#376 TOcRegistrar constructor throws exception when registry access fails (regression in 6.40)

[Erwin Lotter]

On the startup of an OLE server the TOcRegistrar constructor tries to update the LocalServer32 registry entry even if no registration option is set. This fails if user rights are not sufficient — silently in older versions, but terminating with an exception now. As a result, OLE servers cannot be run as a non-server application without admin rights.

As a possible cause for this change in behaviour I found the removal of the condition that exceptions are not thrown when TXBase::InstanceCount > 0 in TXRegistry::Check. See "TXBase::InstanceCount is not thread-safe" [bugs:#176].

[Erwin Lotter]

I can see two solutions to this issue:

a) Supressing exceptions due to access violations within the TOcRegistrar constructor.
b) Abandon server registration unless explicitely specified as a command-line option.

I personally would prefer solution b) although it breaks with traditional behaviour.
This traditional behaviour might have been introduced to allow to omit registration during installation. But nowadays there are lots of installers handling this task easily. And also, manual registration by a user will fail in most cases anyway.

Are there differing opinions?

[Vidar Hasfjord]

Hi Erwin,

I don't have a differing opinion, but here are some thoughts on the options you presented.

I recommend you ensure that runtime behaviour is the same as before for existing client code. However, if you really want to change the default behaviour, I recommend you make it so that old code breaks, i.e. so that old code reliant on the old default behaviour wont compile, thus alerting the users to the changed behaviour and forcing them to adapt the client code.

To get the best of both solutions, you can add a parameter to the TOcRegistrar that configures how it deals with this registration issue, with a default argument that configures the constructor to behave the traditional way.

[Erwin Lotter]

... you can add a parameter to the TOcRegistrar that configures ...

From time to time one wonders why one did not come to it himself.

I recommend you ensure that runtime behaviour is the same as before

In general I agree and I did it this way [r3784]. But I'm not sure if this is the best way here. It might be better to add the parameter in a way that a compiler error will occur, i.e. directly after 'cmdline', not at the end of the list.

By accident I have also commited "source\owlext\calcedit.cpp". Please cancel if already fixed.

[Vidar Hasfjord]

[ensure the same behaviour] In general I agree and I did it this way

Hm. Having looked at your revision, it seems to me that the default behaviour is now to throw, i.e. a change of behaviour compared to traditional behaviour. Does that mean that you now consider the traditional behaviour, i.e. the failure to throw, a bug?

It might be better to add the parameter in a way that a compiler error will occur,

I tend to agree — presuming there is a change of behaviour now. That said, I am not in a position to have a strong opinion either way.

By accident I have also commited "source\owlext\calcedit.cpp".

Thanks for noticing and fixing this regression. I have supplemented the log message for [r3784]. Note that you can edit log statements in the TortoiseSVN log dialog (right click).

[Erwin Lotter]

Does that mean that you now consider the traditional behaviour ... a bug?

I do so, at least in some way. But the reason I chose to throw by default was:
a) This preserves the behaviour as it is now - seems that I missunderstood you here.
b) Setting the default behaviour to not throw would also apply when registration options are given in the command line.

I moved the new parameter in front of 'cmdLine' now to force a compile error [r3785].

[Vidar Hasfjord]

I have now merged this fix into 6.44 [r3929]. The fix was released in OWLNext 6.44.1.