Re: technology discussion → does the world need a "new" C ?

On 19/08/2024 01:01, Ben Bacarisse wrote:

Bart <bc@freeuk.com> writes:
 

You or he would have to go into more detail, such as an actual example, to
demonstrate whatever it is that you think is wrong about passing a pointer
argument by-reference.

 No one has said any such thing, so I can't see how any more detail could
help.  I suspect you've lost track of the point being made.

Probably, and perhaps not just me! But I'd still quite like to know exactly what it is that is marked as 'disallowed'.

I can't unravel this.  Take, as a concrete example, C++.  You can't pass
a pointer to function that takes an array passed by reference.  You can,
of course, pass a pointer by reference, but that is neither here nor
there.

>
OK. So why do you agree with this:
>

                            C call-by-value         call-by-reference
                            ===============         =================
        (pointer argument)  F(p)                    (disallowed)

>
What is 'pointer argument' here?

 I can't see what is confusing you about this.  I agree with the above
for exactly the reasons I wrote.

Do you mean: 'You can't pass a pointer to a function that takes an array passed by reference'?
(I assume you mean a pointer as argument to a function, rather than a 'pointer to a function'.)
I'd still need to disentangle that via a concrete example (and preferably not C++). With pass-by-reference, that is usually done on top of whatever type choices you've made. Pass-by-reference does not affect those types, but internally there may be extra indirection.
However, as I wrote a day or two ago, if attempting to retrofit pass-by-reference to C, it will interfere a little with normal array-to-pointer decay (since there will be an implicit & applied, that stops that happening).

It would be wrong (and is wrong in
C++) to pass a pointer where an array reference is expected.

Well, putting aside pass-by-reference, that would be wrong in C too, if you interpret 'array reference' to be a type like T(*)[], and a 'pointer' a type like T*.
With pass-by-reference added to C, there would be stronger type checking, so if something is disallowed, it would be for a good reason, not just because Tim said so.