808146 - nsProxyRelease.h:156:356: warning: deleting object of polymorphic class type ‘nsMainThreadPtrHolder<nsIUrlClassifierLookupCallback>’ which has non-virtual destructor might cause undefined behaviour [-Wdelete-non-virtual-dtor]

Status: RESOLVED FIXED

(Core :: XPCOM, defect)

Description

[Daniel Holbert [:dholbert]]

Just noticed this mess of warning-spam, when building in url-classifier:
{
nsUrlClassifierDBService.cpp
In file included from /scratch/work/builds/mozilla-central/mozilla-central.10-12-09.12-05/mozilla/toolkit/components/url-classifier/nsUrlClassifierProxies.h:10:0,
                 from /scratch/work/builds/mozilla-central/mozilla-central.10-12-09.12-05/mozilla/toolkit/components/url-classifier/nsUrlClassifierDBService.cpp:23:
../../../dist/include/nsProxyRelease.h: In instantiation of ‘nsrefcnt nsMainThreadPtrHolder<T>::Release() [with T = nsIUrlClassifierLookupCallback; nsrefcnt = unsigned int]’:
../../../dist/include/nsAutoPtr.h:874:13:   required from ‘nsRefPtr<T>::~nsRefPtr() [with T = nsMainThreadPtrHolder<nsIUrlClassifierLookupCallback>]’
../../../dist/include/nsProxyRelease.h:159:7:   required from here
../../../dist/include/nsProxyRelease.h:156:356: warning: deleting object of polymorphic class type ‘nsMainThreadPtrHolder<nsIUrlClassifierLookupCallback>’ which has non-virtual destructor might cause undefined behaviour [-Wdelete-non-virtual-dtor]
../../../dist/include/nsProxyRelease.h: In instantiation of ‘nsrefcnt nsMainThreadPtrHolder<T>::Release() [with T = nsIUrlClassifierCallback; nsrefcnt = unsigned int]’:
../../../dist/include/nsAutoPtr.h:874:13:   required from ‘nsRefPtr<T>::~nsRefPtr() [with T = nsMainThreadPtrHolder<nsIUrlClassifierCallback>]’
../../../dist/include/nsProxyRelease.h:159:7:   required from here
../../../dist/include/nsProxyRelease.h:156:356: warning: deleting object of polymorphic class type ‘nsMainThreadPtrHolder<nsIUrlClassifierCallback>’ which has non-virtual destructor might cause undefined behaviour [-Wdelete-non-virtual-dtor]
../../../dist/include/nsProxyRelease.h: In instantiation of ‘nsrefcnt nsMainThreadPtrHolder<T>::Release() [with T = nsIUrlClassifierUpdateObserver; nsrefcnt = unsigned int]’:
../../../dist/include/nsAutoPtr.h:874:13:   required from ‘nsRefPtr<T>::~nsRefPtr() [with T = nsMainThreadPtrHolder<nsIUrlClassifierUpdateObserver>]’
../../../dist/include/nsProxyRelease.h:159:7:   required from here
../../../dist/include/nsProxyRelease.h:156:356: warning: deleting object of polymorphic class type ‘nsMainThreadPtrHolder<nsIUrlClassifierUpdateObserver>’ which has non-virtual destructor might cause undefined behaviour [-Wdelete-non-virtual-dtor]
nsUrlClassifierProxies.cpp
In file included from /scratch/work/builds/mozilla-central/mozilla-central.10-12-09.12-05/mozilla/toolkit/components/url-classifier/nsUrlClassifierProxies.h:10:0,
                 from /scratch/work/builds/mozilla-central/mozilla-central.10-12-09.12-05/mozilla/toolkit/components/url-classifier/nsUrlClassifierProxies.cpp:6:
../../../dist/include/nsProxyRelease.h: In instantiation of ‘nsrefcnt nsMainThreadPtrHolder<T>::Release() [with T = nsIUrlClassifierLookupCallback; nsrefcnt = unsigned int]’:
../../../dist/include/nsAutoPtr.h:874:13:   required from ‘nsRefPtr<T>::~nsRefPtr() [with T = nsMainThreadPtrHolder<nsIUrlClassifierLookupCallback>]’
../../../dist/include/nsProxyRelease.h:159:7:   required from here
../../../dist/include/nsProxyRelease.h:156:356: warning: deleting object of polymorphic class type ‘nsMainThreadPtrHolder<nsIUrlClassifierLookupCallback>’ which has non-virtual destructor might cause undefined behaviour [-Wdelete-non-virtual-dtor]
../../../dist/include/nsProxyRelease.h: In instantiation of ‘nsrefcnt nsMainThreadPtrHolder<T>::Release() [with T = nsIUrlClassifierCallback; nsrefcnt = unsigned int]’:
../../../dist/include/nsAutoPtr.h:874:13:   required from ‘nsRefPtr<T>::~nsRefPtr() [with T = nsMainThreadPtrHolder<nsIUrlClassifierCallback>]’
../../../dist/include/nsProxyRelease.h:159:7:   required from here
../../../dist/include/nsProxyRelease.h:156:356: warning: deleting object of polymorphic class type ‘nsMainThreadPtrHolder<nsIUrlClassifierCallback>’ which has non-virtual destructor might cause undefined behaviour [-Wdelete-non-virtual-dtor]
../../../dist/include/nsProxyRelease.h: In instantiation of ‘nsrefcnt nsMainThreadPtrHolder<T>::Release() [with T = nsIUrlClassifierUpdateObserver; nsrefcnt = unsigned int]’:
../../../dist/include/nsAutoPtr.h:874:13:   required from ‘nsRefPtr<T>::~nsRefPtr() [with T = nsMainThreadPtrHolder<nsIUrlClassifierUpdateObserver>]’
../../../dist/include/nsProxyRelease.h:159:7:   required from here
../../../dist/include/nsProxyRelease.h:156:356: warning: deleting object of polymorphic class type ‘nsMainThreadPtrHolder<nsIUrlClassifierUpdateObserver>’ which has non-virtual destructor might cause undefined behaviour [-Wdelete-non-virtual-dtor]
}

Easy to fix -- we just need to declare nsMainThreadPtrHolder as MOZ_FINAL, so the compiler doesn't worry about potential subclasses trying & failing to override its destructor.

Comment 1

[Daniel Holbert [:dholbert]]

Attachment: fix

Comment 2

[Daniel Holbert [:dholbert]]

FWIW, this warning started with the landing of bug 795281, which added the first instantiation of nsMainThreadPtrHolder<> into the tree.

Comment 3

[Bobby Holley (:bholley)]

Yeah, that was one of the patches from a big patch stack I had, but gcp landed it earlier to fix some other stuff. I'm pretty sure this fix is also somewhere in my stack, but please go ahead and land this. Sorry for the trouble. :-)

Comment 4

[Daniel Holbert [:dholbert]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/7b2ba9e2d17f

Comment 5

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/7b2ba9e2d17f

Comment 6

[Mike Habicher [:mikeh] (high bugzilla latency)]

https://hg.mozilla.org/releases/mozilla-b2g18/rev/ea47019235c0