==================== Read Lua Source Code

Reading Lua_ code is fairly easy. The language is simple, well documented, has a official book, a package manager and plenty of resources online.

The thing is, there is not a lot of resources explaining how to read the lua source code, which is a work of art on its own and a great way to study low level software design. This project attempts to put together suggestions and material that might help you read the lua source code in a timely fashion.

The material available here is mostly the work and suggestions of other people compiled in a single place. Few free to point out if something is mentioned without a source or send merge requests with more material.

.. _official book: https://www.lua.org/docs.html#books .. _The language is simple: https://devhints.io/lua .. _well documented: https://www.lua.org/docs.html

What Do You Need To Know

The Lua source code is written in ANSI C_, a low level, statically typed programming language very common as a base for software that should live very close to the hardware.

So, the first thing you should learn is the C language. Below there are some resources you could try these:

Online material

• learn-c_
• coursera c-programming_
• guru99 c-programming-tutorial_
• programiz c-programming_
• tutorialspoint c programming_
• ucam teaching C_
• ravi lua5.3 bytecode reference_
• ravi lua parsing and code generation_

.. _ravi lua5.3 bytecode reference: https://the-ravi-programming-language.readthedocs.io/en/latest/lua_bytecode_reference.html .. _ravi lua parsing and code generation: https://the-ravi-programming-language.readthedocs.io/en/latest/lua-parser.html

Books

• "C Programming Absolute Beginner's Guide" by Greg Perry and Dean Mille
• "The C Programming Language" by Brain W.
• "The C Programming Language" by Kernighan
• "C Programming: A Modern Approach" by Taschenbuch

List compiled from guru99_.

.. _guru99: https://www.guru99.com

Articles

• A No-Frills Introduction to Lua 5.1 VM Instructions_
• The Implementation of Lua 5.0_

.. _The Implementation of Lua 5.0: https://www.researchgate.net/profile/Roberto_Ierusalimschy/publication/220349489_The_Implementation_of_Lua_50/links/02e7e52403a963d32c000000.pdf .. _A No-Frills Introduction to Lua 5.1 VM Instructions: http://luaforge.net/docman/83/98/ANoFrillsIntroToLua51VMInstructions.pdf

Where To Start

Know where to start is very important, because you need to build the knowledge in your mind to put all the pieces together. Mimemike published a suggestion in this reddit post_ that I'll copy below:

• lmathlib.c, lstrlib.c: get familiar with the external C API. Don't bother with the pattern matcher though. Just the easy functions.
• lapi.c: Check how the API is implemented internally. Only skim this to get a feeling for the code. Cross-reference to lua.h and luaconf.h as needed.
• lobject.h: tagged values and object representation. skim through this first. you'll want to keep a window with this file open all the time.
• lstate.h: state objects. ditto.
• lopcodes.h: bytecode instruction format and opcode definitions. easy.
• lvm.c: scroll down to luaV_execute, the main interpreter loop. see how all of the instructions are implemented. skip the details for now. reread later.
• ldo.c: calls, stacks, exceptions, coroutines. tough read.
• lstring.c: string interning. cute, huh?
• ltable.c: hash tables and arrays. tricky code.
• ltm.c: metamethod handling, reread all of lvm.c now.
• You may want to reread lapi.c now.
• ldebug.c: surprise waiting for you. abstract interpretation is used to find object names for tracebacks. does bytecode verification, too.
• lparser.c, lcode.c: recursive descent parser, targetting a register-based VM. start from chunk() and work your way through. read the expression parser and the code generator parts last.
• lgc.c: incremental garbage collector. take your time.
• Read all the other files as you see references to them. Don't let your stack get too deep though.

Happy reading! Please, share your results and suggestions!

.. ANSI C: https://en.wikipedia.org/wiki/C(programming_language) .. _coursera c-programming: https://coursera.org/specializations/c-programming .. _guru99 c-programming-tutorial: https://www.guru99.com/c-programming-tutorial.html .. _learn-c: https://www.learn-c.org/ .. _Lua: https://www.lua.org/ .. _package manager: https://luarocks.org/ .. _programiz c-programming: https://www.programiz.com/c-programming .. _this reddit post: https://www.reddit.com/r/programming/comments/63hth/ask_reddit_which_oss_codebases_out_there_are_so/c02pxbp/ .. _tutorialspoint c programming: https://www.tutorialspoint.com/cprogramming/index.htm .. _ucam teaching C: http://www-h.eng.cam.ac.uk/help/tpl/languages/C/teaching_C/teaching_C.html