async-signal-safe functions (was: patch adding a pidfile-option to script(1))

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

It's interesting how one can learn interesting things when discussing 
as seemingly unrelated topic.

> In other words, you can safely call a non-async-signal-safe function
> from a signal handler _if_ you can guarantee that it won't interrupt
> any non-async-signal-safe function.
So "async-signal-safe" means sort of "re-entrant", but not only for one 
single function itself, but for the whole lot of it?