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Do this program have the specified behavior?

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  Do this program have the specified behavior? olcott <NoOne@NoWhere.com> - 2021-11-16 21:33 -0600
    Re: Do this program have the specified behavior? wij <wyniijj@gmail.com> - 2021-11-16 20:10 -0800
      Does this program have the specified behavior? olcott <NoOne@NoWhere.com> - 2021-11-16 22:46 -0600
        Re: Does this program have the specified behavior? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-11-16 21:12 -0800
          Re: Does this program have the specified behavior? olcott <NoOne@NoWhere.com> - 2021-11-17 08:33 -0600
        Re: Does this program have the specified behavior? Richard Damon <Richard@Damon-Family.org> - 2021-11-17 06:53 -0500
          Re: Does this program have the specified behavior? olcott <NoOne@NoWhere.com> - 2021-11-17 08:49 -0600
            Re: Does this program have the specified behavior? Juha Nieminen <nospam@thanks.invalid> - 2021-11-18 06:32 +0000
              Re: Does this program have the specified behavior? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-11-18 11:15 +0000
                Re: Does this program have the specified behavior? olcott <NoOne@NoWhere.com> - 2021-11-18 08:59 -0600
              Re: Does this program have the specified behavior? olcott <NoOne@NoWhere.com> - 2021-11-18 08:58 -0600
        Re: Does this program have the specified behavior? Anurag Ranjan <anuragranjan630@gmail.com> - 2021-11-17 22:00 +0000

#82369 — Do this program have the specified behavior?

#include <stdint.h>
typedef void (*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.


-- 
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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#82370

On Wednesday, 17 November 2021 at 11:33:49 UTC+8, olcott wrote:
> #include <stdint.h> 
> typedef void (*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. 
> 
> 
> -- 
> Copyright 2021 Pete Olcott 
> 
> Talent hits a target no one else can hit; 
> Genius hits a target no one else can see. 
> Arthur Schopenhauer

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

[]$ g++ t.cpp              
t.cpp: In function ‘int H(ptr, ptr)’:
t.cpp:6:2: error: too many arguments to function
    6 | x(y); // direct execution of P(P)
      | ~^~~
t.cpp: In function ‘int main()’:
t.cpp:18:3: error: invalid conversion from ‘int (*)(ptr)’ {aka ‘int (*)(void (*)())’} to ‘ptr’ {aka ‘void (*)()’} [-fpermissive]
   18 | H(P, P);
      |   ^
      |   |
      |   int (*)(ptr) {aka int (*)(void (*)())}
t.cpp:4:11: note:   initializing argument 1 of ‘int H(ptr, ptr)’
    4 | int H(ptr x, ptr y)
      |       ~~~~^
t.cpp:18:6: error: invalid conversion from ‘int (*)(ptr)’ {aka ‘int (*)(void (*)())’} to ‘ptr’ {aka ‘void (*)()’} [-fpermissive]
   18 | H(P, P);
      |      ^
      |      |
      |      int (*)(ptr) {aka int (*)(void (*)())}
t.cpp:4:18: note:   initializing argument 2 of ‘int H(ptr, ptr)’
    4 | int H(ptr x, ptr y)
      |              ~~~~^

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#82371 — Does this program have the specified behavior?

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++


-- 
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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#82372 — Re: Does this program have the specified behavior?

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...

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#82374 — Re: Does this program have the specified behavior?

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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#82373 — Re: Does this program have the specified behavior?

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.

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#82375 — Re: Does this program have the specified behavior?

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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#82377 — Re: Does this program have the specified behavior?

In comp.lang.c++ olcott <NoOne@nowhere.com> wrote:
>>> typedef int (*ptr)();
>>>
>>> int H(ptr x, ptr y)
>>> {
>>>     x(y); // direct execution of P(P)
>>>     return 1;
>>> }
> 
> This code does compile and run correctly.

It might compile as C, but it shouldn't compile as C++, because it's trying
to call an int(*)() with a parameter, even though that function (that the
pointer is pointing to does not take any parameter.)

Perhaps if it were an int(*)(void*) and then you reinterpret-cast the
parameter in order to call it, then it would compile.

As for "runs correctly", I don't see how this "runs correctly". Unless you
mean an infinite recursion that does nothing "runs correctly".

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#82378 — Re: Does this program have the specified behavior?

Juha Nieminen <nospam@thanks.invalid> writes:

> In comp.lang.c++ olcott <NoOne@nowhere.com> wrote:
>>>> typedef int (*ptr)();
>>>>
>>>> int H(ptr x, ptr y)
>>>> {
>>>>     x(y); // direct execution of P(P)
>>>>     return 1;
>>>> }
>> 
>> This code does compile and run correctly.
>
> It might compile as C, but it shouldn't compile as C++, because it's trying
> to call an int(*)() with a parameter, even though that function (that the
> pointer is pointing to does not take any parameter.)

Just as it must not compile in C++, this code must compile in C.  The
meaning of empty ()s in a function declaration is different between the
two languages.

When I tidied up the code, I wrote C, not C++, because C has a more
suitable type available.

-- 
Ben.

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#82380 — Re: Does this program have the specified behavior?

On 11/18/2021 5:15 AM, Ben Bacarisse wrote:
> Juha Nieminen <nospam@thanks.invalid> writes:
> 
>> In comp.lang.c++ olcott <NoOne@nowhere.com> wrote:
>>>>> typedef int (*ptr)();
>>>>>
>>>>> int H(ptr x, ptr y)
>>>>> {
>>>>>      x(y); // direct execution of P(P)
>>>>>      return 1;
>>>>> }
>>>
>>> This code does compile and run correctly.
>>
>> It might compile as C, but it shouldn't compile as C++, because it's trying
>> to call an int(*)() with a parameter, even though that function (that the
>> pointer is pointing to does not take any parameter.)
> 
> Just as it must not compile in C++, this code must compile in C.  The
> meaning of empty ()s in a function declaration is different between the
> two languages.
> 
> When I tidied up the code, I wrote C, not C++, because C has a more
> suitable type available.
> 

You did a really great job.

-- 
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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#82379 — Re: Does this program have the specified behavior?

On 11/18/2021 12:32 AM, Juha Nieminen wrote:
> In comp.lang.c++ olcott <NoOne@nowhere.com> wrote:
>>>> typedef int (*ptr)();
>>>>
>>>> int H(ptr x, ptr y)
>>>> {
>>>>      x(y); // direct execution of P(P)
>>>>      return 1;
>>>> }
>>
>> This code does compile and run correctly.
> 
> It might compile as C, but it shouldn't compile as C++, because it's trying
> to call an int(*)() with a parameter, even though that function (that the
> pointer is pointing to does not take any parameter.)
> 
> Perhaps if it were an int(*)(void*) and then you reinterpret-cast the
> parameter in order to call it, then it would compile.
> 
> As for "runs correctly", I don't see how this "runs correctly". Unless you
> mean an infinite recursion that does nothing "runs correctly".
> 

This is the question that I am asking:

Does this program have the specified behavior?
For every H that simulates or executes its input and aborts or does not
abort its input P never reaches its last instruction.

-- 
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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#82376 — Re: Does this program have the specified behavior?

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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