should use either --cc icc or --without-pch too, and then set CXX=icpc before calling make)
- macosx-bundle - Set the compiled binary as an OS X bundle with the given identifier string, e.g. "com.wildfiregames.0ad".
- macosx-version-min - Set minimum required version of the OS X APIs to use, e.g. "10.6".
- minimal-flags - Only set compiler/linker flags that are really needed. Has no effect on Windows builds. Use this to set your own compiler/linker flags (CXXFLAGS, LDFLAGS)
- with-system-nvtt - Search standard paths for nvidia-texture-tools library, instead of using bundled copy
- with-system-enet - Search standard paths for libenet, instead of using bundled copy
- with-system-mozjs185 - Search standard paths for libmozjs185, instead of using bundled copy
- without-audio - Disable use of OpenAL/Ogg/Vorbis APIs
- without-nvtt - Disable use of NVTT
- without-pch - Disable generation and usage of precompiled headers
- without-tests - Disable generation of test projects
- bindir - Directory for executables (typically /usr/games); default is to be relocatable
- datadir - Directory for data files (typically /usr/share/games/0ad); default is ../data/ relative to executable
- libdir - Directory for libraries (typically /usr/lib/games/0ad); default is ./ relative to executable
- sysroot - Root directory for SDK builds, sets the sysroot compiler flag and syslibroot linker flag (e.g. /usr/lib becomes SYSROOT/usr/lib).
Note: Most of the options are special purpose and not needed for the average build. You shouldn't use an option unless you understand it and have a need for it.
The most commonly used options are --atlas and --collada (you might want to disable them if building the game on an experimental new platform like Android). --atlas is not used by default in update-workspaces.bat, because we don't bundle the wxWidgets libraries in SVN. If you are using update-workspaces.sh Atlas is built by default. Use --disable-atlas to skip it.
The update-workspaces scripts will pass arguments through to Premake:
./update-workspaces.sh --without-tests --with-system-mozjs185
For Windows developers, we bundle a pre-built, 32-bit premake.exe in SVN. This EXE only needs to be updated when the Premake source code is modified, which happens infrequently.
To modify Premake's behavior, you typically modify the Lua scripts within build/premake/premake4. You shouldn't modify its build files or scripts.c directly, as these are automatically generated from the scripts. Obviously you need a working, already built Premake binary to do this. This is slightly confusing in that Premake creates the workspace you need to build a new version of Premake.
After you've modified Premake's source scripts, you need to run the old Premake binary with the embed option to update e.g. src/host/scripts.c, see Building Premake for more information.
Generating Premake's workspaces
Premake's own workspaces and Makefiles are mostly generated using a Premake binary and the contents of build/premake/premake4/premake4.lua - the Premake4 build configuration script (not to be confused with the game's custom premake4.lua script, one directory higher). Building Premake and running it with the --help option will list available options, the basic invocation is as follows (on *nix):
./bin/release/premake4 --os=linux --to=build/gmake.unix/ gmake
This will generate a Linux-compatible Makefile in the build/gmake.unix subdirectory. Using a similar process it should be possible to generate any supported OS- or toolset-specific workspace for Premake. Note: some of the results may need hand-editing to work around Premake bugs, so use with caution. When possible it should be preferred to fix the bugs instead.