Re: CMAP under vs2005+

From:
"Martin T." <0xCDCDCDCD@gmx.at>
Newsgroups:
microsoft.public.vc.language
Date:
Wed, 29 Oct 2008 13:12:34 +0100
Message-ID:
<ge9jvj$3vo$1@registered.motzarella.org>
Tommy wrote:

Martin T. wrote:

Note that std::map (as all std containers) does not have a virtual
destructor. (As opposed to CMap that is inheriting from CObject which
has a virt dtor).

 >

So you should never use your CMapEx polymorphically!


Hi Martin,

I think I understand what you mean by this, but I am not sure.

Is this something the compiler will highlight? will it compile if I
tried use CMapEx polymorphically?

I'm an engineer, not a CS major so I learn by best by example :-)

Can you provide an practical example of what you mean by this? How
CMapEX should not be used?

I have it now as such:

  class CMapEx : public std::map<TKEYSTR, VALUE, __cbCStringCaseCmp>
  {
  ...
  }

I believe this considered a polymorph of the std::map class. Is this
correct?


Read: [20.7] When should my destructor be virtual?
http://www.parashift.com/c++-faq-lite/virtual-functions.html#faq-20.7

That means that you should never do:
[pseudocode]
CMapEx* pmex = new CMapEx;
std::map* pm = pmex;
....
delete pm; .. The dtor of CMapEx wont be called.
[/pseudocode]
Which you probably won't do anyway.

br,
Martin

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