[setup] Why does PackageSpecification have a privatecopy-constructor? (Robert?)

[Max Bowsher]

Robert Collins wrote:
> On Mon, 2004-08-30 at 18:33 +0100, Max Bowsher wrote:
>> I can't see why setup's PackageSpecification class has a private
>> copy-constructor.
>> Am I missing something?
>
> erm. to only allow the class itself to create copies.

Yes, but why was it decided to make that restriction? Either I am missing 
something, or it is a pointless restriction.

>> The reason why I am suddenly interested is that the C++ standard says 
>> that
>> this:
>>
>> foo(SomeClass())
>>
>> requires SomeClass's copy-constructor to be accessible (bizarre, no?) and
>> g++ 3.4 has decided to enforce this.
>
> Even if that is in a method:
> SomeClass *
> SomeClass::funkyCopy() const
> {
>   SomeClass *result(self);
> }
> ?

Well, obviously in a method of SomeClass, private things of SomeClass are 
accessible.
I wasn't able to convert what you mentioned above into a compilable example 
(attached is my errorring attempt) - but even if I was, it's a bit deviously 
mysterious, and may be entirely unneeded if we can make the copy-constructor 
public.

>> So, unless I can make the
>> copy-constructor public (which I don't want to do if doing so risks other
>> problems), I need to rewrite all code like:
>>
>> do_something(PackageSpecification(somename))
>>
>> to:
>>
>> PackageSpecification tmppkgspec(somename);
>> do_something(tmppkgspec);
>>
>> which isn't very nice.
>
> So we have code like that at the moment?

Certainly. 4 occurrences in IniDBBuilderPackage.cc and 1 in package_db.cc.

Max.

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