>> So it should be perfectly legal to call printf() from a signal
>> handler which is carefully blocked around calls to unsafe functions,
>> because this does not fall in the exception above, no?
> It is not legal.  Each invocation of the "unsafe" function needs to
> be protected from being interrupted by a signal for this to work.

Right.  "...which is carefully blocked around calls to unsafe
functions".

> Unfortunately you cannot predict which "unsafe" function might call
> another "unsafe" function, so you'll have to protect all of them.

Right.  "...which is carefully blocked around calls to unsafe
functions".  Not "...around calls to that function".

As I read it, Pavel was right: it's perfectly legal to call printf()
from a signal handler provided you make sure that the signal in
question can never be delivered during a call to an unsafe function
(printf or other).

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