Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #381615 > unrolled thread

Is this defined behavior?

Back to article view | Back to comp.lang.c

Contents

  Is this defined behavior? Anthony Cuozzo <anthony@cuozzo.us> - 2024-02-02 10:56 -0500
    Re: Is this defined behavior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-02-02 08:28 -0800
      Re: Is this defined behavior? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-02-03 00:44 -0800
        Re: Is this defined behavior? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-03 16:07 +0000
          Re: Is this defined behavior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-02-03 13:41 -0800
            Re: Is this defined behavior? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-04 03:18 +0000
              Re: Is this defined behavior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-02-03 19:48 -0800
                Re: Is this defined behavior? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-04 04:34 +0000
          Re: Is this defined behavior? David Brown <david.brown@hesbynett.no> - 2024-02-04 13:24 +0100
            Re: Is this defined behavior? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-04 15:16 +0000
              Re: Is this defined behavior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-02-04 13:31 -0800
                Re: Is this defined behavior? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-04 23:18 +0000
                  Re: Is this defined behavior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-02-04 15:56 -0800
                    Re: Is this defined behavior? gazelle@shell.xmission.com (Kenny McCormack) - 2024-02-05 00:05 +0000
                  Re: Is this defined behavior? Poprocks <please@replytogroup.com> - 2024-02-05 13:35 -0500
                    Re: Is this defined behavior? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-06 13:10 +0000
                    Is this sane behavior? (Was: Is this defined behavior?) gazelle@shell.xmission.com (Kenny McCormack) - 2024-02-06 14:52 +0000
                      Re: Is this sane behavior? (Was: Is this defined behavior?) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-06 15:50 +0000
                Re: Is this defined behavior? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-02-04 23:21 -0800
            Re: Is this defined behavior? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2024-02-04 15:27 +0000
              Re: Is this defined behavior? David Brown <david.brown@hesbynett.no> - 2024-02-04 18:23 +0100

Page 1 of 2  [1] 2  Next page →

#381615 — Is this defined behavior?

Time T: Add N to a uintptr_t

Time T+1: Subtract N from that same uintptr_t

Questions:

1. Is this behavior defined?

2. If it is, then will I be guaranteed to get back the same void * value 
I cast to uintptr_t?

Thank you,
--Anthony

[toc] | [next] | [standalone]

#381617

Anthony Cuozzo <anthony@cuozzo.us> writes:
> Time T: Add N to a uintptr_t
>
> Time T+1: Subtract N from that same uintptr_t
>
> Questions:
>
> 1. Is this behavior defined?

Sure, why wouldn't it be?  uintptr_t is just an unsigned integer type.
The guarantees about converting to and from void* don't affect its
arithmetic behavior.  Adding and then subtracting N yields the original
value.

> 2. If it is, then will I be guaranteed to get back the same void *
> value I cast to uintptr_t?

If the result of the conversion is a valid pointer value, yes.  In
particular, if the original value is the result of converting a valid
void* value, the guarantee in the standard applies:

    The following type designates an unsigned integer type with the
    property that any valid pointer to void can be converted to this
    type, then converted back to pointer to void, and the result will
    compare equal to the original pointer:

    uintptr_t

Adding and subtracting N between the conversions is well defined.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Medtronic
void Void(void) { Void(); } /* The recursive call of the void */

[toc] | [prev] | [next] | [standalone]

#381661

Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:

> Anthony Cuozzo <anthony@cuozzo.us> writes:
>
>> Time T:  Add N to a uintptr_t
>>
>> Time T+1:  Subtract N from that same uintptr_t
>>
>> Questions:
>>
>> 1.  Is this behavior defined?
>
> Sure, why wouldn't it be?  uintptr_t is just an unsigned integer
> type.  The guarantees about converting to and from void* don't
> affect its arithmetic behavior.  Adding and then subtracting N
> yields the original value.

Extremely likely to hold.  A perverse implementation could choose
(IIANM) a uintptr_t whose integer conversion rank is less than
that of int, and that could mess things up.  In practical terms
though what you say is spot on.

