Re: c++/9103: problems constructing from temporaries

["Giovanni Bajo" <giovannibajo@libero.it>]

The following reply was made to PR c++/9103; it has been noted by GNATS.

From: "Giovanni Bajo" <giovannibajo@libero.it>
To: <gcc-gnats@gcc.gnu.org>,
	<darryl.green@unitab.com.au>,
	<gcc-bugs@gcc.gnu.org>,
	<nobody@gcc.gnu.org>,
	<gcc-prs@gcc.gnu.org>
Cc:  
Subject: Re: c++/9103: problems constructing from temporaries
Date: Fri, 24 Jan 2003 17:11:38 +0100

 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&p
 r=9103
 
 Epurated test case:
 -----------------------
 struct A
 {
     A(const A& ) {}
     A(A* ) {}
     A(  ) {}
 
     void foo(void);
 };
 
 int main()
 {
      A a(A(A(new A())));
      a.foo();
 }
 -----------------------
 ice7.cpp: In function `int main()':
 ice7.cpp:116: request for member `foo' in `a()', which is of non-aggregate
 type
    `A ()()'
 
 This is on GCC 3.2. The above should clearly compile, since the line cannot
 be a function declaration (because of the 'new' in it). GCC seems to be
 confused because of the two temporaries, and you can see that also the
 dumped type is wrong. If you remove one temporary:
 
 A a(A(new A()));
 
 the code compiles correctly.  If you remove the 'new':
 
  A a(A(A(A())));
 
 the code fails as expected, but the error shows there is still some
 confusion:
 
 ice7.cpp:116: request for member `foo' in `a(A (*)(A (*)()))', which is of
    non-aggregate type `A ()(A (*)(A (*)()))'
 
 since it's missing the third function pointer (should be `A ()(A (*)(A (*)(A
 (*)())))'.
 
 For the original poster, I'd suggest using the alternative syntax A a =
 A(whatever), unless the constructors are explicit.
 
 Giovanni Bajo