Hi David, In order to organize the branches, ROOT has to build a detailed dictionary for all the classes involved (top level classes, but also all referenced classes). To build the dictionary, one has to build an instance of a class and invoke the class ShowMembers function. If the pointer specified to TTree::Branch is not null, ROOT will use the corresponding object to build the dictionary, otherwise it will call the class default constructor and will return the created object at the pointer address. You can use this object if you like or delete it. You can force your own object (created may be by a non-default constructor before calling TTree::Branch. Rene Brun David Chamont wrote: > > Hi, > > Given the following code : > > int main() > { > TROOT root("dummy","dummy") ; > TFile file("dummy.root","recreate") ; > int split = 99 ; > int bufsize = 16000 ; > RtSimHit * hit = 0 ; > TTree tree("T","CMS demo tree"); > tree.Branch("hit","RtSimHit",&hit,bufsize,split) ; > ... > > I observe that after the last call, the pointer hit > is not any more null. Is it on purpose ? If so, why ? > > David C.
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