luaproc.newproc() can now take a lua function as an argument

[scythe]

This pull request modifies the behavior of luaproc.newproc to handle the case where it is passed a pure Lua function as an argument. The advantages of passing a Lua function reference instead of a chunk of Lua code are:

• Syntax checking happens when the file is loaded, rather than when the process is created. This is especially useful if the process is not created until some time has passed after startup.
• Syntax highlighting is available in most editors for functions at top-level, but not for functions in longstrings. Most linting and static analysis tools, e.g. luacheck, also do not handle functions in longstrings.
• If the function is very long and/or many processes are to be created, using a precompiled chunk saves a significant amount of time parsing/compiling the Lua code.
• Passing a function to luaproc.newproc() mirrors the behavior of coroutine.create() and is more intuitive for new users.

Of note, using string.dump() like this: luaproc.newproc(string.dump(myfunction)) does not work now and did not work before either, because lua_loadstring() assumes that the chunk it is passed is null-terminated, which means that a bytecode chunk passed from string.dump() would often be cut off and generate a binary string: truncated precompiled chunk error. The rewritten luaproc_create_newproc() uses strlen() to get the length of code for lua_loadbuffer(), which also expects null-termination, but I didn't think it was a concern because passing a function directly is simpler and it works, and obviously nobody was using string.dump() anyway or they would have noticed the errors.

tests/hello.lua was also modified to demonstrate both the new and old behavior.

Thanks for continuing to maintain this so many years later 👍

[scythe]

Update:

• Add a macro #if LUA_VERSION_NUM >= 503 to use the new 4-argument lua_dump() on Lua 5.3.
• Aesthetic stuff, move stuff to follow the sectional layout of luaproc.c, some comments, formatting.

[askyrme]

Thanks for the suggestion. Passing functions as arguments to newproc indeed has advantages and we are interested in incorporating this functionality in the next upcoming release. We are reviewing your patch and will get back to you once we have finished evaluating how to merge its functionality into luaproc.

[scythe]

Cool, thanks. I read about your experiment with transactional memory, shame it didn't work out; I guess there's some updates behind the scenes that we haven't seen here yet?

Leave a comment here if you want me to fix anything.

[askyrme]

Mason, thank you once again for your suggestions. I just pushed a new version of luaproc that allows luaproc.newproc to receive Lua functions as arguments; binary strings also work fine now. I used your patch as a basis for the implementation, but I changed it to (a) handle function upvalues and (b) use the standard Lua string buffer structure -- luaL_Buffer -- to avoid handling memory allocation from luaproc.

[scythe]

Awesome! Congratulations on the new release.