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new/delete in ctor/dtor

MichaelBartman · 2003-08-13T06:17:03

Hey, I have two classes similar to the two examples below. class b { }; class a { b *temp; a *next, *prev; public: a() { next = 0; prev = 0; temp = new b(); } ~a() { delete temp; } }; When I make an instance of class a, and then delete it it will crash with an exception error in Release mode. But in debug mode, it runs flawlessly as far as I can tell. If I take out b *temp and delete temp from the ctor/dtor then it does not crash. I thought that maybe it was because b was an empty class(it''s a dummy class that I haven''t filled in yet), but even if I fill in b with member variables and methods it still crashes. Any suggestions would be warmly welcomed. Thanks, Michael Bartman

General and Gameplay Programming Programming

Started by MichaelBartman August 10, 2003 03:07 PM

16 comments, last by MichaelBartman 20 years, 8 months ago

MichaelBartman

122

Author

August 10, 2003 07:32 PM

Thanks for all of your help guys,

I had tried doing temp = new b; but that it still had the same problem. That''s when I tried filling in a ctor and dtor for class b, btu that still didn''t work.

Deep copy just sounds more confusing than it really is

. I had a quick look in my copy of C++ Primer 2nd Edition, but there wasn''t anything about it so I figured it was something complex :|

Thanks again for all of the help!

Michael BartmanCEO, Lead ProgrammerDark Omen Studios

fallenang3l

144

August 10, 2003 10:39 PM

In class a, define this:

a(const a&){    temp = new b;}a& operator =(const a& rhs){    if (this == &rhs) // not really necessary in this example, but it''s a good habit to always check for self-assignment        return *this;    delete temp;    temp = new b;    return *this;}

Sneftel

1,788

August 10, 2003 10:55 PM

fallenang3l''s code also pointed out something else to watch for: If you''re implementing a copy constructor, you''ll also want to implement an assignment operator, because that''s another source of initialization/finalization. It''s the Rule of Three (which I seem to be quoting almost daily these days): If your class specifies a destructor, an assignment operator, or a copy constructor, it will most likely need all three.

How appropriate. You fight like a cow.

Lektrix

106

August 11, 2003 07:23 AM

Is everyone blind? Did I not do that in my post? Indeed.

[ Google || Start Here || ACCU || STL || Boost || MSDN || GotW || MSVC++ Library Fixes || BarrysWorld || E-Mail Me ]

[ Google || Start Here || ACCU || STL || Boost || MSDN || GotW || CUJ || MSVC++ Library Fixes || BarrysWorld || [email=lektrix@barrysworld.com]E-Mail Me[/email] ]

JohnBolton

1,373

August 11, 2003 12:32 PM

MichaelBartman: There is absolutely nothing wrong with the code you posted. The problem must be in the code you omitted or somewhere else.

John BoltonLocomotive Games (THQ)Current Project: Destroy All Humans (Wii). IN STORES NOW!

MichaelBartman

122

Author

August 11, 2003 04:46 PM

I don''t know how it could be any code that I omitted, because there is only a problem when I do a new on an object of type b, and then delete it. I don''t do anything to it besides that, and when I comment out the line with the new and the line with the delete everything works fine and dandy.

Maybe Visual Studio is just telling me I should have stuck with 6 and not gone to .NET? lol

Michael BartmanCEO, Lead ProgrammerDark Omen Studios

mfawcett

374

August 13, 2003 02:47 AM

quote:Original post by MichaelBartman
Maybe Visual Studio is just telling me I should have stuck with 6 and not gone to .NET? lol

...hardly. Implement what the other posters have already mentioned and you should be fine. If defining a proper copy ctor, dtor, and assignment operator doesn''t fix the problem, then your problem lies elsewhere.

--Michael Fawcett

flangazor

516

August 13, 2003 06:17 AM

quote:Original post by C-Junkie
quote:Original post by dmounty
why would this only happen with a release compile, and not with a debug compile?

Because the release compile optimizes something which exposes the bug in a way where its not just an unchecked error code someplace, but a crash bug...

Never happened to you before? Lucky you...

Its happened to me and the ensuing language spewing from my mouth made the wallpaper peel.

new/delete in ctor/dtor

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