From: arne@vajhoej.dk   
      
   On 8/15/2025 8:31 PM, John Reagan wrote:   
   > On 8/15/2025 7:48 PM, Arne Vajhøj wrote:   
   >> On 8/15/2025 1:33 PM, Simon Clubley wrote:   
   >>> On 2025-08-15, Dan Cross  wrote:   
   >>>> In article <107n93n$13rjm$1@dont-email.me>,   
   >>>> Simon Clubley   wrote:   
   >>>>> On 2025-08-12, Arne Vajhøj  wrote:   
   >>>>>>       if(args->arg_count == 2 && args->arg_type[0] ==   
   >>>>>> STRING_RESULT &&   
   >>>>>> args->arg_type[1] == INT_RESULT)   
   >>>>>   
   >>>>> Is it guaranteed that arg_type[] will always have at least elements ?   
   >>>>> If not, that's dangerous unless the compiler you are using does   
   >>>>> expression short-circuiting.   
   >>>>   
   >>>> C is well-defined in this regard.  Boolean expressions in C,   
   >>>> created by combining logical subexpressions with the `&&` and   
   >>>> `||` operators, are documented to use short-circuiting behavior.   
   >>   
   >>> Unless it's explicit in the language syntax itself, and given that   
   >>> I write code in multiple languages, I have long written code that   
   >>> assumes implicit[*] short-circuiting is not available.   
   >>>   
   >>> As such, whether implicit short-circuiting is available or not is   
   >>> not really that important to me, but I will admit I didn't realise   
   >>> C had it.   
   >>>   
   >>> [*] By implicit short-circuiting I mean something that's only defined   
   >>> in the language standard or implemented in a compiler, instead of some   
   >>> explicit syntax in the language itself to state short-circuiting is   
   >>> available.   
   >>   
   >> In general I like the idea of writing code in a way that does   
   >> not require the reader to have memorized ten thousand things from   
   >> the language spec.   
   >>   
   >> But I do not consider this a matter of remembering the specific   
   >> details about an operator - I consider this a matter of remembering   
   >> what operator a symbol represent.   
   >>   
   >> I consider "short circuiting AND" and "non short circuiting AND"   
   >> to be two different operators.   
   >   
   > BTW, while the C frontend always generates the "short-circuiting" AND   
   > and OR intermediate opcodes, the GEM optimizer works to detect if that   
   > is really needed.  It is hoping to hoist something from the right-hand   
   > side out of a loop (which happens more than you think) and on Itanium it   
   > can even put both left and right in the same bundle if possible (which   
   > doesn't happen all that much)   
      
   Keeping the pipeline busy ...   
      
   But there are two obvious issues to avoid:   
   * early test that must short circuit or later test will crash   
      (null pointer usage, array index out of range etc.)   
   * call of functions with side effects   
      
   Arne   
      
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