Re: passing ref to ptr again as ref to ptr....

From:
James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Tue, 29 Apr 2008 01:09:15 -0700 (PDT)
Message-ID:
<0d4e8f0c-6afc-449d-8841-60e000a4a0ec@59g2000hsb.googlegroups.com>
On Apr 28, 12:17 pm, gpderetta <gpdere...@gmail.com> wrote:

On Apr 28, 11:12 am, James Kanze <james.ka...@gmail.com> wrote:

On Apr 24, 11:53 pm, "Bo Persson" <b...@gmb.dk> wrote:

osama...@gmail.com wrote:


    [...]

Does that mean references and templates are not to be mixed?

No, they work very well together. I think the void* is the
problem here, and that you are trying too hard to optimize the
code.
I would trust my compiler here, and just write
template<class T>
class GenericQueue
{
    bool Pop(T&);
};


Given that he requires pointer semantics, and copying a pointer
cannot throw, there's no reason not to just use
    T* pop() ;
in the generic interface.

if that is the interface needed (it probably is not - take a
look at std::queue and std::stack).


There's a slight difference. The standard containers are
designed to store values, not (only) pointers. So the
alternatives are:

 -- return a T, but not be thread safe,

[...]
Globally, I think the first alternative was dismissed because of
the lack of thread safety (although I think it was what was used
in the original STL); of the latter two, the last seems to offer
the most flexibility, and was chosen.


IIRC, it had more to do with exception safety: if the copy
constructor throws an exception when returning the pop'd
object, you will lose the object with no way to recover it (it
has already been removed from the internal queue). There is
no such a problem with the separated 'T&top()' and 'void
pop()'


Yes. I don't know why I wrote thread---the issue was definitely
exceptions, and the impossibility to offer a strong guarantee.

--
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