Invoking writeln() from a lot of threads running concurrently --> crash

[Walter Bright]

On 12/9/2017 5:56 AM, Seb wrote:
> IIRC the implementation of LockingTextWriter 
> isn't thread-safe.

There's no bugzilla issue on this. So I added one:

   https://issues.dlang.org/show_bug.cgi?id=18052

Please, folks, I can't emphasize this enough. When you find a bug, POST IT ON 
BUGZILLA! Otherwise, it will NEVER get fixed.