[tree] Change return type of TBranch::GetAddress() et al to void*

So far, the `TBranch::GetAddress` method returned a `char *`. This
causes incompatibility with PyROOT, because `char *` is automatically
converted to a Python string, which is the wrong thing to for an
address.

This made the return value unusable in PyROOT. That's a bug that
currently prevents us from reimplementing some pythonizations in native
Python.

Therefore, the return type of `TBranch::GetAddress()` was changed to
`void *` in this release. Even if this change is not backwards
compatible for typing reasons, the returned value is the same.

With this change, the code is also more consistent because
`GetAddress()` and `SetBranchAddress()` use the same type for the
address.

README/ReleaseNotes/v632/index.md

@@ -52,6 +52,7 @@ The following people have contributed to this new version:
 
 
 ## TTree Libraries
+
 ### Add files from subdirectories with `TChain::Add` globbing
 It is now possible to add files from multiple subdirectories with `TChain::Add` globbing. For example,
 ```
@@ -65,6 +66,28 @@ TChain::Add("/path/to/tree/subdir[0-9]/*.root")
 ```
 This grabs all the root files in subdirectories that have a name starting with `subdir` and ending with some digit.
 
+### Changing return type of TBranch::GetAddress() and others to `void *`
+
+So far, the `TBranch::GetAddress` method returned a `char *`. This causes
+incompatibility with PyROOT, because `char *` is automatically converted to a
+Python string, which is the wrong thing to for an address. This made the return
+value unusable in PyROOT.
+
+Therefore, the return type of `TBranch::GetAddress()` was changed to `void *`
+in this release. Even if this change is not backwards compatible for typing
+reasons, the returned value is the same. In case your C++ code doesn't compile
+because of this, just explicitly cast the return value to what you want with a
+C-style or better `reinterpret_cast`. Like this, your code will stay compatible
+with all ROOT versions. For example:
+```c++
+void *addr = reinterpret_cast<void *>(branch->GetAddress());
+```
+
+The same change also applies to other functions, the full list is here:
+
+  * TBranch::GetAddress()
+  * TBranchElement::GetObject()
+
 ## Histogram Libraries
 
 

bindings/pyroot/pythonizations/src/TTreePyz.cxx

@@ -65,7 +65,7 @@ static PyObject *BindBranchToProxy(TTree *tree, const char *name, TBranch *branc
       TBranchElement *be = (TBranchElement *)branch;
       if (be->GetCurrentClass() && (be->GetCurrentClass() != be->GetTargetClass()) && (0 <= be->GetID())) {
          Long_t offset = ((TStreamerElement *)be->GetInfo()->GetElements()->At(be->GetID()))->GetOffset();
-         return BindCppObjectNoCast(be->GetObject() + offset, Cppyy::GetScope(be->GetCurrentClass()->GetName()));
+         return BindCppObjectNoCast((char *)be->GetObject() + offset, Cppyy::GetScope(be->GetCurrentClass()->GetName()));
       }
    }
 

tree/tree/inc/TBranch.h

@@ -209,7 +209,7 @@ class TBranch : public TNamed, public TAttFill {
            Int_t     FlushBaskets();
            Int_t     FlushOneBasket(UInt_t which);
 
-   virtual char     *GetAddress() const {return fAddress;}
+   virtual void     *GetAddress() const {return (void*)fAddress;}
            TBasket  *GetBasket(Int_t basket) {return GetBasketImpl(basket, nullptr);}
            Int_t    *GetBasketBytes() const {return fBasketBytes;}
            Long64_t *GetBasketEntry() const {return fBasketEntry;}

tree/tree/inc/TBranchElement.h

@@ -178,7 +178,7 @@ class TBranchElement : public TBranch {
            void             Browse(TBrowser* b) override;
            TBranch         *FindBranch(const char *name) override;
            TLeaf           *FindLeaf(const char *name) override;
-           char            *GetAddress() const override;
+           void            *GetAddress() const override;
            TBranchElement  *GetBranchCount() const { return fBranchCount; }
            TBranchElement  *GetBranchCount2() const { return fBranchCount2; }
            Int_t           *GetBranchOffset() const { return fBranchOffset; }
@@ -195,7 +195,7 @@ class TBranchElement : public TBranch {
            Int_t            GetID() const { return fID; }
            TStreamerInfo   *GetInfo() const;
            bool             GetMakeClass() const override;
-           char            *GetObject() const;
+           void            *GetObject() const;
            TVirtualArray   *GetOnfileObject() const { return fOnfileObject; }
    virtual const char      *GetParentName() const { return fParentName.Data(); }
    virtual Int_t            GetMaximum() const;

tree/tree/src/TBranchElement.cxx

@@ -1920,10 +1920,10 @@ TLeaf* TBranchElement::FindLeaf(const char *name)
 ///
 /// - Return a pointer to our object.
 
