TAU_TRACK_MEMORY_HEADROOM(3) on Linux
The text 63d800070980, as Debian 9 (Stretch), Debian 8 (Jessie), Debian 7 (Wheezy), Debian 6.0 (Squeeze), Debian 4.0 (Etch) shipped it. The page shows this text now.
Track the headroom (amount of memory for a process to grow) by periodically interrupting the program