[toc] | [prev] | [next] | [standalone]

#381687

On 03/02/2024 08:44, Tim Rentsch wrote:
> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
> 
>> Anthony Cuozzo <anthony@cuozzo.us> writes:
>>
>>> Time T:  Add N to a uintptr_t
>>>
>>> Time T+1:  Subtract N from that same uintptr_t
>>>
>>> Questions:
>>>
>>> 1.  Is this behavior defined?
>>
>> Sure, why wouldn't it be?  uintptr_t is just an unsigned integer
>> type.  The guarantees about converting to and from void* don't
>> affect its arithmetic behavior.  Adding and then subtracting N
>> yields the original value.
> 
> Extremely likely to hold.  A perverse implementation could choose
> (IIANM) a uintptr_t whose integer conversion rank is less than
> that of int, and that could mess things up.  In practical terms
> though what you say is spot on.

OK, so this is completely topical and there's no issue there. But it's 
also fair to say that it's the sort of post which gives the newgroup a 
bad reputation.

I'm not going to take a position. But since we've had complaints about 
the diection things are going in, other people might like to weigh in on 
this.

-- 
Check out Basic Algorithms and my other books:
https://www.lulu.com/spotlight/bgy1mm

[toc] | [prev] | [next] | [standalone]

#381707

Malcolm McLean <malcolm.arthur.mclean@gmail.com> writes:
> On 03/02/2024 08:44, Tim Rentsch wrote:
>> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>>> Anthony Cuozzo <anthony@cuozzo.us> writes:
>>>> Time T:  Add N to a uintptr_t
>>>>
>>>> Time T+1:  Subtract N from that same uintptr_t
>>>>
>>>> Questions:
>>>>
>>>> 1.  Is this behavior defined?
>>>
>>> Sure, why wouldn't it be?  uintptr_t is just an unsigned integer
>>> type.  The guarantees about converting to and from void* don't
>>> affect its arithmetic behavior.  Adding and then subtracting N
>>> yields the original value.
>> Extremely likely to hold.  A perverse implementation could choose
>> (IIANM) a uintptr_t whose integer conversion rank is less than
>> that of int, and that could mess things up.  In practical terms
>> though what you say is spot on.
>
> OK, so this is completely topical and there's no issue there. But it's
> also fair to say that it's the sort of post which gives the newgroup a 
> bad reputation.
>
> I'm not going to take a position. But since we've had complaints about
> the diection things are going in, other people might like to weigh in
> on this.

What on Earth are you talking about?

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Medtronic
void Void(void) { Void(); } /* The recursive call of the void */

[toc] | [prev] | [next] | [standalone]

#381719

On 03/02/2024 21:41, Keith Thompson wrote:
> Malcolm McLean <malcolm.arthur.mclean@gmail.com> writes:
>> On 03/02/2024 08:44, Tim Rentsch wrote:
>>> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>>>> Anthony Cuozzo <anthony@cuozzo.us> writes:
>>>>> Time T:  Add N to a uintptr_t
>>>>>
>>>>> Time T+1:  Subtract N from that same uintptr_t
>>>>>
>>>>> Questions:
>>>>>
>>>>> 1.  Is this behavior defined?
>>>>
>>>> Sure, why wouldn't it be?  uintptr_t is just an unsigned integer
>>>> type.  The guarantees about converting to and from void* don't
>>>> affect its arithmetic behavior.  Adding and then subtracting N
>>>> yields the original value.
>>> Extremely likely to hold.  A perverse implementation could choose
>>> (IIANM) a uintptr_t whose integer conversion rank is less than
>>> that of int, and that could mess things up.  In practical terms
>>> though what you say is spot on.
>>
>> OK, so this is completely topical and there's no issue there. But it's
>> also fair to say that it's the sort of post which gives the newgroup a
>> bad reputation.
>>
>> I'm not going to take a position. But since we've had complaints about
>> the diection things are going in, other people might like to weigh in
>> on this.
> 
> What on Earth are you talking about?
> 
It's objectively the case that this sort of post gives the ng a bad 
reputation. But we don't necessarily have to care what other people 
think. So I'm not criticising Tim for this. I'm not saying that the post 
should not have been made. I'm not taking a position.

