向lua 5.2源添加可选的“全局”关键字

Question

I'd like to modify the lua 5.2 source code to allow for an optional "global" keyword to precede global variable declarations. Has any done this or does anyone know how to do this (safely)? And yes I am aware that variables are global by default and that this would be purely syntactic sugar.

To be clear, adding custom keywords of existing types is straight forward. The part I'm at a loss for is how to safely edit the parser (via the 5.2 C source code) so that it discards or ignores the new "global" keyword.

Answer 1

See this discussion for details and a proposed patch (against 5.3): http://lua.2524044.n2.nabble.com/Say-No-to-global-by-default-summary-of-the-discussion-td7683658.html . It uses a different (non-keyword based) approach, but should be a good starting point.

Answer 2

Figured it out. First I appended a new token TK_GLOBAL to the end of the RESERVED enum.

Then in luaX_init() I added...

ts = luaS_new(L, "global");
luaS_fix(ts);
ts->tsv.reserved = cast_byte(TK_GLOBAL+1-FIRST_RESERVED);

And finally in the statement() function I added...

case TK_GLOBAL:
   luaX_next(ls);
break;

As far as I can tell it works. Hopefully it's safe.