971127 array initialization problem!?!

971127 array initialization problem!?!

[neal]

This trivial test program seems to show a serious problem with array
initialization in g++ egcs-971127 (or has something changed in recent
c++ that I'm not aware of?)

struct QBitmap {
  QBitmap (int,int, bool=false);
};
  
main () {
  QBitmap* x = new QBitmap(2,2);
  QBitmap* y = new QBitmap[5](2,2);
}
g++ -c Test.c
Test.c: In function `int main()':
Test.c:9: no matching function for call to `QBitmap::QBitmap (int)'
Test.c:5: candidates are: QBitmap::QBitmap(const QBitmap &)
Test.c:4:                 QBitmap::QBitmap(int, int, bool)

Re: 971127 array initialization problem!?!

[Alexandre Oliva]

  writes:

> This trivial test program seems to show a serious problem with array
> initialization in g++ egcs-971127 (or has something changed in recent
> c++ that I'm not aware of?)

C++ has never allowed initialization of dynamically constructed arrays
with non-default constructors.  The error message is misleading.

-- 
Alexandre Oliva
mailto:oliva@dcc.unicamp.br mailto:aoliva@acm.org
http://www.dcc.unicamp.br/~oliva
Universidade Estadual de Campinas, SP, Brasil

Re: 971127 array initialization problem!?!

[Lassi A. Tuura]

neal@ctd.comsat.com wrote:
>   QBitmap* y = new QBitmap[5](2,2);

This is not valid C++ syntax -- initialisers are not allowed in
array-new expression.  Code like this used to compile with g++, but I
don't know if it ever was officially supported GNU extension.  If the
feature has been removed, the diagnostic could be improved...

Cheers,
//lat
-- 
Lassi.Tuura@cern.ch          There's no sunrise without a night

Re: 971127 array initialization problem!?!

[Robert Wilhelm]

On Mon, Dec 01, 1997 at 08:52:19AM +0100, Lassi A. Tuura wrote:
> neal@ctd.comsat.com wrote:
> >   QBitmap* y = new QBitmap[5](2,2);
> 
> This is not valid C++ syntax -- initialisers are not allowed in
> array-new expression.  Code like this used to compile with g++, but I
> don't know if it ever was officially supported GNU extension.  If the
> feature has been removed, the diagnostic could be improved...
>

Would the g++ maintainers accept patches to restore the old behavior?

I have quite a lot of code which depends on 
this unofficial behavior :-(

Re: 971127 array initialization problem!?!

[Joe Buck]

> On Mon, Dec 01, 1997 at 08:52:19AM +0100, Lassi A. Tuura wrote:
> > neal@ctd.comsat.com wrote:
> > >   QBitmap* y = new QBitmap[5](2,2);
> > 
> > This is not valid C++ syntax -- initialisers are not allowed in
> > array-new expression.  Code like this used to compile with g++, but I
> > don't know if it ever was officially supported GNU extension.  If the
> > feature has been removed, the diagnostic could be improved...
> >
> 
> Would the g++ maintainers accept patches to restore the old behavior?
> 
> I have quite a lot of code which depends on 
> this unofficial behavior :-(

I would advise against it.  g++ can't carry baggage forever.  I'd like
for us to encourage people to write C++ and do a good job compiling it,
rather than encourage them to write a different language called "g++".

As for your "quite a lot of code", use vectors to get the same effect:

	vector<QBitmap> y(5, QBitmap(2,2));

If you must have C arrays, you could use placement new to do the
construction.