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From: Michael S <already5chosen@yahoo.com>
Newsgroups: comp.lang.c
Subject: Re: The difference between strtol() and strtoul() ?
Date: Sun, 23 Jun 2024 15:32:19 +0300
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On Sun, 23 Jun 2024 12:38:51 +0100
Ben Bacarisse <ben@bsb.me.uk> wrote:

> Michael S <already5chosen@yahoo.com> writes:
> 
> > On Fri, 21 Jun 2024 18:15:07 +0100
> > Ben Bacarisse <ben@bsb.me.uk> wrote:
> >  
> >> Michael S <already5chosen@yahoo.com> writes:
> >>   
> >> > On Fri, 21 Jun 2024 18:28:39 +0300
> >> > Michael S <already5chosen@yahoo.com> wrote:
> >> >    
> >> >> On Fri, 21 Jun 2024 13:58:01 -0000 (UTC)
> >> >> gazelle@shell.xmission.com (Kenny McCormack) wrote:    
> >> >> > 
> >> >> > Yeah, now I get it.  You really only need strtoimax() and
> >> >> > strtoumax().     
> >> >> 
> >> >> Which are? uunfortunately, not part of C standard.
> >> >>     
> >> >> > A result of any smaller type can be obtained by calling one of
> >> >> > these functions and storing the result in an object of the
> >> >> > smaller type.   
> >> >> 
> >> >> Or check for range and handle out of range values as
> >> >> appropriate by situation.    
> >> >
> >> > BTW, I don't know what The Standard says about out-of-range
> >> > inputs, but at least
> >> > https://en.cppreference.com/w/c/string/byte/strtol does not say
> >> > anything certain. especially about what stored in *str_end.    
> >> 
> >> It says what value should be returned.  That's something certain!
> >>  
> >
> > In case of strtol, yes. 
> > In case of strtoul it also says what value should be returned, but
> > plain reading of cppreference.com text (at least *my* plain reading)
> > does not match observed behaviour. The text on cppreference.com
> > resembles Standard text, but does not match it.  
> 
> Ah.  What's the discrepancy you see?
> 

IMHO, the Standard texts allows for more interpretations (and
misinterpretations) than cppreference.com text 


> > Also, at least to me, Standard text itself appear very far from
> > clear and way too open to interpretations.
> > My own interpretation would be that for any negative input strtoul()
> > should return ULONG_MAX and set errno to ERANGE. None of the actual
> > implementation that I tested behaves in this manner.  
> 
> I don't get that from the text.  There is, after all, no "negative
> input".  There is a "subject sequence" which, if it starts with a
> minus sign, causes the "value resulting from the conversion is
> negated (in the return type)" which seems clear enough.
>

I find it less than clear.
The most non-clear part is that for strtouxx() as long as "subject
sequence" is in range, it is first converted and then negated. However
when  "subject sequence" is out of range it is converted, then clipped
and then *not* negated.
I don't feel confused in the similar way by none-u variants of strtoxx()

> > It seems, the problem is of what is considered "range of
> > representable values" for unsigned type is by itself open to
> > interpretations.
> >
> > IMHO, even if in some part of the standard  there exists text that
> > clearly states that "range of representable values for unsigned
> > long = [-ULONG_MAX:ULONG_MAX]" it is worth repeating that in the
> > section that defines strtol, because it is at all non-intuitive.  
> 
> I don't get what you are saying here.  The range of values is
> [0:ULONG_MAX].
>

That as long as you see sign as something detached from the rest of the
number. I tend to see them as parts of the whole. May be, that's my
mistake.