Is there way to change MATCH_LIMIT settings for PCRE?

[hont512]

Since LUA is often use in time-critical applications like web-servers, slow regexps could be fatal and MATCH_LIMIT settings should solve it.

I see nothing about it in lrexlib docs.

[shmuz]

It is supported.
One way is to supply the desired value of "execution flags" (see Lrexlib manual).
Another way is to specify flags in the pattern (a quote from PCRE manual follows):

A value for the match limit may also be supplied by an item at the start of a pattern of the form
(*LIMIT_MATCH=d) where d is a decimal number.

[hont512]

Thank you very much

I dig in the flags way but didn't succeed since these flags take parameters for itself and "execution flags" field takes just bitwised flags

My thoughts were like this, but it is not correct:

local F = rex.flags()
local ef = F.EXTRA_MATCH_LIMIT | F.EXTRA_MATCH_LIMIT_RECURSION
local subject = "ABCD"
local pattern = "B.D"
rex.match(subject, pattern, 1, nil, ef, 10000, 15000)

[shmuz]

@hont512, you seem to be right. Lrexlib provides no means to user to modify pcre_extra struct that is passed as an argument to pcre_exec.

I'll try to study this issue more in depth (and it must take some time).

[shmuz]

@hont512
Adding extra flags and parameters would complicate the Lrexlib API (which is already pretty complicated).

So if the default built-in PCRE limits for MATCH_LIMIT and MATCH_LIMIT_RECURSION seem too big in some specific use case, they can be overridden by specifying (*LIMIT_MATCH=d)and/or (*LIMIT_RECURSION=d) in the pattern (where d is decimal number).