But the issue of sort of material we wish to see has been raised, and as 
regular contributor myself, I'm interested in what other people think. 
Is this the sort of material you wish to see? I'm interested in views. 
Including yours.
-- 
Check out Basic Algorithms and my other books:
https://www.lulu.com/spotlight/bgy1mm

[toc] | [prev] | [next] | [standalone]

#381720

Malcolm McLean <malcolm.arthur.mclean@gmail.com> writes:
> On 03/02/2024 21:41, Keith Thompson wrote:
>> Malcolm McLean <malcolm.arthur.mclean@gmail.com> writes:
>>> On 03/02/2024 08:44, Tim Rentsch wrote:
>>>> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>>>>> Anthony Cuozzo <anthony@cuozzo.us> writes:
>>>>>> Time T:  Add N to a uintptr_t
>>>>>>
>>>>>> Time T+1:  Subtract N from that same uintptr_t
>>>>>>
>>>>>> Questions:
>>>>>>
>>>>>> 1.  Is this behavior defined?
>>>>>
>>>>> Sure, why wouldn't it be?  uintptr_t is just an unsigned integer
>>>>> type.  The guarantees about converting to and from void* don't
>>>>> affect its arithmetic behavior.  Adding and then subtracting N
>>>>> yields the original value.
>>>> Extremely likely to hold.  A perverse implementation could choose
>>>> (IIANM) a uintptr_t whose integer conversion rank is less than
>>>> that of int, and that could mess things up.  In practical terms
>>>> though what you say is spot on.
>>>
>>> OK, so this is completely topical and there's no issue there. But it's
>>> also fair to say that it's the sort of post which gives the newgroup a
>>> bad reputation.
>>>
>>> I'm not going to take a position. But since we've had complaints about
>>> the diection things are going in, other people might like to weigh in
>>> on this.
>> What on Earth are you talking about?
>> 
> It's objectively the case that this sort of post gives the ng a bad
> reputation.

Nonsense.

[snip more nonsense]

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Medtronic
void Void(void) { Void(); } /* The recursive call of the void */

[toc] | [prev] | [next] | [standalone]

#381722

On 04/02/2024 03:48, Keith Thompson wrote:
> Malcolm McLean <malcolm.arthur.mclean@gmail.com> writes:
>> On 03/02/2024 21:41, Keith Thompson wrote:
>>> Malcolm McLean <malcolm.arthur.mclean@gmail.com> writes:
>>>> On 03/02/2024 08:44, Tim Rentsch wrote:
>>>>> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>>>>>> Anthony Cuozzo <anthony@cuozzo.us> writes:
>>>>>>> Time T:  Add N to a uintptr_t
>>>>>>>
>>>>>>> Time T+1:  Subtract N from that same uintptr_t
>>>>>>>
>>>>>>> Questions:
>>>>>>>
>>>>>>> 1.  Is this behavior defined?
>>>>>>
>>>>>> Sure, why wouldn't it be?  uintptr_t is just an unsigned integer
>>>>>> type.  The guarantees about converting to and from void* don't
>>>>>> affect its arithmetic behavior.  Adding and then subtracting N
>>>>>> yields the original value.
>>>>> Extremely likely to hold.  A perverse implementation could choose
>>>>> (IIANM) a uintptr_t whose integer conversion rank is less than
>>>>> that of int, and that could mess things up.  In practical terms
>>>>> though what you say is spot on.
>>>>
>>>> OK, so this is completely topical and there's no issue there. But it's
>>>> also fair to say that it's the sort of post which gives the newgroup a
>>>> bad reputation.
>>>>
>>>> I'm not going to take a position. But since we've had complaints about
>>>> the diection things are going in, other people might like to weigh in
>>>> on this.
>>> What on Earth are you talking about?
>>>
>> It's objectively the case that this sort of post gives the ng a bad
>> reputation.
> 
> Nonsense.
> 
> [snip more nonsense]
> 
Bless.
You've been invited to give your view. If you won't do so, I hope you 
won't blame me if therefore your views don't count.
-- 
Check out Basic Algorithms and my other books:
https://www.lulu.com/spotlight/bgy1mm

[toc] | [prev] | [next] | [standalone]

#381732

On 03/02/2024 17:07, Malcolm McLean wrote:
> On 03/02/2024 08:44, Tim Rentsch wrote:
>> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>>
>>> Anthony Cuozzo <anthony@cuozzo.us> writes:
>>>
>>>> Time T:  Add N to a uintptr_t
>>>>
>>>> Time T+1:  Subtract N from that same uintptr_t
>>>>
>>>> Questions:
>>>>
>>>> 1.  Is this behavior defined?
>>>
>>> Sure, why wouldn't it be?  uintptr_t is just an unsigned integer
>>> type.  The guarantees about converting to and from void* don't
>>> affect its arithmetic behavior.  Adding and then subtracting N
>>> yields the original value.
>>
>> Extremely likely to hold.  A perverse implementation could choose
>> (IIANM) a uintptr_t whose integer conversion rank is less than
>> that of int, and that could mess things up.  In practical terms
>> though what you say is spot on.

