Re: Loops (was Re: do { quit; } else { })

James Kuyper <jameskuyper@alumni.caltech.edu> writes:

On 5/13/25 22:37, Keith Thompson wrote:
>

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

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

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

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

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[...]
>

My personal interpretation is that this:
>
void func(int arr[static 5]) {
}
>
int main(void) {
    int arr[10];
    func(arr+5);    // OK
    // func(arr+6); // UB
}
>
is valid, because, for example, the last 5 elements of a 10-element
array object can be treated as a 5-element array object.  gcc seems
to agree, based on the fact that it warns about func(arr+6) but
not about func(arr+5).
>
This is a fundamental part of my mental model of C, but in a few
minutes of searching I wasn't able to find explicit wording in the
standard that supports it.

>
In N1570, 6.7.6.3 p7.

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Did you mean to imply that that paragraph supports (or refutes) my
statement?  [...]

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No.  I posted the reference to say that the cited paragraph supports
the conclusion that 'func(arr+6)' is undefined behavior.

>
...
>

To me it seems obvious that 6.7.6.3 p7 is meant to cover the
case of 'func(arr+6)' as being undefined behavior.

>
But that's not the question I was addressing.  My question is whether
func(arr+5) has defined behavior, based on whether or not a+5 points to
the *first element* of an array.

>
Tim - [...]

I don't know why you expect me to read postings meant for me but
posted as a reply to another poster.  Sometimes I do, sometimes
I don't.  You may take the correlation as being determined by
quantum mechanical uncertainty.