-char* TBranchElement::GetAddress() const
+void* TBranchElement::GetAddress() const
 {
    ValidateAddress();
-   return fAddress;
+   return (void*)fAddress;
 }
 
 
@@ -2884,10 +2884,10 @@ Int_t TBranchElement::GetMaximum() const
 ////////////////////////////////////////////////////////////////////////////////
 /// Return a pointer to our object.
 
-char* TBranchElement::GetObject() const
+void* TBranchElement::GetObject() const
 {
    ValidateAddress();
-   return fObject;
+   return (void*)fObject;
 }
 
 ////////////////////////////////////////////////////////////////////////////////

tree/tree/src/TTree.cxx

@@ -3308,7 +3308,7 @@ void TTree::CopyAddresses(TTree* tree, bool undo)
          TBranch* br = tree->GetBranch(branch->GetName());
          tree->ResetBranchAddress(br);
       } else {
-         char* addr = branch->GetAddress();
+         void* addr = branch->GetAddress();
          if (!addr) {
             if (branch->IsA() == TBranch::Class()) {
                // If the branch was created using a leaflist, the branch itself may not have

tree/treeplayer/src/TFormLeafInfo.cxx

@@ -189,9 +189,9 @@ char* TFormLeafInfo::GetObjectAddress(TLeafElement* leaf, Int_t& instance)
       // Branch is a top-level branch.
       if (branch->GetTree()->GetMakeClass()) {
          // Branch belongs to a MakeClass tree.
-         return branch->GetAddress();
+         return (char*) branch->GetAddress();
       } else {
-         return branch->GetObject();
+         return (char*) branch->GetObject();
       }
    }
    TStreamerInfo* info = branch->GetInfo();
@@ -211,7 +211,7 @@ char* TFormLeafInfo::GetObjectAddress(TLeafElement* leaf, Int_t& instance)
    char* thisobj = nullptr;
    if (!address) {
       // FIXME: This makes no sense, if the branch address is not set, then object will not be set either.
-      thisobj = branch->GetObject();
+      thisobj = (char*) branch->GetObject();
    } else {
       Int_t type = -1;
       if (id > -1) {

tree/treeplayer/src/TTreeFormula.cxx

@@ -4480,11 +4480,11 @@ Double_t TTreeFormula::GetValueFromMethod(Int_t i, TLeaf* leaf) const
          }
       }
       if (id < 0) {
-         char* address = branch->GetObject();
+         char* address = (char*) branch->GetObject();
          thisobj = address;
       } else {
          //char* address = branch->GetAddress();
-         char* address = branch->GetObject();
+         char* address = (char*) branch->GetObject();
          if (address) {
             thisobj = *((char**) (address + offset));
          } else {
@@ -4540,11 +4540,11 @@ void* TTreeFormula::GetValuePointerFromMethod(Int_t i, TLeaf* leaf) const
          }
       }
       if (id < 0) {
-         char* address = branch->GetObject();
+         char* address = (char*) branch->GetObject();
          thisobj = address;
       } else {
          //char* address = branch->GetAddress();
-         char* address = branch->GetObject();
+         char* address = (char*) branch->GetObject();
          if (address) {
             thisobj = *((char**) (address + offset));
          } else {

tree/treeplayer/src/TTreeGeneratorBase.cxx

@@ -166,7 +166,7 @@ namespace Internal {
          Long64_t i = branch->GetTree()->GetReadEntry();
          if (i<0) i = 0;
          branch->GetEntry(i);
-         char *obj = branch->GetObject();
+         char *obj = (char*) branch->GetObject();
 
          TBranchElement *parent = (TBranchElement*)branch->GetMother()->GetSubBranch(branch);
          const char *pclname = parent->GetClassName();