Fast, lock-free, core-dumpable prints (meaning you can see not-yet-flushed prints in core dumps/live processes).
Basically a way to have a binary log buffer for real-time/low-level/kernel-level debugging that you then view as formatted text messages (instead of some type of struct array or whatever).
100+ LOC, more of example code than a "real" library at this point.
- dtest.cpp shows how to use dprintf - basically dprintf("i=%d\n", i); dflush();
- source test.sh shows how to convert raw log files to text, and how to extract the last log messages from core dumps or live processes (you use a user-defined gdb command dprintf and pass it a raw file, or get the last messages in the core/process if you don't pass a file).