From: jameskuyper@alumni.caltech.edu   
      
   On 2026-01-03 23:52, Lawrence D’Oliveiro wrote:   
   > On Sat, 3 Jan 2026 21:31:20 -0500, James Kuyper wrote:   
   >   
   >> On 2026-01-03 21:19, Lawrence D’Oliveiro wrote:   
   >>>   
   >>> What if the entire machine address space is valid? Are C pointer   
   >>> types supposed to add an extra “invalid” value on top of that?   
   >>   
   >> Either that, or set aside one piece of addressable memory that is   
   >> not available to user code. Note, in particular, that it might be a   
   >> piece of memory used by the implementation of C, or by the operating   
   >> system. In which case, the undefined behavior that can occur as a   
   >> result of dereferencing a null point would take the form of messing   
   >> up the C runtime or the operating system.   
   >   
   > “Undefined behaviour” could also include “performing a valid memory   
   > access”, could it not.   
      
   Of course. In fact, the single most dangerous thing that can occur when   
   code with undefined behavior is executed is that it does exactly what   
   you incorrectly believe it is required to do. As a result, you fail to   
   be warned of the error in your beliefs.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)