PyROOT / cppyy: potentially ineffcicient "member offset" on enumerators

Running ROOT.TParameter["char"]().Print() triggers the following backtrace:

#6  0x00007f5aa1508536 in cling::Interpreter::EvaluateInternal (this=0x55c3b6db88f0, 
    input="TParameter<char>::kMultiply;", CO=..., V=0x7ffeae65ef40, wrapPoint=45)
    at /home/axel/build/root/master2/src/interpreter/cling/lib/Interpreter/Interpreter.cpp:1379
#7  0x00007f5aa1506307 in cling::Interpreter::process (this=0x55c3b6db88f0, 
    input="TParameter<char>::kMultiply;", V=0x7ffeae65ef40, T=0x0, disableValuePrinting=false)
    at /home/axel/build/root/master2/src/interpreter/cling/lib/Interpreter/Interpreter.cpp:840
#8  0x00007f5aa175d89a in cling::MetaProcessor::process (this=0x55c3b78351a0, input_line=..., 
    compRes=@0x7ffeae65eefc: cling::Interpreter::kSuccess, result=0x7ffeae65ef40, disableValuePrinting=false)
    at /home/axel/build/root/master2/src/interpreter/cling/lib/MetaProcessor/MetaProcessor.cpp:341
#9  0x00007f5aa12b19c0 in HandleInterpreterException (metaProcessor=0x55c3b78351a0, 
    input_line=0x55c3bb82fd10 "TParameter<char>::kMultiply;", 
    compRes=@0x7ffeae65eefc: cling::Interpreter::kSuccess, result=0x7ffeae65ef40)
    at /home/axel/build/root/master2/src/core/metacling/src/TCling.cxx:2448
#10 0x00007f5aa12b265d in TCling::ProcessLine (this=0x55c3b6cef830, 
    line=0x55c3bb8310e0 "TParameter<char>::kMultiply;", error=0x0)
    at /home/axel/build/root/master2/src/core/metacling/src/TCling.cxx:2608
#11 0x00007f5aa710b936 in Cppyy::GetDatamemberOffset (scope=18, idata=3)
    at /home/axel/build/root/master2/src/bindings/pyroot/cppyy/cppyy-backend/clingwrapper/src/clingwrapper.cxx:1995
#12 0x00007f5aa7288e96 in CPyCppyy::BuildScopeProxyDict (scope=18, pyclass=0x55c3bb8545f0)
    at /home/axel/build/root/master2/src/bindings/pyroot/cppyy/CPyCppyy/src/ProxyWrappers.cxx:353
#13 0x00007f5aa728a648 in CPyCppyy::CreateScopeProxy (name="TParameter<char>", parent=0x55c3b870c0b0)
    at /home/axel/build/root/master2/src/bindings/pyroot/cppyy/CPyCppyy/src/ProxyWrappers.cxx:681
#14 0x00007f5aa7265443 in (anonymous namespace)::MakeCppTemplateClass (args=0x7f5a8ad24ec0)
    at /home/axel/build/root/master2/src/bindings/pyroot/cppyy/CPyCppyy/src/CPyCppyyModule.cxx:368

That seems unnecessary; TClass and friends should know it's an enumerator and should know the value of it.

Currently TParameter<char> does not have a provided dictionary:

$ rg -g \*LinkDef\* TParameter
core/base/inc/LinkDef3.h
266:#pragma link C++ class TParameter<Bool_t>+;
267:#pragma link C++ class TParameter<Float_t>+;
268:#pragma link C++ class TParameter<Double_t>+;
269:#pragma link C++ class TParameter<Int_t>+;
270:#pragma link C++ class TParameter<Long_t>+;
271:#pragma link C++ class TParameter<Long64_t>+;

I don't think that's relevant to the issue :-) I tried to avoid any type that might have been instantiated already somewhere else, and with TParameter<char> I was positive that's not the case. You could also try with std::vector<TObject******> - if that had an enum member :-)

This is now

IncrementalExecutor::executeFunction: symbol '_ZN10TParameterIcE8StreamerER7TBuffer' unresolved while linking symbol '__cf_7'!
You are probably missing the definition of TParameter<char>::Streamer(TBuffer&)
Maybe you need to load the corresponding shared library?
IncrementalExecutor::executeFunction: symbol '_ZN10TParameterIcE5ClassEv' unresolved while linking symbol '__cf_7'!
You are probably missing the definition of TParameter<char>::Class()
Maybe you need to load the corresponding shared library?

#7  0x00007f5aa1506307 in cling::Interpreter::process (this=0x55c3b6db88f0, 
    input="TParameter<char>::kMultiply;", V=0x7ffeae65ef40, T=0x0, disableValuePrinting=false)
    at /home/axel/build/root/master2/src/interpreter/cling/lib/Interpreter/Interpreter.cpp:840

That's practically the same area as #14287 For some reason cppyy does not go via the offset interface...

[core] Provide TParameter dictionaries for all arithmetic types

Original problem fixed by #21261, follow-up reported in #10724 (comment) fixed by #23613. Both fixes were merged in the 6.42 release cycle.

A regression test that ensures these member offset queries don't go through the interpreter anymore is proposed in CppInterOp:

[test] Check that enumerator queries don't go through the interpreter compiler-research/CppInterOp#1144

[core] Provide TParameter dictionaries for all arithmetic types

[test] Check that enumerator queries don't go through the interpreter

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PyROOT / cppyy: potentially ineffcicient "member offset" on enumerators #10724

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PyROOT / cppyy: potentially ineffcicient "member offset" on enumerators #10724

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pcanal commented on Jun 9, 2022

Axel-Naumann commented on Jun 9, 2022

dpiparo commented on Feb 4, 2024

vgvassilev commented on Feb 4, 2024

guitargeek commented on Oct 8, 2026

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