Lua changes

waywall makes use of LuaJIT, an alternative implementation of Lua 5.1 which provides better performance and additional functionality. A list of LuaJIT's additions is available here.

Note: The ffi and jit packages from LuaJIT are not available in waywall.

Instruction count limit

waywall will allow a maximum of 50 million Lua instructions to be executed when it calls into user code (e.g. actions). This limit is in place to prevent buggy configurations from hard-locking waywall.

If this limit is exceeded, an error will be thrown, causing Lua execution to stop. This error cannot be caught with pcall or xpcall.

Standard library changes

waywall makes a few changes and additions to the Lua standard library:

• package.path is automatically updated to include the waywall configuration directory, so you can require() other files contained within it.
• pcall and xpcall have been modified to prevent user code from disabling the instruction count limit by accident.
• print has been modified so that its output appears in a similar format to other waywall log messages.
• os.setenv is a new function added by waywall which behaves much like C's setenv() and allows for changing and deleting environment variables.
  • Calling os.setenv with two strings (a name and value) will behave like C's setenv().
  • Calling os.setenv with a string and nil will unset the given environment variable.

There are also a few breaking changes, which are mostly intended to prevent user code from causing problems within waywall's address space:

• load, loadfile, and loadstring are not available

You can refer to the startup code to see all of the changes waywall makes in more detail.