FilterUtility: Replace some nested raw pointers by unique_ptr<>*

[yhabteab]

No description provided.

[Al2Klimov]

Riddle

➜  icinga2 git:(replace-some-raw-pointer-with-intrusive-ptr) curl -ksSu root:123456 -H 'Accept: application/json' -X PUT -d '{"attrs":{"check_command":"passive","enable_active_checks":false}}' https://127.0.0.1:5665/v1/objects/hosts/e;echo
curl: (52) Empty reply from server

➜  icinga2 git:(replace-some-raw-pointer-with-intrusive-ptr) curl -ksSu root:123456 -H 'Accept: application/json' -X PUT -d '{"attrs":{"check_command":"passive","enable_active_checks":false}}' https://127.0.0.1:5665/v1/objects/hosts/e;echo
curl: (7) Failed to connect to 127.0.0.1 port 5665 after 5 ms: Connection refused

➜  icinga2 git:(replace-some-raw-pointer-with-intrusive-ptr)

[julianbrost]

Given that this PR is based on my suggestion from #9408 (comment), why did you chose intrusive_ptr over unique_ptr? (I think it should be perfectly doable with unique_ptr, only objectqueryhandler.cpp would need a slightly more elaborate change.)

[yhabteab]

Given that this PR is based on my suggestion from #9408 (comment), why did you chose intrusive_ptr over unique_ptr?

We are constantly transferring the ownership of permissionFilter around in objectqueryhandler.cpp, how do you suppose that would look/work with unique_ptr<>? However, if you want some fricky code to workaround this, I can change it to unique_ptr<>, then you would have to keep moving it back and forth.

[julianbrost]

However, if you want some fricky code to workaround this, I can change it to unique_ptr<>, then you would have to keep moving it back and forth.

There's a way around this: put the unique_ptr in the map, everything else can be a reference to it. Hint: insert returns an iterator to the inserted element, this is useful for initializing that reference.

[Al2Klimov]

But keep in mind:

If rehashing occurs due to the insertion, all iterators are invalidated.

– https://en.cppreference.com/w/cpp/container/unordered_map/insert