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The Law of The Big Two

36 replies on 3 pages. Most recent reply: May 9, 2008 10:32 AM by m limber

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Flat View: This topic has 36 replies on 3 pages [ « | 1 2 3 ]

Chuck Allison

Posts: 63
Nickname: cda
Registered: Feb, 2003

Re: I'm blown away

Posted: Oct 7, 2004 8:55 PM

> Providing optional GC would be a big win. Providing
> useful (and standard) counted and counting_ptr pairs
> would fix a ton of systems, but we are still fooling
> around with this?
>
> Color me disgusted.

Well, an attractive collection of smart pointers has been added to C++0x that would make you quite happy, and GC is under discussion. (Color yourself updated.) But in the meantime, we need to get by.

Steve Love

Posts: 20
Nickname: essennell
Registered: Sep, 2004

Re: I'm blown away

Posted: Oct 7, 2004 11:38 PM

> that this is still the state of discourse in C++.
>
> Frozen in time for something like 10 years.

Well folks have been working hard in that time for a "new release" of the standard, which seems likely to contain a decent - and useful - collection of pointer wrappers, including counting ones.

If the language had been moving at the rate it was pre 1997, would you have preferred it?

> Still no
> standard reference counting pointer implementation?
> Auto_ptr is weird and error prone and this level of
> f fiddling is just madness.

Ah well, auto_ptr has its uses though. Less wierd I reckon than strtok. And less error prone ;-)

> Providing optional GC would be a big win.

I'm still bemused by the amount of people who think automatic GC is some kind of silver bullet (I'm not suggesting you are one of them). I write in C# and C++ a lot, and I prefer C++'s deterministic destruction. For one thing, it makes exceptions much easier to think about.

Steve

Bronek Kozicki

Posts: 1
Nickname: brok
Registered: Oct, 2004

Re: The Law of The Big Two

Posted: Oct 19, 2004 3:03 AM

There's one misleading sentence in the article:

Another way of prohibiting copy construction and copy assignment is to make one or more members a reference or const (or const reference, for the especially cautious)this effectively shuts down the compiler's ability to generate these special member functions

As far as I remember, const or ref members won't disable copy constructor implicitly generated by compiler. It will only disable implicit copy assignment operator, or (more precisely) render program ill-formed when implicitly generated by compiler copy assignment operator is used.

alex

Posts: 2
Nickname: ipodhelp
Registered: Jan, 2005

Re: The Law of The Big Two

Posted: Jan 25, 2005 1:51 PM

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sapa

Posts: 1
Nickname: sapa
Registered: Feb, 2005

Re: The Law of The Big Two

Posted: Feb 17, 2005 7:39 AM

I realize this is a newbie question, but does this code cause a leak for the old value of p_?

Example& operator=(const Example& other) {
// Self assignment?
if (this==&other)
return *this;

*p_=*other.p_; // Uses SomeResource::operator=
return *this;
}

Marsha Pros

Posts: 1
Nickname: mkpros
Registered: Nov, 2007

Re: The Rule of The Big Two

Posted: Nov 17, 2007 3:36 PM

Iam loooking for a Dan Teske from Cleveland Ohio .1969 Grad. of Rhodes High School / St. Thomas More 1965. Please advise if you r him ...Marsha PROS Gorman

m limber

Posts: 3
Nickname: mlimber
Registered: Nov, 2006

Re: The Law of The Big Two

Posted: May 9, 2008 10:32 AM

I realize this is a newbie question, but does this code cause a leak for the old value of p_?
Example& operator=(const Example& other) { // Self assignment? if (this==&other) return *this; *p_=*other.p_; // Uses SomeResource::operator= return *this; }

With all the indirection going on, it's a bit tricky to see, but there's no leak here. The reason is that there's no memory allocation or deallocation, only copying of values. That is, the assignment statement ("*p_=*other.p_;") is copying the value of other's p_ into the location currently pointed to by this's p_. Their allocation remains the same.

A simplified example:


int *i  = new int(42);
int *i2 = new int(2008);

*i = *i2; // no leak here; just copying values

delete i2;
delete i;

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