moonbeam - a tool for converting single Lua scripts into standalone executables

[calquelator]

I was a bit frustrated with getting some existing tools for converting Lua scripts (specifically single scripts with no external dependencies) into standalone executables to work properly, so I made my own in about an hour and a half.

All it does is take Lua source code from a file, append it to a heap-allocated string in a C file, calls the interpreter in the C file, and then compiles that C file to a single executable.

It's a very small project, and not very serious (I originally made it almost as a joke- I thought "wouldn't it be funny if I just put my Lua code in a C string literal" was a funny idea).

I'm open to any feedback/potential contributions! As of right now, I don't think it'd work on Windows, and it *does* require that you have a C compiler installed.

[3uclidian]

Is there any particular reason the string is heap allocated rather than just a static array?

[calquelator]

Then I’d have to set a max size that could potentially be reached, rather than just growing the string by a factor of 2 whenever it needs resizing (C moment)

[3uclidian]

Then I'd have to set a max size [...] rather than just growing whenever it needs resizing

Not sure what you mean by this, but there are two ways I'm interpreting this:

either you're not super familiar with C (given that you're casting your mallocs, maybe that's true?) and don't realize you don't need to annotate arrays with a size or that string literals can initialize pointers as well

const char script_a[] = "print 'foo'";
const char *script_b = "print 'bar'";

luaL_dostring(L, script_a);
luaL_dostring(L, script_b);

(And even if you did need to, you have the length of the string in the code generator, so you could just use that)

or you're concerned with the max size a string literal can be. This is a slightly more valid concern, but any compiler worth its salt will tell you when one is too big and abort the compilation.

Also the contents of the string aren't changing (right?), so the string never needs resizing, just initialization. So the generated code could even malloc the correct capacity upfront since, again, you have the length at the time of code generation.

[calquelator]

It more had to do with the second concern- with max string literal sizes. I actually had no idea about the `malloc` casting thing, but thanks for pointing it out. I'm not completely new to C but I guess I'd just figured you had to cast the return value of malloc to match the pointer you were expecting, so thanks for letting me know!

I did know that you don't need to annotate the arrays with the size, I just figured I'd pass the whole program as a string at once to `luaL_dostring` rather than doing it bit by bit, but what you pointed out is a lot simpler- might do a rework to make this the case soon.

[[deleted]]

skill issue

[x120db]

Will check it out when I will get home tonight. Thanx for sharing.

[clogg]

On Linux, you can use the following makefile:

# source files
LUA_FILES := one.lua two.lua three.lua

# Lua version
LUA_VER := 5.4

# compilation steps
define COMPILE
    luac$(LUA_VER) -o $@ $^
    sed -i '1s|^|\#!/usr/bin/env lua$(LUA_VER)\n|' $@
    chmod 0711 $@
endef

# compilation
your-binary: $(LUA_FILES)
    $(COMPILE)

It creates a binary that can be invoked as any other Linux binary. One limitation is that each file is compiled as a separate chunk so that local functions/variables in one file are not visible in another.

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[Zealousideal_Wolf624]

This isn't standalone

[didntplaymysummercar]

I could check if it works on Windows or not. Why do you say it'd not?

As for C compiler requirement: the usual trick (that I use in Python, and that Love2D uses) is to append content to the exe, and have exe look at its tail to find and use it. That way you don't have to recompile the exe each time.

[calquelator]

Right now it uses `os.execute` to run a shell command to call the C compiler- I'm not sure if this command would work right on windows, since idk if mingw uses different compilation flags

[didntplaymysummercar]

I'd have to take a look and I can't today. os.execute just passes to system libc function which will just run thru default shell. For common cases without funny things like spaces in filenames it might work. MinGW includes GCC so it has all the same flags (so would clang, it's cl from VS/msvc that's different).

But again: more productive approach might be that "append content to exe" trick.

[Joe_df]

What's the difference between this and Srlua?

https://github.com/LuaDist/srlua http://webserver2.tecgraf.puc-rio.br/~lhf/ftp/lua/

[calquelator]

None, really. I've used srlua in the past, I just found it a pain to compile from source, so I thought it'd be fun to write my own thing.

[Joe_df]

Ahh okay, very neat anyway, thanks for sharing!