Re: The difference between strtol() and strtoul() ?

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

Tim Rentsch <tr.17687@z991.linuxsc.com> writes:

Ben Bacarisse <ben@bsb.me.uk> writes:
[range questions for strtol(), etc]
>

I think there /is/ something problematic with the wording about the
negation.  It happens "in the return type" but how can
9223372036854775808 be negated in the type long long int?  OK, the
negated value can be /represented/ in the type long long int but that's
not quite the same thing.  On the othee hand, for the unsigned return
types, the negation "in the return type" is what produces ULONG_MAX for
"-1" when the negated value, -1, can't be /represented/ in the return
type.  It's a case where, over the years, I've just got used to what's
happening.

>
I understand what these functions do, but their specification in the
C standard is a little off.  To my way of thinking the impact is
minimal, but the specified behavior is either unequivocally wrong or
there are some cases that give rise to undefined behavior.

>
Can you give an example where the specified behavior causes undefined
behavior?

I don't want to pre-empt Tim's answer, but the wording that bothers me
is

  "If the subject sequence begins with a minus sign, the value resulting
  from the conversion is negated (in the return type)."

For strtoll("-9223372036854775808", 0, 0) the value resulting from the
conversion is 9223372036854775808 which can not even be represented in
the return type, so how can it be negated "in the return type"?

--
Ben.