boost regex regex_search crash

[ufwt@…]

i use tmp.txt size >5m, only one line include bbbbbbbb

use regex "[a-z].*(xxxxx)' and call regex_search

then boost throw except

[Steven Watanabe]

Can you provide minimal code and input that reproduces the problem? What exception is thrown exactly?

[ufwt@…]

crash example:

boost::regex re("[a-z].*(d_notexiststring)",boost::regex::perl|boost::regex::no_except);

std::string s="f"; s.append(1024*100,'a'); s.append("dd"); boost::match_results<std::string::const_iterator> what; boost::match_flag_type flags = boost::match_default;

std::string::const_iterator start, end; start = s.begin(); end = s.end(); boost::regex_search(start,end,what,re,flags);

except:

uncaught exception of type boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<std::runtime_error> >

• Memory exhausted

raise at state_count > max_state_count

[John Maddock]

The code doesn't crash: it throws an exception that it's documented to throw.

In this case it's because the number of states visited in the FSM has grown too large and it bails out to prevent an "eternal" match attempt.

Perl manages to optimise this particular expression, but if you make it trivially more complex, say '[a-z].*(xxxxx)|x', then it takes a very long time indeed to return from a match attempt on your string.

I'll leave this open for now though, as it looks like this special case can be optimised a little more.

John.

[ufwt@…]

so i use try catch to avoid program crash!!

[ufwt@…]

i also change re_repeat's max let re_pepeat max - min < 1024 i can change this ?

[anonymous]

"i also change re_repeat's max let re_pepeat max - min < 1024 i can change this ? "

Sorry I don't understand what you are asking. Change what code precisely?

[ufwt@…]

i chanage re_repeat'max , code:

void changeRegexRepeatNum(boost::regex &regex,size_t max) {

boost::re_detail::re_syntax_base* state=regex.get_data().m_first_state; while(state){

switch(state->type){

case boost::re_detail::syntax_element_rep: case boost::re_detail::syntax_element_dot_rep: case boost::re_detail::syntax_element_char_rep: case boost::re_detail::syntax_element_short_set_rep: case boost::re_detail::syntax_element_long_set_rep: {

boost::re_detail::re_repeat *repeat=static_cast<boost::re_detail::re_repeat*>(state); if(repeat->max - repeat->min >max){

repeat->max = repeat->min + max;

}

} break; default:

break;

} state = state->next.p;

}

[anonymous]

Sure you can do that, but I'm not sure why you would want to?

John.

[ufwt@…]

because my txt is very long ,i do this can regex_search speed quick!