[Bug libstdc++/61601] C++11 regex resource exhaustion

[timshen at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61601

--- Comment #7 from Tim Shen <timshen at gcc dot gnu.org> ---
(In reply to Maksymilian Arciemowicz from comment #6)
> > Do you have any other testcases?
> 
> for trunk? maybe you have to use ::regex_match

std::regex_match("findme", std::regex("(.*{100}{200}findme)"));

there's no memory problem, it just takes exponentially long time to run (which
is expected when using backtracking).

To avoid it, you can use Thompson NFA:

#define _GLIBCXX_REGEX_USE_THOMPSON_NFA
#include <regex>

int main (int argc, char *argv[])
{
  std::regex_match("findme", std::regex("(.*{100}{200}findme)",
std::regex_constants::extended));

  return 0;

}

Notice that for now Thompson NFA doesn't support ECMAScript.