"No matching function" -- not finding copy constructor

[Joe Buck]

On Tue, May 17, 2005 at 12:00:59PM -0400, Paul Koning wrote:
> I'm upgrading to V4.0.0 and struggling with some code that's seriously
> into templates.  One puzzling error is this one:
> 
> keyed_obj.hh:159: error: no matching function for call to 'CxnIndex::CxnIndex(CxnIndex)'
> Indeces.hh:150: note: candidates are: CxnIndex::CxnIndex(CxnIndex&)
> Indeces.hh:145: note:                 ... and some more
> 
> It's not entirely clear to me why something very much like a copy
> constructor is being invoked in the first place.  But the bigger
> puzzle is: why isn't the copy constructor being matched?  I would have
> thought that any call with a T argument should match a function or
> method with an &T argument in its declaration...

CxnIndex::CxnIndex(CxnIndex&) is not a general copy constructor.  Notice
the non-const reference.  The error message is saying that it's trying
to pass a temporary to a copy constructor.  You would need

CxnIndex::CxnIndex(const CxnIndex&)

to match that.  As for why you need a copy constructor, we'd have to
see the code for that, but this list isn't really the right place for
helping you debug this problem further.