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Re: volatile in struct member

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On 30/09/16 15:29, Ben Bacarisse wrote:
> Thiago Adams <thiago.adams@gmail.com> writes:
> 
>> Can this make sense?
>>
>> struct 
>> {
>>   volatile int i;
>> };
> 
> People sometimes use volatile to alter the way the optimiser works, so
> whilst that may not "make sense" in any portable way, I'd not want to
> rule it out.
> 
>> Why this question?  
>> I was just trying to find some qualifier to hijack and put other
>> concept on it to use in static analysis if the generated code isn't
>> affected.
>>
>> For curiosity, I tried:
>>
>> struct 
>> {
>>   register int i1; //error
>>   auto int i2; //error
>>   restrict i3; //error
>>  
>> }
> 
> register and auto are storage class specifiers like static.  volatile is
> a type qualifier (like const and restrict).  The difference is that type
> qualifiers go in the declarator and can be mixed in with *s and []s and
> so on:
> 
>    register auto   long long   *const p;
>    |------------|  |-------|   |------|
>    storage class     type     declarator
> 

I would say that the key difference is that storage class specifiers
affect the placement, lifetime, linkage and scope of the object, while
the qualifiers affect how the object is accessed.  Thus it can make
sense to access different parts of a struct in different ways (const,
volatile), but it does not make sense to have different parts of the
struct have different lifetimes or be in different places.

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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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