From: robin_listas@es.invalid   
      
   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.   
      
      
      
   --   
   Cheers,   
           Carlos E.R.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)