An 8-bit implementation with very limited RAM might use 8-bit pointers, 
at least for "normal" pointers.  (Typically such systems also support 
extensions such as "far" pointers, or "code memory" pointers.)  I 
haven't seen such an implementation, but it is certainly conceivable. 
("int" would be 16-bit.)

> 
> OK, so this is completely topical and there's no issue there. But it's 
> also fair to say that it's the sort of post which gives the newgroup a 
> bad reputation.
> 

No, it is the kind of thing that gives this group a /good/ reputation.

People with questions about C behaviour can come here and ask, and get 
considered answers.  In particular, they get answers from people who 
look carefully at the standards - not just one or two implementations. 
They tell you about uncommon situations that others might not have 
considered - including uncommon real implementations, and also possible 
implementations.  For people who want to write code that they /know/ 
works, and /know/ is correct even if it is used on other platforms, this 
kind of information is invaluable.

For people who are happy with "I tried it and it worked on my compiler 
on my machine", it is of little interest.

If this newsgroup were filled with nothing but discussions about C 
standard minutiae, it would be boring to many people - and yet still a 
value resource for people to visit when they need to.  But it is not 
filled with that - it is an important aspect of the group, but not the 
only one.


The validity of pointers as they are converted or arithmetic is applied 
is of huge interest, and is a significant area of research in language 
design and compiler design.  There is a lot of work being done on 
"pointer providence" - where pointers come from, and what they can point 
to.   Knowing what, if anything, they can point to, and whether there 
are aliases, is massively relevant to code correctness and optimisation 
opportunities for compilers.

If you don't care about any of this, that's fine - skip the thread.  But 
let the people that do care talk about these things.

> I'm not going to take a position. But since we've had complaints about 
> the diection things are going in, other people might like to weigh in on 
> this.
> 

You /have/ taken a position, and you /have/ criticised Tim for his post 
- by making this complaint.

[toc] | [prev] | [next] | [standalone]

#381739

On 04/02/2024 12:24, David Brown wrote:
> 
> You /have/ taken a position, and you /have/ criticised Tim for his post 
> - by making this complaint.
> 

Other people have made that complaint. I'm not making it myself. But 
other people have said this, so it is therefore an issue.

I want other people's views, and thnk you for giving yours.
-- 
Check out Basic Algorithms and my other books:
https://www.lulu.com/spotlight/bgy1mm

[toc] | [prev] | [next] | [standalone]

#381759

Malcolm McLean <malcolm.arthur.mclean@gmail.com> writes:
> On 04/02/2024 12:24, David Brown wrote:
>> You /have/ taken a position, and you /have/ criticised Tim for his
>> post - by making this complaint.
>
> Other people have made that complaint. I'm not making it myself. But
> other people have said this, so it is therefore an issue.
>
> I want other people's views, and thnk you for giving yours.

You haven't given your views.  You've just falsely claimed that it's
"also fair to say that it's the sort of post which gives the newgroup a
bad reputation".

I think you're trying to start an argument while pretending to be above
the fray.  I don't know or care why.

If you have something to say about what was wrong with Tim's post,
you're free to say it.  If not, please drop this -- and I suggest that
others not take the bait.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Medtronic
void Void(void) { Void(); } /* The recursive call of the void */

[toc] | [prev] | [next] | [standalone]

#381770

On 04/02/2024 21:31, Keith Thompson wrote:
> Malcolm McLean <malcolm.arthur.mclean@gmail.com> writes:
>> On 04/02/2024 12:24, David Brown wrote:
>>> You /have/ taken a position, and you /have/ criticised Tim for his
>>> post - by making this complaint.
>>
>> Other people have made that complaint. I'm not making it myself. But
>> other people have said this, so it is therefore an issue.
>>
>> I want other people's views, and thnk you for giving yours.
> 
> You haven't given your views.  You've just falsely claimed that it's
> "also fair to say that it's the sort of post which gives the newgroup a
> bad reputation".
> 
> I think you're trying to start an argument while pretending to be above
> the fray.  I don't know or care why.
> 
> If you have something to say about what was wrong with Tim's post,
> you're free to say it.  If not, please drop this -- and I suggest that
> others not take the bait.
> 

I know that this is hard for you because you your psychological type.
But try to step think back and think what the reaction of a perfectly 
normal person might be if, coming to the ng for the first time, that was 
the first post he read. Then think what other people have said on 
related subjects, and whether or not it is an objective reality, 
independent of my opinion, whether or not that has been said.

