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convert Lua source code into an equivalent C source code written in terms of Lua C API calls
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davidm/lua2c
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lua2c - converts Lua 5.1 source code to C code. == Description == This utility converts a given Lua source file into an equivalent C source file written in terms of Lua C API calls. At least, this works for a large subset of the Lua language (see limitations below). The compiler is written entirely in Lua, and no build/install is needed. This project reuses Metalua's gg/mlp parser to convert Lua source to a Metalua-style [1] AST over which the compiler then operates. lua2c does not require Metalua itself though since gg/mlp is bundled in the distribution and is written in pure Lua. == Usage == Example usage: lua lua2c.lua test/bisect.lua which generates a C file to standard output. You may also use the shell script "clua" to compile Lua->C->machine code and execute all in one step. However, you may need to edit the variables in the file to match your system since this utility invokes the C compiler. ./clua test/bisect.lua lua2c can even compile itself! (Note: the -c option compiles only without running.) ./clua -c lua2c.lua # compile lua2c binary ./lua2c examples-lua/bisect.lua # test == Related Work == * luac2c - This related effort by Hisham Muhammad [2] converts Lua bytecodes to C source, whereas this project converts Lua source to C source. luac2c runs into a few similar limitations as given below. luac2c has remained experimental but superseded Luiz Henrique De Figueiredo's very basic but similarly named lua2c for Lua 4.0 [3]. * luagen++ [4] uses C++ expression templates to translate Lua-like C++ statements to C API calls. Some of the code generation structure is actually fairly similar to lua2c. * Python Pyrex [5] does something similar in Python but has the added goal of lowering the boundary between C and Python code. Something like that could be done with lua2c, especially since lua2c uses the extensible gg parser. * Clue by David Given [6] does the opposite: convert C source to Lua source. * luac + BinToCee allow compilation of Lua source to bytecodes and/or embedding in a C file. == Potential Uses == I think this project not only is theoretically nice to have but has a number of potential uses: * Provide another approach of compiling Lua to machine code (rather than luac + bin2c). * Streamline the interface between C and Lua code and allow efficient access to C datatypes from Lua (see Pyrex above). * Compile Lua to optimized C. For example, by statically determining that certain variables are used in a restricted way (e.g. by decorating the Lua source file with pragmas or determining this implicitly by inference), certain code constructs might be simplified to use plain C rather that the Lua C API. This could allow certain Lua code written with sufficient care to run at native speeds. Since it compiles to C, it will even work on CPUs where LuaJIT is not available. == Limitations / Status == WARNING: This code passes much of the Lua 5.1 test suite [7] and can compile itself, but the code is new and there can still be errors. In particular, a few language features (e.g. coroutines) are not implemented. See comments in lua2c.lua for details. Please report bugs/patches on the wiki. lua2c does not currently support coroutines, functions that normally reject C functions (e.g. setfenv), and possibly tail call optimizations. Not all of these have the exact analogue in C. Coroutines might not ever be supported. However, some solutions might be explored [8][9], including possibly generating code that maintains the coroutine context in Lua tables. Closures and upvalues are implemented, but creating and accessing upvalues is somewhat slow due to the implementation (see implementation notes below) and hopefully can be improved. Once the code is more complete/robust, more attention can be given to optimizing the code generation. Performance was 25%-75% of regular Lua when running a few tests [11], but hopefully future optimizations will improve that. == Lua 5.2 Notes == Note: LuaFiveTwo (as of 5.2.0-work4) deprecates getfenv and setfenv, which eliminates one of the limitations above. LuaFiveTwo has new lua_arith and lua_compare C API function, which eliminate the need for lua2c to reimplement these functions. LuaFiveTwo also has new lua_yieldk, lua_callk, and lua_pcallk functions for coroutines and might help to implement coroutines in lua2c. == Project Page == The project page is currently http://lua-users.org/wiki/LuaToCee . == Download == * Latest development source (recommended): http://github.com/davidm/lua2c/ . From here you can browse the source, download a tar/zip snapshot, or checkout with git by running "{{git clone git://github.com/davidm/lua2c.git}}". * Last release distribution: (see Project Page above) == Licensing == (c) 2008 David Manura. Licensed under the same terms as Lua (MIT license). See included LICENSE file for full licensing details. Please post any patches/improvements. == References == * [1] Metalua AST - http://metalua.luaforge.net/manual006.html#toc17 * [2] luac2c (previously named luatoc) - LuaList:2006-07/msg00144.html * [3] LHF's lua2c for Lua 4.0 - LuaList:2002-01/msg00296.html * [4] luagen++ - LuaGenPlusPlus * [5] Pyrex - http://www.cosc.canterbury.ac.nz/greg.ewing/python/Pyrex/ * [6] Clue - http://cluecc.sourceforge.net/ * [7] Lua 5.1 test suite - http://www.inf.puc-rio.br/~roberto/lua/lua5.1-tests.tar.gz * [8] Wikipedia:Coroutine - Implementations for C http://en.wikipedia.org/wiki/Coroutine#Implementations_for_C * [9] Coco - http://luajit.org/coco.html Coco - True C coroutine semantics (used in LuaJIT) * [10] BinToCee - http://lua-users.org/wiki/BinToCee * [11] The Computer Language Benchmarks Game http://shootout.alioth.debian.org/gp4/lua.php * http://lua-users.org/wiki/LuaImplementations - other source translators and Lua reimplementations
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