[smart_holder] Demonstrate ODR VIOLATION DETECTED for PR #4395

[rwgk]

Description

See the description of PR #4022 for background.

clang++ -o pybind11/tests/test_stl.os -c -std=c++17 -fPIC -fvisibility=hidden -O0 -g -Wall -Wextra -Wconversion -Wcast-qual -Wdeprecated -Wundef -Wnon-virtual-dtor -Wunused-result -Werror -isystem /usr/include/python3.10 -isystem /usr/include/eigen3 -DPYBIND11_STRICT_ASSERTS_CLASS_HOLDER_VS_TYPE_CASTER_MIX -DPYBIND11_ENABLE_TYPE_CASTER_ODR_GUARD_IF_AVAILABLE -DPYBIND11_TEST_BOOST -Ipybind11/include -I/usr/local/google/home/rwgk/forked/pybind11/include -I/usr/local/google/home/rwgk/clone/pybind11/include /usr/local/google/home/rwgk/forked/pybind11/tests/test_stl.cpp
...
Running tests in directory "/usr/local/google/home/rwgk/forked/pybind11/tests":
terminate called after throwing an instance of 'std::system_error'
  what():  ODR VIOLATION DETECTED: pybind11::detail::type_caster<std::map<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, double, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, double> > >>: SourceLocation1="/usr/local/google/home/rwgk/forked/pybind11/include/pybind11/stl.h:161", SourceLocation2="/usr/local/google/home/rwgk/forked/pybind11/include/pybind11/detail/type_caster_base.h:913": State not recoverable

Suggested changelog entry:

[rwgk]

Links to CI results:

96 failing, 2 skipped, and 45 successful checks

• CI: https://github.com/pybind/pybind11/actions/runs/3667642607
• CI-SH-DEF: https://github.com/pybind/pybind11/actions/runs/3667642609