About CoInitializeEx

Julien Nabet serval2412 at yahoo.fr
Fri May 29 22:06:17 UTC 2020

On 29/05/2020 17:19, Mike Kaganski wrote:
> On 29.05.2020 17:41, julien2412 wrote:
>> ...
> Ctor of ODriver should store the previous status if COM initialization,
> if it wants to re-initialize it with a specific concurrency. It should
> check the failure code to detect if it was rejected because of different
> mode (RPC_E_CHANGED_MODE); and if so, it should call CoUninitialize as
> many times as needed to succeed with CoInitializeEx; then it needs to
> additionally call CoInitializeEx the same number of times (so that the
> total number of initializations is increased by 1). Then in dtor, it
> should reverse that: if it hadn't needed to change mode in ctor, then
> just call CoUninitialize once; otherwise, call CoUninitialize as many
> times as needed to CoInitializeEx with old mode to succeed, then call
> CoInitializeEx as many times that total initialize count is decremented
> by 1 compared to before entering dtor. That should account for possible
> intermediate unpaired calls to CoInitialize(Ex)/CoUninitialize in the
> same thread, and make sure that the calling code is in ~consistent state
> ... (however even this is a hack, and it would be better to find out why
> does it need to change the mode at all - i.e., if we can make sure it
> always used in appartment-threaded code).

Thank you for your feedback Mike.

I submitted on gerrit https://gerrit.libreoffice.org/c/core/+/95174.

Just quote the comment I put in gerrit:

"It seems we don't need to count the number of times CoInitializeEx has 
been called. From 
"The success code S_FALSE deserves mention. Some methods use S_FALSE to 
mean, roughly, a negative condition that is not a failure. It can also 
indicate a "no-op"—the method succeeded, but had no effect. For example, 
the CoInitializeEx function returns S_FALSE if you call it a second time 
from the same thread"

For the rest, I tried to save initial state (if different from " 
COINIT_APARTMENTTHREADED") in ctr to reuse it in dtr.


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