64f679e9   
   From: ike@sverige.freeshell.org   
      
   On 2012-10-19, Gil N.  wrote:   
   > C standard is indeed more terse and when read ad litteram it seems   
   > to allow unsequenced 'volatile access' to non volatile objects.   
   >   
   > however,   
   > "any expression referring to such an object shall be evaluated   
   > strictly according to the rules of the abstract machine, as described   
   > in 5.1.2.3" (6.7.3) - all my quotes are from C standard.   
   >   
   > imagine this:   
   >   
   > {   
   >   int a = 0;   
   >   int volatile * pa = &a;   
   >   int volatile * pb = pa + pa;    /*(1)*/   
      
   Addition of pointers is an invalid operation in C and in C++.   
      
   >   int b = *pa + *pa;              /*(2)*/   
   > }   
   >   
   > remember that evaluation of an expression is value evaluation and   
   > initiation of side effects. in (1) evaluating pa has side effects.   
   > in (2) evaluating '*pa' with effective non volatile type must obey   
   > the rules of abstract machine because it is an evaluation of an   
   > (sub)expression referring to a volatile object 'pa'.   
      
      
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