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

[max at cert dot cx]

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

--- Comment #8 from Maksymilian Arciemowicz <max at cert dot cx> ---
> there's no memory problem, it just takes exponentially long time to run
> (which is expected when using backtracking).

call it cpu resource exhaustion (CWE-400)

> 
> 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.

yeap.

try (.*{300}{100}) for _GLIBCXX_REGEX_USE_THOMPSON_NFA. occurs stack exhaustion
like in #61582