StreamerElement retrieved from file has incorrect element name for (some) arrays. #8033
Description
This was first reported at: https://cdcvs.fnal.gov/redmine/issues/25615
with the error:
Fatal Root Error: TBranchElement::InitializeOffsets
Could not find the real data member 'fOutputNames' when constructing the branch '4anab::MVADescriptions_emtrkmichelid_emtrkmichel_Reco1.obj' [Likely an internal error, please report to the developers].
ROOT severity: 6000
during the creation of a branch.
With a class like:
class mystrarray {
public:
string fDataTag; ///< offset= 0 type=300 ,stl=365, ctype=365, Tag of the reco data products (art::InputTag format)
string fOutputInstance; ///< offset= 32 type=300 ,stl=365, ctype=365, Instance name of the feature vector collection
string fOutputNames[4]; ///< offset= 64 type=320 ,stl=365, ctype=365, Feature vector entries names/meaning
static short Class_Version() { return 10; }
};
creating any split branch containing this kind of object (or collection there of) will work fine.
But if a file containing the StreamerInfo for mystrarray version 10 before loading the library containing its dictionary then the StreamerInfo from the file (since it has the same checksum has the one that would come from the dictionary info) is used.
However, instead of
root [1] TClass::GetClass("mystrarray")->GetStreamerInfo()->GetElement(2)->GetFullName()
(const char *) "fOutputNames[4]"
it produces:
root [1] TClass::GetClass("mystrarray")->GetStreamerInfo()->GetElement(2)->GetFullName()
(const char *) "fOutputNames"
Which does not match the expectation of TBranchElement::InitializeOffsets.