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Re: volatile in struct member

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Malcolm McLean <malcolm.mclean5@btinternet.com> writes:

> On Friday, September 30, 2016 at 12:54:19 PM UTC+1, Thiago Adams wrote:
>> Can this make sense?
>> 
>> struct 
>> {
>>   volatile int i;
>> };
>> 
> It makes perfect sense. The member must never be stored in a register
> but read from memory and written back at every operation.

Though (probably not intentionally) the OP has made a struct that has no
tag and is not part of a declaration of some objects, so there can never
be a member to read and written from memory!

But I suspect the question is more about the placement of the keyword.
I'd put the volatile on the object declaration:

  struct small { int i; };
  volatile struct small sm;

So I think what's being asked is if there is any reason ever to put in
in the struct rather than on the declared object.  A more detailed
example might have used a mixed structure like this:

 struct mixed {
     int i;
     volatile int v;
     char bytes[8];
 };

where you can't get the same effect by volatile qualifying an object of
the this type.

> I think it is also allowed.

In general, yes, though the exact example given is not useful.

-- 
Ben.

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Thread

volatile in struct member Thiago Adams <thiago.adams@gmail.com> - 2016-09-30 04:52 -0700
  Re: volatile in struct member Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-30 05:50 -0700
    Re: volatile in struct member Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-30 14:42 +0100
      Re: volatile in struct member Gareth Owen <gwowen@gmail.com> - 2016-09-30 22:09 +0100
        Re: volatile in struct member Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-30 22:24 +0100
  Re: volatile in struct member Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-30 14:29 +0100
    Re: volatile in struct member David Brown <david.brown@hesbynett.no> - 2016-09-30 16:22 +0200
      Re: volatile in struct member Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-30 15:51 +0100
        Re: volatile in struct member David Brown <david.brown@hesbynett.no> - 2016-09-30 17:07 +0200
    Re: volatile in struct member Tim Rentsch <txr@alumni.caltech.edu> - 2016-10-08 15:48 -0700
  Re: volatile in struct member David Brown <david.brown@hesbynett.no> - 2016-09-30 15:36 +0200
    Re: volatile in struct member Thiago Adams <thiago.adams@gmail.com> - 2016-09-30 06:47 -0700
      Re: volatile in struct member James Kuyper <jameskuyper@verizon.net> - 2016-09-30 12:53 -0400
        Re: volatile in struct member supercat@casperkitty.com - 2016-09-30 10:18 -0700
          Re: volatile in struct member raltbos@xs4all.nl (Richard Bos) - 2016-09-30 20:57 +0000
            Re: volatile in struct member supercat@casperkitty.com - 2016-09-30 14:46 -0700
        Re: volatile in struct member Thiago Adams <thiago.adams@gmail.com> - 2016-09-30 10:22 -0700
          Re: volatile in struct member jameskuyper@verizon.net - 2016-09-30 14:08 -0700

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