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RUNTIME.md

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What Lua dialect is this?

This is a custom build of LuaJIT 2.1, which means the base language is Lua 5.1 plus the following extensions:

How it was built

  • package.path and package.cpath looks only in the SDK for modules.
  • built with -pthread so that pthread.lua can be used.
  • built with -msse4.2.

How to run Lua scripts with it

$ path-to-sdk/bin/linux/luajit        myapp.lua
> path-to-sdk\bin\windows\luajit.exe  myapp.lua

How to make portable apps with it

A portable app is one that runs from any current directory (CWD). For that to work all the files that are loaded by the app at runtime must be looked for in locations that are relative to the app's directory. That includes modules loaded by require(), shared libraries loaded by the OS, as well as any assets, config files, etc. that the app loads.

The LuaJIT executable is already set up to find Lua modules and shared libraries from the SDK independent of CWD, but it doesn't know anything about your app's directory layout.

To enable require() to look for Lua modules in your app's directory too, call luapath(scriptdir()) (use luacpath() for Lua/C modules).

If your app also contains shared libraries, you need to make the OS aware of their location. You can't just give absolute paths to ffi.load() because if your shared libraries also depend on (that is, are dynamically linked to) other shared libraries, it's the OS that has to load those, not LuaJIT. The fix is to either call sopath() before loading shared libraries from your app dir, or call ffi.load with absolute paths on all dependencies to preload them.

As for other files that you load explicitly, just make sure to only use paths that are relative to scriptdir() (eg. use indir(scriptdir(), 'rel path')).

Changing CWD to scriptdir() from the beginning (chdir(scriptdir())) and using only relative paths throughout the app also works if you can make sure that the CWD will not be changed afterwards from other parts of the app.