Re: Every sufficiently competent C programmer knows

On 2025-03-11 19:16:35 +0000, olcott said:

On 3/11/2025 9:02 AM, Mikko wrote:

On 2025-03-11 13:26:55 +0000, olcott said:
 

On 3/11/2025 5:01 AM, Richard Heathfield wrote:

On 11/03/2025 08:55, Fred. Zwarts wrote:

Op 11.mrt.2025 om 00:41 schreef olcott:

typedef void (*ptr)();
int HHH(ptr P);
 void Infinite_Loop()
{
   HERE: goto HERE;
   return;
}
 void Infinite_Recursion()
{
   Infinite_Recursion();
   return;
}
 void DDD()
{
   HHH(DDD);
   return;
}
 int DD()
{
   int Halt_Status = HHH(DD);
   if (Halt_Status)
     HERE: goto HERE;
   return Halt_Status;
}
 That when HHH correctly emulates N steps of the
above functions that none of these functions can
possibly reach their own "return" instruction
and terminate normally.

 

 Since HHH does see that same pattern that competent
C programmers see it correctly aborts its emulation
and rejects these inputs as non terminating.

 All competent C programmers see that HHH correctly reports that it cannot possibly reach the 'return' instruction.

 First, my credentials. I've been programming in C for over 35 years; I'm told that my book on C has been used on two undergraduate Comp Sci courses (one in the States and one in the UK); and I have my Knuth cheque. I don't claim to be any kind of programming guru, but I hope I do not overstate the case when I suggest that I can be regarded as competent not just as a programmer but specifically in the C language.
 And yet I can't even /see/ HHH, let alone judge what it does or does not do correctly. All I see is a call to it.

 It is stipulated that HHH correctly emulates N
steps of the x86 machine code of its input functions.
This may or may not include HHH emulating itself
emulating an input.

 The stipulation does not include the value of N (although a reasonable
interpretation is that it is finite). Nor does the stipulation specify
what HHH does after the emulation.
 

 It need not those are totally
irrelevant to the primary point:
 When HHH correctly emulates N steps of the
above functions none of these functions can
possibly reach their own "return" instruction
and terminate normally.

That's almost self-evident. Unless some special fieatures of C are used,
and none of these are used above, no other function can do anything when
one functin does something.

For HHH(DDD) and HHH(DD) it is stipulated that
HHH does correctly emulate itself emulating
these inputs.

But not that the emulation is complete, the emulation is discontinued
when the total step count is N.
--
Mikko