Pointers and polymorphism explained [preview, PDF, part of my attempted "Correct C++ Tutorial"]

[Alf P. Steinbach]

So, I got the itch to write something more...

I apologize for not doing more on the attempted "Correct C++ Tutorial"
earlier, but there were reasons.

This is an UNFINISHED and RAW document, and at the end there is even pure
mindstorming text left in, but already I think it can be very useful.

<url: http://home.no.net/dubjai/win32cpptut/special/pointers/preview/pointers_01__alpha.doc.pdf>.
What do you think?

In particular, if you find any grave errors, please do not hesitate to
comment. I always make errors. Those I agree are errors will be corrected.
Contents (so far):

1 1 Pointers.
1 1.1 Introduction to the basics.
1 1.1.1 How to obtain a pointer to a given object, and how to use that pointer.
3 1.1.2 The nullpointer value, valid and invalid pointers.
6 1.1.3 How to implement out-arguments by using pointers.
8 1.1.4 How to implement in-arguments by using pointers.
9 1.1.5 How to use C++ style references instead of C style pointers for arguments.
11 1.1.6 How to access main arguments.
12 1.1.7 Const-correctness for pointers (and references).
14 1.2 Run-time polymorphism.
14 1.2.1 Polymorphism.
16 1.2.2 The concept of linked data structures.
17 1.2.3 C-style polymorphism with simulated dynamic types (just one actual type).
19 1.2.4 Basic use of dynamic memory allocation & deallocation.
22 1.2.5 How to use function pointers to simulate dynamic types, C-style.
25 1.2.6 Using real types and inheritance for logical sub-types, mostly C-style.
32 1.2.7 Using vtables, mostly C-style (also a few words about abstract classes, etc.).
38 1.2.8 C++ virtual member functions.
45 1.2.9 C++ destructors and polymorphic delete.
49 1.2.10 Object ownership and the C++ std::auto_ptr.
53 1.2.11 C++ constructors and exception safety for new.
57 1.3 Dynamically allocated objects versus others.
58 1.3.1 Ensure dynamic allocation using C++ access specifiers and copy constructors.
61 – End Of Text –

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

[Alf P. Steinbach]

Again I ask for comments, corrections, praise, damnations, nits, etc.!

Of the new stuff added since the alpha3 version I think most interesting
is perhaps the section on how to ensure that smart pointers are used.

By discussing that I'm taking a leap, for as far as I know the technique
hasn't been used in production (I've never seen it discussed or used),
so comments about this would especially appreciated. E.g., are there
problems using that with Loki's small object allocator? I don't know,
but I think it appears to be so useful that it deserves discussion, even
if it turns out there are restrictions for very special usage contexts.
PDF document:
<url:
http://home.no.net/dubjai/win32cpptut/special/pointers/preview/pointers_01_beta.doc.pdf>

Examples source code:
<url:
http://home.no.net/dubjai/win32cpptut/special/pointers/preview/examples.zip>

Contents:
Please see the PDF document's table of contents.

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

[Vince Morgan]

"Alf P. Steinbach" <al***@start.no> wrote in message
news:43****************@news.individual.net...

Again I ask for comments, corrections, praise, damnations, nits, etc.!

Of the new stuff added since the alpha3 version I think most interesting
is perhaps the section on how to ensure that smart pointers are used.

By discussing that I'm taking a leap, for as far as I know the technique
hasn't been used in production (I've never seen it discussed or used),
so comments about this would especially appreciated. E.g., are there
problems using that with Loki's small object allocator? I don't know,
but I think it appears to be so useful that it deserves discussion, even
if it turns out there are restrictions for very special usage contexts.
PDF document:
<url:
http://home.no.net/dubjai/win32cpptut/special/pointers/preview/pointers_01_beta.doc.pdf>
Examples source code:
<url:
http://home.no.net/dubjai/win32cpptut/special/pointers/preview/examples.zip>
Contents:
Please see the PDF document's table of contents.

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q:

I think you have done an excellent job from what I have read so far Alf.
I've a way to go to finish chapter one, but I like the style of this very
much.
Not too verbose, but certainly not lacking in substance either.
The © won't do you any good in this case. I'm keeping it!

--
Vince Morgan
Remove UNSPAM
vi****@UNSPAMoptusnet.com.auWhat is the most annoying thing on usenet and in
e-mail?

[Vince Morgan]

"Alf P. Steinbach" <al***@start.no> wrote in message
news:43****************@news.individual.net...

Again I ask for comments, corrections, praise, damnations, nits, etc.!

Of the new stuff added since the alpha3 version I think most interesting
is perhaps the section on how to ensure that smart pointers are used.

By discussing that I'm taking a leap, for as far as I know the technique
hasn't been used in production (I've never seen it discussed or used),
so comments about this would especially appreciated. E.g., are there
problems using that with Loki's small object allocator? I don't know,
but I think it appears to be so useful that it deserves discussion, even
if it turns out there are restrictions for very special usage contexts.
PDF document:
<url:
http://home.no.net/dubjai/win32cpptut/special/pointers/preview/pointers_01_beta.doc.pdf> The section: Obtaining a pointer to(also called address of) a given object.
Half way through second paragraph.
<quote>
"However, with the C++98 standard it's not always formally the case that &*p
is

identically the same as writing just p, because the address might not permit
dereferencing. And

when p is a variable, as above, p is an lvalue that can be assigned to,
whereas &*p yields an rvalue."

</quote>

Did you mean *&p as opposed to "&*p"?
Examples source code:
<url:
http://home.no.net/dubjai/win32cpptut/special/pointers/preview/examples.zip>
Contents:
Please see the PDF document's table of contents.

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

Vince Morgan
Remove UNSPAM
vi****@UNSPAMoptusnet.com.au

[Alf P. Steinbach]

* Vince Morgan:

PDF document:
<url:
http://home.no.net/dubjai/win32cpptut/special/pointers/preview/pointers_01_beta.doc.pdf>

The section: Obtaining a pointer to(also called address of) a given object.
Half way through second paragraph.
<quote>
"However, with the C++98 standard it's not always formally the case
that &*p is identically the same as writing just p, because the address
might not permit dereferencing. And when p is a variable, as above, p is
an lvalue that can be assigned to, whereas &*p yields an rvalue."
</quote>

Did you mean *&p as opposed to "&*p"?

No.

First case. p is a pointer. If the pointer value permits dereferencing
(e.g., is not a nullpointer), then *p gives you what p points to. &*p
then gives you the address of that object, i.e. the same value as p, but
only if the pointer value permits dereferencing.

Second case. *p is an lvalue, an object that (apart from constness) can
appear as the Left hand side of an assignment. &*p is an rvalue.

Hth.,

- Alf

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?