NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/std/c++/647

Text File | 1996-08-06 | 2.5 KB | 76 lines

Path: chronicle.mti.sgi.com!austern
From: James Kanze US/ESC 60/3/141 #40763 <[e-mail]>
Newsgroups: comp.std.c++
Subject: Re: Inialization and user-defined conversion
Date: 06 Mar 1996 10:06:23 PST
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X-Original-Date: Wed, 6 Mar 96 19:03:55 +0100
In-Reply-To: Alexander Krotoff's message of 05 Mar 1996 09:45:02 PST
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In article <[e-mail]> Alexander Krotoff
<[e-mail]> writes:

|> I have a confusion with initialization of class objects.
|> Example:

|> class C {
|>  public:
|>     C(int i);
|> };

|> class D {
|>  public:
|>     D(C c);
|> };

|> D d = 1;

|> void f()
|> {
|>     D d = 1;
|> }

|> I assume, that both initializations are wrong, since they require sequence
|> of two user-defined conversions. But some compilers disaggre ;-)

Correct.  This is a difference in the initialization formats: if you
had written `D d( 1 )', they would be legal.  Apparently, some
compilers are not making the distinction.  (The compiler is allowed to
optimize out the temporary and the call to the copy constructor, but
this is just an optimization, and is not allowed to affect the
legality of the program.)

|> Boralnd c++ 4.0:    cannot convert "int" to "D"
|> g++ 2.7.2:        no matching funcion for call to "D::D(int)"
|> MS VC 4.0:        no errors
|> Watcom 10.0:        no errors

|> As seems to me only Borland gives adequate diagnostics.

|> Who is right ?

Borland and g++.  While I find the g++ diagnostics acceptable, it's
true that the Borland one is clearer, particularly for a neophyte.

--
James Kanze         Tel.: [phone]        email: [e-mail]
GABI Software, Sarl., 8 rue des Francs-Bourgeois, F-67000 Strasbourg, France
Conseils, Θtudes et rΘalisations en logiciel orientΘ objet --
                -- A la recherche d'une activitΘ dans une region francophone
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