31750 - Interfaces must not have virtual destructors

Status: RESOLVED INVALID

(Core :: XPCOM, defect, P3)

Description

[Heikki Toivonen (remove -bugzilla when emailing directly)]

This pops up mostly in old interfaces that were created before XPIDL was there.

Interfaces must not have virtual destructors. If this were allowed, the vtable 
would contain the destructor, so in theory you could call the C++ destructor 
from, say, JavaScript, which is wrong. I am not sure if this actually breaks 
anything (inheritance?, impossible to call destructor?), but at least it wastes 
a little space.

Comment 1

[Suresh Duddi (gone)]

Scott can you handle this.

Comment 2

[Scott Collins]

another good thing to look for with the [XP]COM lint script.

Comment 3

[Scott Collins]

mass re-assigning to my new bugzilla account

Comment 4

[Scott Collins]

Using this search

  <http://lxr.mozilla.org/seamonkey/search?string=virtual+%5C%7EnsI>

I found plenty of false hits and about 9 real cases

/intl/locale/src/windows/nsIWin32LocaleFactory.h, line 41 -- virtual 
~nsIWin32LocaleFactory(void);
/netwerk/cache/filecache/test/diskcache.cpp, line 76 -- virtual 
~nsITestDataStream() {};
/netwerk/test/TestCacheMgr.cpp, line 72 -- virtual ~nsITestDataStream() {};
/netwerk/test/TestRawCache.cpp, line 79 -- virtual ~nsITestDataStream() {};
/netwerk/test/TestWriteStream.cpp, line 45 -- virtual ~nsITestDataStream() {};
/htmlparser/src/nsIDTD.h, line 79 -- virtual ~nsIDTD() {};
/layout/html/table/src/nsITableLayoutStrategy.h, line 40 -- virtual 
~nsITableLayoutStrategy() {};
/layout/xul/base/src/nsIFrameBoxObject.cpp, line 38 -- virtual 
~nsIFrameBoxObject();
/widget/src/beos/nsWindow.h, line 248 -- virtual ~nsIWidgetStore();

Comment 5

[Thomas]

I tried the search as described in Comment #4 

I saw that /netwerk/test/TestWriteStream.cpp, line 62 -- virtual
~nsITestDataStream() {}; is still there plus some dozen other cases.

How do I know if these are false hits or real cases?