Why does std::regex_iterator cause a stack overflow with this data?

Question

I\'ve been using std::regex_iterator to parse log files. My program has been working quite nicely for some weeks and has parsed millions of log lines, until to

Answer 1

The regex appears to be OK; at least there is nothing in it that could cause catastrophic backtracking.

I see a small possibility to optimize the regex, cutting down on stack use:

static wregex rgx_log_lines(
    L"^L(\\d+)\\s+"             // Level
    L"T(\\d+)\\s+"              // TID
    L"(\\d+)\\s+"               // Timestamp
    L"\\[([\\w:]+)\\]"          // Function name
    L"((?:"                     // Complex pattern
      L"(?!"                    // Stop matching when...
        L"^L\\d"                // New log statement at the beginning of a line
      L")"                      
      L"[^]"                    // Matching all until then
    L")*)"                      // 
    );

Did you set the ECMAScript option? Otherwise, I suspect the regex library defaults to POSIX regexes, and those don't support lookahead assertions.