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Signals

v4	v5
63	63	When using foreign libraries through the Haskell FFI, it is important
64	64	to ensure that the foreign code is capable of dealing with system call
65		interrupts due to alarm signals. For example, in this `strace` output
	65	interrupts due to alarm signals. Most C libraries we deal with don't install signal handlers, so this is a not an issue. However, if the C library does install a signal handler, you'll
	66	need to be careful how it interprets the time signal from GHC.
	67
	68	For example, in this `strace` output
66	69	a `select` call is interrupted, but the foreign C code interprets the
67	70	interrupt as an application error and closes a critical file
…	…
69	72
70	73	{{{
71		[pid 22338] send(7, "\1\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 116, MSG_NOSIGNAL) = 116
	74	[pid 22338] send(7, "\1\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0
	75	\0\0\0\0\0\0\0\0\0\0\0"..., 116, MSG_NOSIGNAL) = 116
72	76	[pid 22338] select(8, [7], NULL, NULL, NULL) = ? ERESTARTNOHAND (To be restarted)
73	77	[pid 22338] --- SIGVTALRM (Virtual timer expired) @ 0 (0) ---
…	…
80	84
81	85	Once the C code was modified to deal with the interrupt properly, it
82		proceeded correctly:
	86	proceeded correctly (note that foreign call is restarted 3 times before it succeeds).
83	87
84	88	{{{