Re: wishlist: support for shorter pointers

[waffl3x <waffl3x@protonmail.com>]

> Hmm... that's disappointing :( nothing was generated.
Function templates are not functions, they are templates of functions, they
will not generate any code unless they are instantiated.

> then again. I've noticed that you've changed pointers to indices. 
No, I changed pointers to a template type parameter named Iter. Which is meant
to correspond to the C++ iterator interface. Pointers satisfy all of iterators
requirements, and classes that satisfy those requirements (by implementing similar semantics
to pointers) are also iterators.

> Or may be C++ does a different thing with [object++], then
> what plain-c does with [variable++]?

That's correct, C++ has operator overloading, which allows you to define
member functions for classes that are called when the corresponding operator is used.
In this case, operator++ (in the imaginary implementation) is overloaded to go to
the next element of the linked list. The iterator interface requires operator++ to
be overloaded, and should implement similar semantics to using operator++ on a
pointer.

> I's hard to analyze code without basic knowledge of the language :(

Yes, I personally recommend learncpp as a resource for learning C++, that
would aid you greatly. C++ is a large language, you would need to invest some time
into it to become proficient, in my opinion that investment is hugely worth it
though.

> I only hoped that the problem could be
> recognized and may be would inspire some developers out there

Unfortunately, I strongly agree with JWakely that what you requested belongs
in library rather than in language additions. If implementing it is too much of a
burden (which is understandable since you have no prior experience with C++) then I
would suggest checking out Boost to see if they have what you need. I seem to recall
them having some sort of fancy pointers in there somewhere. Realistically though,
it will take some time to get used to all the C++isms before you would be able to
be proficient with anything Boost would provide. I don't mean to be discouraging,
I just want to keep your expectations realistic, the learning curve for C++ can
be rather high, especially when you're used to C.

Good luck!
-Alex


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------- Original Message -------
On Wednesday, June 28th, 2023 at 6:43 AM, Rafał Pietrak <embedded@ztk-rp.eu> wrote:


> Hi Alex,
> 
> W dniu 28.06.2023 o 11:56, waffl3x pisze:
> 
> > Here's a quick and dirty example of how this function could be rewritten with
> > modern C++. I omitted some necessary details, particularly the implementation of the
> > linked list iterator. I also wrote it out quickly so I can't be certain it's 100%
> > correct, but it should give you an idea of whats possible.
> 
> 
> trying....
> 
> > // I assume you meant to return a pointer
> > template<typename Iter>
> > auto test_funct(Iter iter, Iter end, char opt) {
> > for (; iter != end; ++iter) {
> > // dereferencing iter would get buff
> > if (!*iter) { *iter = opt; break; }
> > }
> > return iter;
> > }
> 
> -------------------------- TEST.CPP is the above code
> $ g++ -fpermissive -c test.cpp
> 
> > > no error, GOOD :)
> 
> $ g++ -fpermissive -S test.cpp
> $ cat test.s
> .file "test.cpp"
> .text
> .ident "GCC: (Debian 12.2.0-14) 12.2.0"
> .section .note.GNU-stack,"",@progbits
> ---------------end-of-file----------
> 
> Hmm... that's disappointing :( nothing was generated.
> 
> then again. I've noticed that you've changed pointers to indices. I've
> pondered that for my implementation too but discarded the idea for it
> will require adjustments by struct-size (array element size) on every
> access.... Or may be C++ does a different thing with [object++], then
> what plain-c does with [variable++]?
> 
> I's hard to analyze code without basic knowledge of the language :(
> 
> > I also made an example using the C++ algorithms library.
> > 
> > template<typename Iter>
> > auto test_funct(Iter begin, Iter end, char opt) {
> > auto iter = std::find_if(begin, end, [](auto buff){return !buff;});
> > if (iter) {
> > *iter = opt;
> > }
> > return iter;
> > }
> 
> 
> here I got:
> test2.cpp:3:22: error: ‘find_if’ is not a member of ‘std’
> so, it's a nogo for me either.
> 
> > As I said, there's quite a bit omitted here, to be blunt, implementing both
> > the fancy pointers (especially when I don't know anything about the hardware) and
> > the iterators required would be more of a task than I am willing to do. I'm happy
> > to help but I don't think I should be doing unpaid labor :).
> 
> 
> Fair enough.
> 
> [---------]
> 
> > I'm happy to answer more questions and help, however I'm concerned this is
> > getting fairly unrelated to GCC.
> 
> 
> From my perspective it is related to GCC (well... ok, to CC in general
> - it "smells" like an extention to "C-standard" providing additional
> "funny" semantics to CC. But GCC is a "front-runner" for CC evolution,
> right? :).
> 
> Then again. I'm not into drawing anybody into unfruitful and pointless
> support (for my little project). I only hoped that the problem could be
> recognized and may be would inspire some developers out there (as it
> would be silly for me, if I thought its implementation into GCC could
> happen before my small project ends, right?).
> 
> Anyway, thanx for the hints and suggestions.
> 
> -R