doSafeLog is called when logging itself runs into a reentrancy or throws an exception. We currently write a line directly to std::cerr in those situations, but the contents of that line are pretty obscure. Just something line "ERROR(12345) Assertion". There's no indication on std::cerr what generated this line.

Lots more information is available, like timestamp, threadname, etc.
In personal debugging efforts for SERVER-109030 (but it could be anything), I enhanced this messaging to see what was going on and it was helpful. I'd like to commit what I came up with as a separate PR, hence this ticket.