Support ruby 2.2 and lua 5.3

[sobrinho]

Hi,

I'm going to try to add this support on rlua but I never wrote any line of C, so, I may need some help.

[whitequark]

OK

[sobrinho]

Lua 5.1 is working on ruby 2.1.5p273 but to be honest, I'm complete lost on the C code :flushed:

Seems like the C API on Lua 5.2 has changed and changing the rlua.c:

#include <ruby.h>
#include <lua5.2/lua.h>
#include <lua5.2/lauxlib.h>
#include <lua5.2/lualib.h>
#include <ctype.h>

And trying to install obviously fails:

λ sudo gem install pkg/rlua-1.1.beta1.gem
Building native extensions.  This could take a while...
ERROR:  Error installing pkg/rlua-1.1.beta1.gem:
        ERROR: Failed to build gem native extension.

    /usr/bin/ruby2.1 -r ./siteconf20150223-6630-7u238i.rb extconf.rb
checking for luaL_newstate() in -llua5.2... yes
creating Makefile

make "DESTDIR=" clean

make "DESTDIR="
compiling rlua.c
In file included from /usr/include/ruby-2.1.0/ruby.h:33:0,
                 from rlua.c:1:
rlua.c: In function ‘rlua_load_string’:
/usr/include/ruby-2.1.0/ruby/ruby.h:1121:30: error: too few arguments to function ‘lua_load’
 #define RSTRING(obj) (R_CAST(RString)(obj))
                              ^
/usr/include/ruby-2.1.0/ruby/ruby.h:1115:30: note: in definition of macro ‘R_CAST’
 #define R_CAST(st)   (struct st*)
                              ^
/usr/include/ruby-2.1.0/ruby/ruby.h:848:6: note: in expansion of macro ‘RSTRING’
      RSTRING(str)->as.heap.ptr)
      ^
rlua.c:187:66: note: in expansion of macro ‘RSTRING_PTR’
   int retval = lua_load(state, rlua_reader, (void*) interm_code, RSTRING_PTR(chunkname));
                                                                  ^
In file included from rlua.c:2:0:
/usr/include/lua5.2/lua.h:261:16: note: declared here
 LUA_API int   (lua_load) (lua_State *L, lua_Reader reader, void *dt,
                ^
make: *** [rlua.o] Error 1

make failed, exit code 2

Gem files will remain installed in /var/lib/gems/2.1.0/gems/rlua-1.1.beta1 for inspection.
Results logged to /var/lib/gems/2.1.0/extensions/x86_64-linux/2.1.0/rlua-1.1.beta1/gem_make.out

Can you take a look?

I will probably need some days to understand how C works and what has changed on Lua C API.

[sobrinho]

What I got so far is that lua_load has changed from this to this.

I will try to fix it but do not trust me hahahahahaha!

[whitequark]

Just add a NULL as the last argument.

[sobrinho]

It compiled but now when running the examples on README:

λ irb
(main) normal> require 'rlua'
=> true
(main) normal> 
(main) statement_continue> state = Lua::State.new   # create Lua interpreter
=> #<Lua::State:0x00000001d6f500 @state=#<Object:0x00000001d6f4d8 @refs={}, @procs=[]>>
(main) normal> state.__load_stdlib :all # load some standard libraries in it
=> true
(main) normal> state.__eval "print('hello, world')" # launch some Lua code
hello, world
=> nil
(main) normal> state.value = 10            # set a variable in Ruby
irb: symbol lookup error: /var/lib/gems/2.1.0/gems/rlua-1.1.beta1/lib/rlua.so: undefined symbol: lua_getfenv

Looking at 5.2 manual, has this:

Pseudoindex LUA_ENVIRONINDEX and functions lua_getfenv/lua_setfenv were removed, as C functions no longer have environments.

This function is used here: https://github.com/whitequark/rlua/blob/18738ef14666e2007800f0c067ae5c95a882ed87/ext/rlua.c#L678

[sobrinho]

I think I will be useful writing a test suite in ruby to ensure we don't break anything on ruby API on that change (from 5.1 to 5.2).

Would be helpful?

[whitequark]

Yeah, sure. Looking at getfenv, the functionality was removed but rlua does not depend on it. You can just remove __env binding. If you actually need to fetch the environment it looks like that can only be done with the debug library.

[krissi]

Great that you picked this up! Is there already a public branch with your work?

I suggest to use a versioning scheme including the Lua version to be able to depend on a specific version. For example .. (51.1.1 for the current version)