https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86164
std::regex crashes when matching long lines.

Here is an example:

#include <regex>
#include <iostream>
 
int main()
{
    std::string s (100'000, '*');
    std::smatch m;
    std::regex r ("^(.*?)$");

    std::regex_search (s, m, r);

    std::cout << s.substr (0, 10) << std::endl;
    std::cout << m .str (1) .substr (0, 10) << std::endl;
}

It turns out that std::regex_search operator .* is implemented recursively which result in this example in a stack overflow.

Goal

• Investigate how much benefit we can get from small changes that just reduce stack layout.
• Investigate replacing recursion with iteration
• Investigate transforming NFA to DFA (probably not possible without ABI change)