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From: David Brown <david.brown@hesbynett.no>
Newsgroups: comp.lang.c
Subject: Re: int a = a (Was: Bart's Language)
Date: Thu, 20 Mar 2025 15:57:48 +0100
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On 20/03/2025 10:02, Tim Rentsch wrote:
> scott@slp53.sl.home (Scott Lurndal) writes:

>> I would disagree with this last statement.  (void)x is genuinely
>> useful and has no ill side effects.   'int a = a;' is exactly
>> the opposite - not useful and has potenial bad side effects.
> 
> I concur except that I recommend using (void)&x rather than (void)x,
> because (void)&x is safer.  If x is volatile qualified, for example,
> the expression (void)x actually does something, and must not be
> compiled away, whereas (void)&x does not have these properties.

I would recommend knowing which variables are volatile and which are 
not, so that the issue does not arise.

Casting a volatile variable to void does "something", but what that 
"something" is is implementation-defined and can vary between compilers. 
  Doing things to volatiles other than clear, simple reads or writes is 
a risk - the semantics are not fully defined in the C standards, 
implementations vary, and it is not at all uncommon for implementations 
to be inconsistent or buggy in that area.  This is why C++ has 
deprecated many uses of volatile objects.  So if you actually want to 
read a volatile variable but ignore the results (as you might well want 
to do for hardware device registers), it's best to do :

	auto dummy = volatile_var;
	(void) dummy;

rather than

	(void) volatile_var;