Fix dbus::Property compile failure on gcc

Fix dbus::Property compile failure on gcc

This fixes build failure on gcc, that is introduced by http://crrev.com/285475.
The error log is http://paste.ubuntu.com/7853634/

[tzik, 2014-07-25 09:15:31]

Sorry for repeated try. Please take a look.
# Or, any suggestion to fix this by less annoying way?

[Nico, 2014-07-25 16:37:23]

https://codereview.chromium.org/419203003/diff/20001/dbus/property.h
File dbus/property.h (left):

https://codereview.chromium.org/419203003/diff/20001/dbus/property.h#oldcode412
dbus/property.h:412: extern template class CHROME_DBUS_EXPORT Property<uint8>;
Just removing the CHROME_DBUS_EXPORT should be enough to fix that error, no?

[Nico, 2014-07-25 16:46:50]

https://codereview.chromium.org/419203003/diff/20001/dbus/property.h
File dbus/property.h (left):

https://codereview.chromium.org/419203003/diff/20001/dbus/property.h#oldcode409
dbus/property.h:409: template <> Property<uint8>::Property();
…and this line is wrong too I think. Since the constructor is defined inline
above, you shouldn't instantiate it here, that'll lead to an instantiation of
the template, not to a specialization.

So I recommend:
* Remove all the ::Property() lines
* For consistency with other code, remove the CHROME_DBUS_EXPORT from the extern
template class liens

[tzik, 2014-07-29 05:52:36]

https://codereview.chromium.org/419203003/diff/20001/dbus/property.h
File dbus/property.h (left):

https://codereview.chromium.org/419203003/diff/20001/dbus/property.h#oldcode409
dbus/property.h:409: template <> Property<uint8>::Property();
On 2014/07/25 16:46:50, Nico (away) wrote:
> …and this line is wrong too I think. Since the constructor is defined inline
> above, you shouldn't instantiate it here, that'll lead to an instantiation of
> the template, not to a specialization.
> 
> So I recommend:
> * Remove all the ::Property() lines
> * For consistency with other code, remove the CHROME_DBUS_EXPORT from the
extern
> template class liens

These Property::Property()s seem specialization rather than instantiation.
property.cc provides slightly different implementation for them.

We can implement them uniformly like below, which is common way in Chromium:
Property() : value_(), set_value_() {}

https://codereview.chromium.org/419203003/diff/20001/dbus/property.h#oldcode412
dbus/property.h:412: extern template class CHROME_DBUS_EXPORT Property<uint8>;
On 2014/07/25 16:37:23, Nico (away) wrote:
> Just removing the CHROME_DBUS_EXPORT should be enough to fix that error, no?

That doesn't build successfully on clang+asan on latest clang, unfortunately.
The error message was same as the first try of the fix:
https://codereview.chromium.org/354553002#msg1

[Nico, 2014-07-29 22:14:02]

On 2014/07/29 05:52:36, tzik wrote:
> https://codereview.chromium.org/419203003/diff/20001/dbus/property.h
> File dbus/property.h (left):
> 
>
https://codereview.chromium.org/419203003/diff/20001/dbus/property.h#oldcode409
> dbus/property.h:409: template <> Property<uint8>::Property();
> On 2014/07/25 16:46:50, Nico (away) wrote:
> > …and this line is wrong too I think. Since the constructor is defined inline
> > above, you shouldn't instantiate it here, that'll lead to an instantiation
of
> > the template, not to a specialization.
> > 
> > So I recommend:
> > * Remove all the ::Property() lines
> > * For consistency with other code, remove the CHROME_DBUS_EXPORT from the
> extern
> > template class liens
> 
> These Property::Property()s seem specialization rather than instantiation.
> property.cc provides slightly different implementation for them.

Ah, you're correct again.

> > Just removing the CHROME_DBUS_EXPORT should be enough to fix that error, no?
> 
> That doesn't build successfully on clang+asan on latest clang, unfortunately.
> The error message was same as the first try of the fix:
> https://codereview.chromium.org/354553002#msg1

I can't reproduce that problem. I tried
https://codereview.chromium.org/424453003 (only part 2 of my suggestion), and
that seems to link dbus_unittests fine in a components build with gcc and clang
(both with and without asan), in both release and debug. Are you sure this
doesn't work?