EINTR on recvfrom() - how to block the signal?

[der Mouse]

In article <77135 at bu.edu.bu.edu>, jdubb at bucsf.bu.edu (jay dubb) writes:
> I have recvfrom() call in my code that attempts to read a UDP socket
> message, and is returning -1 and setting errno to EINTR - interrupted
> system call (as far as I can tell, this is the signal caused by one
> of the child processes dying).  What exactly does an interrupted
> recvfrom() do?

Nothing, I would hope and expect.  It depends on your system, of course
(you don't say what sort of machine or OS variant is in question).

> Can I temporarily disable signal delivery around the call (but making
> sure the signal is delivered after the call completes)?

Since recvfrom() is a socket call, I assume you're on a Berkeley
variant, in which case you should have sigblock() and sigsetmask(),
which should allow precisely that.

> If so, is this a good idea, provided I want to catch the message, and
> the signal also?

Unless you have experiments showing it doesn't work, I would recommend
just going back and doing the recvfrom() again when you get EINTR.  If
that is known to fail, blocking the signal in question is reasonable.

					der Mouse

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