However I am not myself personally either the hypothetical person coming 
to the ng for the first time, nor the actual and indisputably existent 
person who I am thinking of especially. I'm not the source of the 
complaints.

But of course the complaint is that whilst the point made might be true 
if you intepret the C stnadard in a literal sense, it is so unlikely 
that anyone would implement such a compiler, or even think of doing so, 
that it is abusrd. And so the ng does get a bad reputation. Objectively 
and not just in my opinion. And whilst I am think especially of one 
person, he's not saying something which is eccentric, or not level 
headed. But I'm holding judgement on whether that is fair, or if it 
matters. If other people hold us in contempt, is that a big issue, if we 
enjoy discussing what we discuss?

Tim complained about other people's content, including but not 
especially mine. So it's only fair if we now discuss his content. 
However I don't want to complain about it. I don't see it as a simple 
and open and shut issue like that. And I don't want to antagonise. I 
think we've far too much antognistic behaviour going on at the moment 
and its time to try to out a stop to it.
-- 
Check out Basic Algorithms and my other books:
/////
https://www.lulu.com/spotlight/bgy1mm

[toc] | [prev] | [next] | [standalone]

#381775

Malcolm McLean <malcolm.arthur.mclean@gmail.com> writes:
[...]
> I know that this is hard for you because you your psychological type.
[...]

Go away.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Medtronic
void Void(void) { Void(); } /* The recursive call of the void */

[toc] | [prev] | [next] | [standalone]

#381777

In article <87o7cvlr6e.fsf@nosuchdomain.example.com>,
Keith Thompson  <Keith.S.Thompson+u@gmail.com> wrote:
>Malcolm McLean <malcolm.arthur.mclean@gmail.com> writes:
>[...]
>> I know that this is hard for you because you your psychological type.
>[...]
>
>Go away.

Very mature.

And about what we expect from your psychological type.

-- 
The randomly chosen signature file that would have appeared here is more than 4
lines long.  As such, it violates one or more Usenet RFCs.  In order to remain
in compliance with said RFCs, the actual sig can be found at the following URL:
	http://user.xmission.com/~gazelle/Sigs/RightWingMedia

[toc] | [prev] | [next] | [standalone]

#381840

On 2024-02-04, Malcolm McLean wrote:
> On 04/02/2024 21:31, Keith Thompson wrote:
[snip]
>> You haven't given your views.  You've just falsely claimed that it's
>> "also fair to say that it's the sort of post which gives the newgroup a
>> bad reputation".
>> 
>> I think you're trying to start an argument while pretending to be above
>> the fray.  I don't know or care why.
>> 
>> If you have something to say about what was wrong with Tim's post,
>> you're free to say it.  If not, please drop this -- and I suggest that
>> others not take the bait.
>> 
>
> I know that this is hard for you because you your psychological type.
> But try to step think back and think what the reaction of a perfectly 
> normal person might be if, coming to the ng for the first time, that was 
> the first post he read. Then think what other people have said on 
> related subjects, and whether or not it is an objective reality, 
> independent of my opinion, whether or not that has been said.
[snip]

I'm not exactly coming to this ng for the first time, but I've been a
casual occasional reader at best and am coming back to it after a long
while. The original parent thread was the first thread that looked
interesting to me, and I read it and gained some knowledge.

And then I spent 10 minutes of my life I'll never get back, reading this
bizarre, passive-aggressive flamebait.

*plonk*

[toc] | [prev] | [next] | [standalone]

#381918

On 05/02/2024 18:35, Poprocks wrote:
> On 2024-02-04, Malcolm McLean wrote:
>> On 04/02/2024 21:31, Keith Thompson wrote:
> [snip]
>>> You haven't given your views.  You've just falsely claimed that it's
>>> "also fair to say that it's the sort of post which gives the newgroup a
>>> bad reputation".
>>>
>>> I think you're trying to start an argument while pretending to be above
>>> the fray.  I don't know or care why.
>>>
>>> If you have something to say about what was wrong with Tim's post,
>>> you're free to say it.  If not, please drop this -- and I suggest that
>>> others not take the bait.
>>>
>>
>> I know that this is hard for you because you your psychological type.
>> But try to step think back and think what the reaction of a perfectly
>> normal person might be if, coming to the ng for the first time, that was
>> the first post he read. Then think what other people have said on
>> related subjects, and whether or not it is an objective reality,
>> independent of my opinion, whether or not that has been said.
> [snip]
> 
> I'm not exactly coming to this ng for the first time, but I've been a
> casual occasional reader at best and am coming back to it after a long
> while. The original parent thread was the first thread that looked
> interesting to me, and I read it and gained some knowledge.
> 
> And then I spent 10 minutes of my life I'll never get back, reading this
> bizarre, passive-aggressive flamebait.
> 
> *plonk*

