XPost: comp.lang.c

On 11/17/2021 2:28 AM, Mark Bluemel wrote:

On Wednesday, 17 November 2021 at 05:13:08 UTC, Chris M. Thomasson wrote:

On 11/16/2021 8:46 PM, olcott wrote:

#include <stdint.h>
#include <stdio.h>
typedef int (*ptr)();

int H(ptr x, ptr y)
{
x(y); // direct execution of P(P)
return 1;
}

int P(ptr x)
{
H(x, x);
return 1;
}

int main(void)
{
H(P, P);
}

Stack overflow...

Surely a compiler can optimise this to remove the recursion, and for that matter, remove any functionality at all, as the code has no observable behaviour, as far as I can see (I'd be happy to be corrected on this!).

This is the question:
For every H that simulates or executes its input and aborts or does not
abort its input does any P ever reach its last instruction?

$DIETY only knows what olcott was trying to show with this code.

--
Copyright 2021 Pete Olcott

Talent hits a target no one else can hit;
Genius hits a target no one else can see.
Arthur Schopenhauer

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XPost: comp.lang.c

On 11/17/2021 5:53 AM, Richard Damon wrote:

On 11/16/21 11:46 PM, olcott wrote:

On 11/16/2021 10:10 PM, wij wrote:

On Wednesday, 17 November 2021 at 11:33:49 UTC+8, olcott wrote:

#include <stdint.h>
#include <stdio.h>
typedef int (*ptr)();

int H(ptr x, ptr y)
{
   x(y); // direct execution of P(P)
   return 1;
}

int P(ptr x)
{
   H(x, x);
   return 1;
}

int main(void)
{
   H(P, P);
}

For every H that simulates or executes its input and aborts or does not
abort its input P never reaches its last instruction.

I would guess yes, it is specified: BAD, illegal program

It must be compiled as C and the typedef was incorrect.
I can't find a way to specify the "C" calling convention for g++

Shows you don't understand C++.

Making it 'C' calling convention doesn't change the syntax for the call.

In C++, an empty parameter list specifies a void parameter list, while
in C it specifies tha mostly obsolete concept that this is a
non-prototype declaration that doesn't specify the parameters.

Ultimately the problem is that this runs into the issue that it is
impossible to express in C a function that takes or returns a pointer to
the same type as the function itself is, as that requires self
references in the type definition.

This code does compile and run correctly.
The only difference from Ben's code is that
void (*ptr)(); was changed to int (*ptr)();

In comp.lang.c On 11/11/2021 2:31 PM, Ben Bacarisse:
transformed my syntax into his syntax




--
Copyright 2021 Pete Olcott

Talent hits a target no one else can hit;
Genius hits a target no one else can see.
Arthur Schopenhauer

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XPost: comp.lang.c

On 17/11/2021 04:46, Wolcott wrote:

On 11/16/2021 10:10 PM, wij wrote:

On Wednesday, 17 November 2021 at 11:33:49 UTC+8, olcott wrote:

#include <stdio.h>

void count(int n)
{
static int d = 1;
printf("n = %d\n", n);
printf("d = %d\n", d);

d++;

if (n > 1)
{
count(n - 1);
}
printf("d = %d\n", d);
}
int main()
{
count(5);
return 0;
}

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