TLeaf::ReadBasket invalid write in TMVA test

[hahnjo]

After #10005 is merged, the test TMVA-CrossValidation-Serialise will fail due to a stack-use-after-return:

352: WRITE of size 4 at 0x7f7ff4e1b880 thread T0
352:     #0 0x7f800120c3b9 in frombuf(char*&, unsigned int*) /home/jhahnfel/ROOT/src/core/base/inc/Bytes.h:310:7
352:     #1 0x7f800120c2bc in frombuf(char*&, int*) /home/jhahnfel/ROOT/src/core/base/inc/Bytes.h:442:48
352:     #2 0x7f7ffe26e9d0 in TBufferFile::ReadInt(int&) /home/jhahnfel/ROOT/src/io/io/inc/TBufferFile.h:401:4
352:     #3 0x7f80011965fc in TLeafI::ReadBasket(TBuffer&) /home/jhahnfel/ROOT/src/tree/tree/src/TLeafI.cxx:165:9
352:     #4 0x7f8001055b29 in TBranch::ReadLeavesImpl(TBuffer&) /home/jhahnfel/ROOT/src/tree/tree/src/TBranch.cxx:2382:13
352:     #5 0x7f800106b4a9 in TBranch::GetEntry(long long, int) /home/jhahnfel/ROOT/src/tree/tree/src/TBranch.cxx:1691:4
352:     #6 0x7f800125eea0 in TTree::GetEntry(long long, int)::$_3::operator()() const /home/jhahnfel/ROOT/src/tree/tree/src/TTree.cxx:5628:23
352:     #7 0x7f800125d3c8 in TTree::GetEntry(long long, int) /home/jhahnfel/ROOT/src/tree/tree/src/TTree.cxx:5703:7
352:     #8 0x50a984 in TestContex::runApplicationPhase(TString) /home/jhahnfel/ROOT/src/tmva/tmva/test/crossvalidation/TestCrossValidationSerialise.cxx:188:13
352:     #9 0x50b2a3 in TestCvSerialise(TMVA::Types::EMVA, TString, TString) /home/jhahnfel/ROOT/src/tmva/tmva/test/crossvalidation/TestCrossValidationSerialise.cxx:231:7
352:     #10 0x50b6e2 in TestCrossValidationSerialise() /home/jhahnfel/ROOT/src/tmva/tmva/test/crossvalidation/TestCrossValidationSerialise.cxx:240:7
352:     #11 0x50b8b3 in main /home/jhahnfel/ROOT/src/tmva/tmva/test/crossvalidation/TestCrossValidationSerialise.cxx:255:4
352:     #12 0x7f7ffad0aca2 in __libc_start_main (/lib64/libc.so.6+0x3aca2)
352:     #13 0x42361d in _start (/home/jhahnfel/ROOT/build-clang-asan-debug/tmva/tmva/test/crossvalidation/testCrossValidationSerialise+0x42361d)
352:
352: Address 0x7f7ff4e1b880 is located in stack of thread T0 at offset 128 in frame
352:     #0 0x7f7feed1f30f in cling::LookupHelper::findType(llvm::StringRef, cling::LookupHelper::DiagSetting) const (/home/jhahnfel/ROOT/build-clang-asan-debug/lib/libCling.so+0xdd430f)

Note: There may be other problems in the test after this issue is fixed. Please check locally with an instrumented build that the test passes afterwards!

[hahnjo]

Note that I'm completely unsure if this is really Cling's fault. If not, we have to re-assign accordingly.

[Axel-Naumann]

This isn't cling; it's TLeaf reading an int into the wrong location. I'll need to debug which int that is; I suspect classID/I