In article <3173B383.41C67EA6@rstcorp.com> "Aaron S. Binns"
<asbinn@rstcorp.com> writes:

|> [Moderator's note: This is crossposted to comp.std.c++ and
|> comp.lang.c++, and followups have been set to comp.std.c++. mha]

|> I recently came across a piece of code that reads:

|> class A {
|>   // contents of class A
|> } a1, *a2, const *a3;

While I personally wouldn't write anything like this, it is definitly
legal.

|> This looks pretty bogus to me.  I thought that the 'const' applied
|> to the elaborated specifier 'class A'.  If the 'const' qualifier is
|> supposed to apply to the pointer in 'a3', then it should come _after_
|> the '*'.

No, it is the A being pointed to that is const, not the pointer.

Separating each of the definitions out into a separate statement makes
this obvious:

    class A { ... } ;
    A               a1 ;
    A*              a2 ;
    A const*        a3 ;

|> I think that either one of the two following was intended.

|> 1)

|> class A {
|>   // contents of class A
|> } a1, *a2, * const a3;


|> 2)

|> class A {
|>   // contents of class A
|> } a1, *a2;

|> A const *a3;  // Or const A *a3;

Regardless of what was intended, 2 is the interpretation required by
the draft standard (and by the C standard).
--
James Kanze         Tel.: (+33) 88 14 49 00        email: kanze@gabi-soft.fr
GABI Software, Sarl., 8 rue des Francs-Bourgeois, F-67000 Strasbourg, France
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In article <KANZE.96Apr17121453@slsvgqt.lts.sel.alcatel.de> kanze@lts.sel.alcatel.de (James Kanze US/ESC 60/3/141 #40763) writes:
>In article <3173B383.41C67EA6@rstcorp.com> "Aaron S. Binns"
><asbinn@rstcorp.com> writes:
>|> I recently came across a piece of code that reads:
>
>|> class A {
>|>   // contents of class A
>|> } a1, *a2, const *a3;
>
>While I personally wouldn't write anything like this, it is definitly
>legal.

No, I'm sorry, that's not true.  This little syntactic oddity is something
accepted by the Microsoft compiler, but it's not standard C or C++.
The part that gets repeated in a declaration comma list is the declarator,
and the cv-qualifiers can only appear following a pointer or pointer-to-member
declarator in the declarator syntax.

A little research with the Microsoft compiler suggests that:

  int i, const j, const *k;  // Declares j as "const int", k as "int *"

So the "const" above does nothing.  But that is outside the scope of
comp.std.c++.

Steve Adamczyk
Edison Design Group
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In article <KANZE.96Apr17121453@slsvgqt.lts.sel.alcatel.de>
kanze@lts.sel.alcatel.de (James Kanze US/ESC 60/3/141 #40763) writes:

|> In article <3173B383.41C67EA6@rstcorp.com> "Aaron S. Binns"
|> <asbinn@rstcorp.com> writes:

|> |> [Moderator's note: This is crossposted to comp.std.c++ and
|> |> comp.lang.c++, and followups have been set to comp.std.c++. mha]

|> |> I recently came across a piece of code that reads:

|> |> class A {
|> |>   // contents of class A
|> |> } a1, *a2, const *a3;

|> While I personally wouldn't write anything like this, it is definitly
|> legal.

Actually, on further thought, I don't think it is legal.  In the statement:

 A const*  a3 ;

The const is part of the `declaration-specifiers', and not the
`declarator'.  When multiple symbols are declared in the same line, as
here, the list contains declarators, and cannot contain additional parts
of the declaration-specifiers.

A quick check of the grammar shows that the first token of a declarator
must be one of { `*', `(' , <identifier> }.  The keyword `const' is none
of these.
--
James Kanze           (+33) 88 14 49 00          email: kanze@gabi-soft.fr
GABI Software, Sarl., 8 rue des Francs Bourgeois, 67000 Strasbourg, France
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[Moderator's note: This is crossposted to comp.std.c++ and
comp.lang.c++, and followups have been set to comp.std.c++. mha]

I recently came across a piece of code that reads:

class A {
  // contents of class A
} a1, *a2, const *a3;


This looks pretty bogus to me.  I thought that the 'const' applied
to the elaborated specifier 'class A'.  If the 'const' qualifier is
supposed to apply to the pointer in 'a3', then it should come _after_
the '*'.

I think that either one of the two following was intended.

1)

class A {
  // contents of class A
} a1, *a2, * const a3;


2)

class A {
  // contents of class A
} a1, *a2;

A const *a3;  // Or const A *a3;


Is my interpretation of the binding of 'const' more or less correct?

BTW, this code _is_ accepted by the Microsoft VC/C++ v2.0 compiler.


--
 Aaron S. Binns                   Reliable Software Technologies Corp.
                                  21515 Ridgetop Circle, Suite 250
 asbinn@rstcorp.com               Sterling, VA 20166
     http://www.rstcorp.com
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