PyROOT `std.tuple_element` not working on macOS about root

[guitargeek]

Hi! You are having two different C++ interpreters running there. The one of ROOT and the one of cppyy. I don't really understand why you do that. Maybe it's an artifact of how you constructed the reproducer? What about using PyROOT all the way?

import ROOT

ROOT.gInterpreter.LoadText("""
#include <tuple>
#include <string>
using ATuple = std::tuple<int, float, std::string, double>;
""")
from ROOT import ATuple

ROOT.std.tuple_element[1, ATuple].type

If you mix the independent interpreters in such a crazy way that you use the types from PyROOT as template parameters for cppyy types, it's not surprising that it fails.

[tmadlener]

I think in this case the cppyy that we pick up is the one that comes bundled with ROOT¹, and this seems to be working in all other OS'es (or at least we have not yet heard any complaints) except for macOS. I simply assumed that ROOT will just forward to its cppyy internally which is why I went for cppyy directly.

Let me try via PyROOT to see if that indeed already solves this.

Footnotes

1. At least python -c 'import cppyy; print(cppyy.__file__)' yields <root-prefix>/lib/root/cppyy/__init__.py. ↩

[tmadlener]

Just tested this and we get the same error message:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: <class cppyy.gbl.tuple_element<1,tuple<int,float,string,double> > at 0x146607890> has no attribute 'type'. Full details:
  type object 'tuple_element<1,tuple<int,float,string,double> >' has no attribute 'type'
  'tuple_element<1,tuple<int,float,string,double> >::type' is not a known C++ class
  'type' is not a known C++ template
  'type' is not a known C++ enum
>>> 

This looks a bit like some mismatch between clang or libc++ versions(?), but I don't know where the specifics would enter in this case.

[guitargeek]

Ah okay, interesting I didn't know you would pick up the cppyy from ROOT like this! Will investigate further next week when I can reproduce it. Interestingly, on my computer it works, even your original reproducer! So I think you're right, there must be some mismatch that happens with ROOT in your environment.

[gaede]

Has there been any resolution to this issue ?
I observe the same error on a rather virgin macbook pro (coreI5, 14.3) after installing ROOT w/ homebrew (no LCG or Ke4hep stack involved).

[guitargeek]

@gaede, I still fail to reproduce the issue, but I'm intending to make the reproducer a unit test, hoping to see the failure on some of the platforms.

[gaede]

@guitargeek, excellent thanks. Then we hope that it can be reproduced - and fixed ;-)

[guitargeek]

It doesn't look like it can be reproduced so far :( Maybe after merging the roottest PR, we will see the failure at some point somewhere in the nightlies.

[gaede]

Strange that you cannot reproduce this on any macos. I see this error even with using cppyy standalone:

import cppyy
cppyy.cppdef("""
#include <tuple>
#include <string>
using ATuple = std::tuple<int, float, std::string, double>;
""")

from cppyy.gbl import ATuple

cppyy.gbl.std.tuple_element[1, ATuple].type

print( cppyy )

Gives with cppyy and no root in the path:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: <class cppyy.gbl.std.tuple_element<1,std::tuple<int,float,std::string,double>> at 0x7f9365f9b1d0> has no attribute 'type'. Full details:
  type object 'tuple_element<1,std::tuple<int,float,std::string,d' has no attribute 'type'
  'std::tuple_element<1,std::tuple<int,float,std::string,double>>::type' is not a known C++ class
  'type' is not a known C++ template
  'type' is not a known C++ enum
>>> print (cppyy)
<module 'cppyy' from '/usr/local/lib/python3.9/site-packages/cppyy/__init__.py'>

And of course the same error using the cppyy shipped with root 6.26.06 and 6.28.04.

So to me it seems cppyy cannot deal with std::tuple on macos.