Add 'share_from_this' to 'torch::jit::Graph' (#87343)
Avoid passing raw pointer of 'torch::jit::Graph' to python. Otherwise, it will corrupt the
`internals::registered_instance` of pybind11, caching a holder for python w.r.t the raw
pointer of 'torch::jit::Graph', while not increasing the use count of the existing shared_ptr.
The behavior afterwards is random and probably undefined.
Most of the time it works, if the holder is deallocated timely on python side, and the
cache then cleared from `internals::registered_instance`. Things are back to normal.
Otherwise, it fails with either segfault or a runtime error of message "Unable to cast
from non-held to held instance". One of such scenarios is normally and correctly
returning a shared_ptr of that 'torch::jit::Graph' to python. Pybind finds the holder via
cache. Due to this, the shared_ptr use_count will not increase. If there is no other use
on C++ side, the graph will be freed, while python still has access, via the holder created
previously.
@t-vi had a great analysis and solution to this exact problem at #51833 which I hope
I had seen before debugging this issue... ~~I'm building the PR based on the original
commit. @t-vi please let me know if you'd prefer otherwise.~~ Sending the PR separately
due to CLA issues.
Need to check in CI if adding `enable_shared_from_this` breaks other stuff.
Fixes #51833, and CI issues in #87258, #86182.
cc @malfet, @kit1980 for changes on JIT IR.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/87343
Approved by: https://github.com/justinchuby, https://github.com/AllenTiTaiWang, https://github.com/malfet