I should point out that meta posts about the newsgroup itself are topical.
-- 
Check out Basic Algorithms and my other books:
https://www.lulu.com/spotlight/bgy1mm

[toc] | [prev] | [next] | [standalone]

#381922 — Is this sane behavior? (Was: Is this defined behavior?)

In article <slrnus2ak7.rmg.please@loganrpi.rathbonelaw.com>,
Poprocks  <please@replytogroup.com> whined:
...
>And then I spent 10 minutes of my life I'll never get back, reading this
>bizarre, passive-aggressive flamebait.

And then you spent 20 minutes of your life you'll never get back, posting
the above bizarre, passive-aggressive flamebait.

-- 
'Islamaphobia' is a term created by fascists and used by cowards to manipulate morons.

    - Author unknown, quoted by Sam Harris -

[toc] | [prev] | [next] | [standalone]

#381923 — Re: Is this sane behavior? (Was: Is this defined behavior?)

On 06/02/2024 14:52, Kenny McCormack wrote:
> In article <slrnus2ak7.rmg.please@loganrpi.rathbonelaw.com>,
> Poprocks  <please@replytogroup.com> whined:
> ...
>> And then I spent 10 minutes of my life I'll never get back, reading this
>> bizarre, passive-aggressive flamebait.
> 
> And then you spent 20 minutes of your life you'll never get back, posting
> the above bizarre, passive-aggressive flamebait.
> 
It's self refuting. And the use of technical pyschiatric terms they 
don't really understand as an insult is very trademark.
-- 
Check out Basic Algorithms and my other books:
https://www.lulu.com/spotlight/bgy1mm

[toc] | [prev] | [next] | [standalone]

#381798

Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:

>> [... some discussion regarding a posting of mine and alleged
>>      reactions to it ...]
>
> If you have something to say about what was wrong with Tim's post,
> you're free to say it.  If not, please drop this -- and I suggest
> that others not take the bait.

Thank you for this summary.  I second your suggestion.

[toc] | [prev] | [next] | [standalone]

#381740

David Brown <david.brown@hesbynett.no> writes:

> On 03/02/2024 17:07, Malcolm McLean wrote:
>> On 03/02/2024 08:44, Tim Rentsch wrote:
>>> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>>>
>>>> Anthony Cuozzo <anthony@cuozzo.us> writes:
>>>>
>>>>> Time T:  Add N to a uintptr_t
>>>>>
>>>>> Time T+1:  Subtract N from that same uintptr_t
>>>>>
>>>>> Questions:
>>>>>
>>>>> 1.  Is this behavior defined?
>>>>
>>>> Sure, why wouldn't it be?  uintptr_t is just an unsigned integer
>>>> type.  The guarantees about converting to and from void* don't
>>>> affect its arithmetic behavior.  Adding and then subtracting N
>>>> yields the original value.
>>>
>>> Extremely likely to hold.  A perverse implementation could choose
>>> (IIANM) a uintptr_t whose integer conversion rank is less than
>>> that of int, and that could mess things up.  In practical terms
>>> though what you say is spot on.
>
> An 8-bit implementation with very limited RAM might use 8-bit pointers, at
> least for "normal" pointers.  (Typically such systems also support
> extensions such as "far" pointers, or "code memory" pointers.)  I haven't
> seen such an implementation, but it is certainly conceivable. ("int" would
> be 16-bit.)

I think you are suggesting that uintptr_t might, on such a system, be
only 8 bits wide, but that's no permitted.  UINTPTR_MAX can be no less
than 2**16 - 1.  Of course that alone does not prevent its rank being
less that that of int, but the system you describe would not be an
example.

-- 
Ben.

[toc] | [prev] | [next] | [standalone]

Page 1 of 2  [1] 2  Next page →

Back to top | Article view | comp.lang.c

csiph-web