Re: Every sufficiently competent C programmer knows

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.
--
Mikko