Virtual?

John Dowis · 2003-01-23T20:30:57

First of all, since this is my first post here I want to say thanks to the people who run this site. I am a senior CS major, and I''ve been wondering when I was going to learn the REAL stuff. Good thing I happened to come here. I read the reviews on Andre LaMothe''s "Tricks of the Windows Game Programming Gurus", and on their advice I decided to buy it... in three days I have learned more on programing than the last three years of college. In particular, his explanation of Windows32 programming helped me greatly, as I knew nothing about it from school. However, I had a question on something I am reading that I don''t understand. He uses a lot of C, whereas I am entirely trained (in the order I learned them) in Basic, Pascal, C++, Ada, VC++. I don''t know a lot of the old C stlye commands, so I guess it is making it hard to understand some of LaMothe''s code (although, as the people here said, he is very good at explaining his code). One part I don''t understand is: virtual void _stdcall fx(void) = 0; The main problems I am having with this are the parts "virtual", "_stdcall", and I am also wondering why he put "void" as a parameter to the function "fx" (at least it appears that way), and then why (or how he even can) set it equal to anything, in this case 0. Thanks in advance for any help, I greatly appreciate it. -John Dowis

For Beginners

Started by John Dowis January 19, 2003 05:42 PM

56 comments, last by John Dowis 21 years, 3 months ago

sark

104

January 22, 2003 11:12 AM

quote:Original post by ph33r
I realized I was wrong, Sark made the comment that 3 people disagree with me so I better give up. I was not trying to debate the standard I was meerly addressing the issue that people shouldn''t give up in an arguement because of the numbers on one''s oppenents size.

It wasn''t meant seriously, hence the "

". Christ.

NotAnAnonymousPoster

286

January 22, 2003 11:38 AM

quote:Original post by SabreMan
I''ve earned a reasonable amount of money from knowing stupid stuff about it. Does that count?

I suppose it does.

quote:
Because you believe that C++ is an inferior programming language.

quote:Original post by SabreMan
Right, but I didn''t used to think that, so something caused a change.

Don''t worry, I trust what you''re saying. If I didn''t I wouldn''t bother asking you questions. All the arguments you''ve made against C++ which I have read have been very well substantiated. And it''s left me all the more eager to start messing around with Smalltalk.

"C combines all the power of assembly language with all the ease of use of assembly language"

ph33r

380

January 22, 2003 01:54 PM

I''m going back to my originial stance that you do not need to declare the base classes dtor virtual even when you call delete on it.

I did some research(with my friend''s insperation) and I found this quote in Bjarne Stroustrup''s book "The C++ Programming Language Special Edition"

quote:
page 423 Section 15.6
In other words, if you want to supply an allocator/deallocator pair that works correctly for derived classes, you must either supply a virtual destructor in the base class or refrain from using the size_t arguement in the deallocator. Naturally, the language could have been designed to save you from such concerns. Howeever, that can be done only by also "saving" you from the benefits of the optimizations possible in the less safe system.

What Stroustrup is saying is that you do not have to declare the base virtual and he left it out for people who know how to manage their memory properly and no how to deallocate memory. As Sabreman so elequently said

quote:
Sabreman
"Usually because defining the behaviour would force some implementations to utilise inefficient mechanisms for realising the behaviour. C++ sacrifices all manner of sanity at the altar of performance."

The C++ language was built to be high performance and it was built to allow you to manage your own memory that is why you have the option of declaring your base dtor to be virtual or not.

error 500

SabreMan

504

January 23, 2003 05:17 AM

quote:Original post by ph33r
In other words, if you want to supply an allocator/deallocator pair that works correctly for derived classes, you must either supply a virtual destructor in the base class or refrain from using the size_t arguement in the deallocator.

This has nothing to do with your original claim, which is still wrong.

[edited by - SabreMan on January 23, 2003 6:19:44 AM]

ph33r

380

January 23, 2003 10:44 AM

He specifically says that you can use virtual dtor''s or you can refrain from using it. I''m assumming you have that book read that section.

Anonymous

January 23, 2003 03:17 PM

!Nike - Just don''t do it...

SabreMan

504

January 23, 2003 04:26 PM

quote:Original post by ph33r
He specifically says that you can use virtual dtor''s or you can refrain from using it.[...]

If you implement your own memory management scheme which takes care of the gory details.

ph33r

380

January 23, 2003 08:30 PM

Exactly sabreman

So you don''t have to have a virtual dtor if you manage your own memory which I said way back on page 2.

500x3

Virtual?

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