Re: list-lpeg and capture stack overflow

[Wesley Smith <wesley.hoke@...>]

On Thu, Jun 17, 2010 at 11:33 AM, Fabio Mascarenhas <mascarenhas@acm.org> wrote:
> Failures do an implicit close, so opens and closes may not be 1:1. And
> it would no cause a stack leak, anyway, as the current list is kept in
> the registry instead of the stack.

Good to know!

> I think the culprits are the runtime captures. The values returned by
> a runtime capture are kept indefinitely in the stack. If there are
> nested runtime captures then these values end up being replicated.
> This behavior is inherited from regular LPEG... I am trying to think
> of a way to fix it, but it is far from trivial.

I see.  This is actually a huge problem for me since everything has
nested Cmt captures.  I need these to check specific key-value pairs
in the tree of tables and there's no other way to do it.  What the
reasoning behind keeping around nested Cmt captures?

Also, I'm not 100% sure that this is actually the problem.  If I print
out the stack, I see the printout below after the match function runs.
 The first 6 values are obviously the setup before match is run.
Slots 7-15 are generated by match, however, the only captures
generated return a capture value of nil, so something else has to be
going on for each node in the table to be placed on the stack like
this.


1 userdata
2 table
	K:: number (1.000000)
	V: table
3 (-13): nil
4 (-12): lightuserdata (0xbfffa7d0)
5 table
	K:: number (1.000000)
	V:: string (_depth_first)
	K:: number (2.000000)
	V:: function (0xc48340)
	K:: number (3.000000)
	V:: string (B)
	K:: number (4.000000)
	V:: string (C)
	K:: number (5.000000)
	V:: string (B)
	K:: number (6.000000)
	V:: function (0xc48470)
	K:: number (7.000000)
	V:: string (_patt)
	K:: number (8.000000)
	V:: string (_depth_first)
	K:: number (9.000000)
	V:: function (0xc48550)
6 table
	K:: number (1.000000)
	V: table
	K:: number (2.000000)
	V: table
	K:: number (3.000000)
	V: table
	K:: number (4.000000)
	V: table
	K:: number (5.000000)
	V: table
	K:: number (6.000000)
	V: table
7 table
	K:: number (1.000000)
	V: table
	K:: number (2.000000)
	V: table
	K:: string (rule)
	V:: string (A)
8 table
	K:: number (1.000000)
	V:: string (C)
	K:: string (token)
	V:: string (C)
9 (-7): nil
10 table
	K:: number (1.000000)
	V:: string (C)
	K:: string (token)
	V:: string (C)
11 table
	K:: number (1.000000)
	V:: string (C)
	K:: string (token)
	V:: string (C)
12 table
	K:: number (1.000000)
	V: table
	K:: number (2.000000)
	V: table
	K:: string (rule)
	V:: string (A)
13 table
	K:: number (1.000000)
	V: table
	K:: number (2.000000)
	V: table
	K:: string (rule)
	V:: string (A)
14 table
	K:: number (1.000000)
	V: table
15 table
	K:: number (1.000000)
	V: table
nil