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

On 10/07/2024 00:35, Ben Bacarisse wrote:

bart <bc@freeuk.com> writes:
 

On 09/07/2024 18:22, Ben Bacarisse wrote:

bart <bc@freeuk.com> writes:
>

On 09/07/2024 16:58, Ben Bacarisse wrote:

bart <bc@freeuk.com> writes:
>

Arrays are passed by reference:
>
     void F(int a[20]) {}
>
     int main(void) {
       int x[20];
       F(x);
     }

This is the sort of thing that bad tutors say to students so that they
never learn C properly.  All parameter passing in C is by value.  All of
it.  You just have to know (a) what the syntax means and (b) what values
get passed.

>
The end result is that a parameter declared with value-array syntax is
passed using a reference rather than by value.
>
And it does so because the language says, not because the ABI requires
it. A 2-byte array is also passed by reference.

An address value is passed by value.  C has only one parameter passing
mechanism.  You can spin it as much as you like, but C's parameter
passing is simple to understand, provided learner tune out voices like
yours.

>
Little about C's type system is simple.

 Parameter passing is relatively simple though since there is only one
mechanism -- pass by value.

Except when it comes to arrays. Obviously arrays aren't passed by value, but that's because of X and Y.
What would be genuinely simple is:
    void F(T x) {}
    void G(T* y) {}
where an object of type T is always passed by value, and that of type T* always passes a pointer to the value. Here, T represents exactly the same type as when it used outside a parameter list:
    T a;
    T* p;
but only in the context of C is it necessary to mention that, since it C, that may not be the case.
(The mechanisms of the underlying ABI do not affect this; they just make implementation harder.)

You're doing your students a
disservice if you try and hide all the quirks.

 If.  Always with the if.  There are lots of things I don't do that would
be doing my students a disservice were I to do them.  Beautiful spin!

Have a look at forums like the Reddit one on C programming, to see the kinds of things that people learning C get confused about. Lots of them are to do with the funny quirks of C, and a big proportion are due to how arrays and pointers are so intertwined in that language.
Well, C can't be fixed. But what would you do: explain the flaws in the language, the discontinuities, or brush them under the carpet?
Or maybe explain the quirks, but pretend they are by design?
What I find especially wonderful is that every time you see a pointer type like T*, C gives you an extra array dimension on top, whether or not T actually points to the first element of an array.
So you never know whether T* is intended to represent a 0- or 1-dimensioned object, or a 1- or 2-dimensioned one.
And what I find frustrating is that people learning C get the idea that all this quirkiness goes hand-in-hand with lower-level programming.