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From: Markus Elfring <Markus.Elfring@web.de>
Newsgroups: comp.programming.threads,comp.unix.programmer
Subject: Re: Safe accesses of global arrays in signal handlers?
Date: Sun, 30 Sep 2012 14:04:32 +0200
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> What do you mean by shared?

A global variable as the one that is used in your small source code example.
(Its data will be reused by other functions after it was eventually set by a
signal handler.)


> For example, assigning to an element of a file scoped array like this should be fine:

I have got doubts here.
https://www.securecoding.cert.org/confluence/display/seccode/SIG31-C.+Do+not+access+or+modify+shared+objects+in+signal+handlers


> 	volatile sig_atomic_t foo[NSIG];
> 
> 	void handler(int signo) {
> 		foo[signo] = 1;
> 	}

The access for a specific single integer can be performed atomically. Does this
situation change when the shown index is involved?
Do C/C++ compilers deal with pointer arithmetic in this use case which might
result in a portability issue?
Do any implementations or software platforms exist which guarantee that the
property "async-signal-safety" will be maintained here?

Regards,
Markus