https://issues.dlang.org/show_bug.cgi?id=23395

          Issue ID: 23395
           Summary: Regex leaks memory when used in multithreaded
                    environment
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: minor
          Priority: P1
         Component: phobos
          Assignee: nobody@puremagic.com
          Reporter: qigezx+dc40d6nao940k@grr.la

Each thread where regular expressions are used leaks memory exactly once, I
think that only the first created regex leaks.
This is true for (CTR) compile time and runtime regex. CTR leak much more
memory. The leak grows or shrinks depending on the size of the regex.
Compile the following example with "ldc2 -fsan=address -g" to see for yourself.
It also works with gdc and dmd, but at least for dmd you need to use valgrind
instead, which is more ambigious and less informative in it's reporting for
this bug.
```
import std;

void threadFun(){
    auto rgx = regex(r"(?P<num>\d)");
    auto res = matchFirst(words, rgx);
    res["num"].writeln;
}

void main(){
    foreach(i; 0..10){
        task!(threadFun).executeInNewThread();
    }
}
```

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