From: invalid@invalid.invalid   
      
   The Natural Philosopher  writes:   
      
   > On 12/02/2026 18:52, Carlos E. R. wrote:   
   >> On 2026-02-12 18:23, Rich wrote:   
   >>> Carlos E. R.  wrote:   
   >>>> On 2026-02-12 13:38, The Natural Philosopher wrote:   
   >>>>> On 11/02/2026 22:24, Carlos E. R. wrote:   
   >>>>>> On 2026-02-11 19:50, Rich wrote:   
   >>>>>>> c186282  wrote:   
   >>>>>>>> On 2/10/26 04:09, The Natural Philosopher wrote:   
   >>>>>>>>> ...more fuel on the fire...   
   >>>>>>>>>   
   >>   
   >>>>> I think the point is that the compiler knows that isn't necessary, and   
   >>>>> doesnt bother.   
   >>>>>   
   >>>>   
   >>>> Then don't optimize. Optimization has always been somewhat problematic.   
   >>>> Sometimes it introduced bugs that could not be debugged, because   
   >>>> debugging altered the code, possibly removing the optimizations.   
   >>>   
   >>> It wasn't the optimizer causing the "skipping" of the rest of the   
   >>> checks.  It was a byproduct of boolean short-circuiting of boolean   
   >>> expressions.  Most languages only evaluate just enough of a complex   
   >>> boolean expression to reach a true or false indication, then skip the   
   >>> rest of the expression (yes, this is an 'optimization', but not by the   
   >>> code optimizer but the language specification itself).   
   >>>   
   >>> The skipping of the remaining character checks in the example posted   
   >>> here was due to this boolean short-circuit behavior.  Once the first   
   >>> 'false' arrived for the first incorrect character, the compiled code   
   >>> skipped over evaluating the boolean expression for subsequent   
   >>> characters.  So -O0 (no optimizations) or -O3 (full optimizations) made   
   >>> no difference, portions of the 'constant time execution' were skipped,   
   >>> opening a timing side channel attack.   
   >>   
   >> Ah, yes, I remember that now. Can play havoc when one of the   
   >> expression is actually a function and the later code relies on the   
   >> prior execution of that code.   
   >   
   > the keyword 'volatile' helps in this case   
      
   No. volatile does not affect the execution of the short-circuiting   
   boolean operators. If the left-hand side of && is false, or the left   
   hand side of || is true, then the right-hand is not executed.   
      
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   https://www.greenend.org.uk/rjk/   
      
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