Demonstration of Undefined Behavior in handling of shared_ptr holder.

Based on https://godbolt.org/z/4fdjaW by jorgbrown@ (thanks Jorg!).
This commit is contained in:
Ralf W. Grosse-Kunstleve 2020-12-19 16:11:39 -08:00
parent 96f7ce5444
commit bda49efb14
2 changed files with 56 additions and 0 deletions

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// Demonstration of Undefined Behavior in handling of shared_ptr holder,
// specifically:
// https://github.com/pybind/pybind11/blob/30eb39ed79d1e2eeff15219ac00773034300a5e6/include/pybind11/cast.h#L235
// `return reinterpret_cast<H &>(vh[1]);`
// indirectly casts a `shared_ptr<drvd>` reference to a `shared_ptr<base>`.
// `test_smart_ptr_private_first_base.py` fails with an AssertionError and
// a subsequent Segmentation Fault (Linux, clang++ -std=c++17).
#include <memory>
#include "pybind11_tests.h"
namespace pybind11_tests {
namespace smart_ptr_private_first_base {
struct base {
base() : base_id(100) {}
virtual ~base() = default;
virtual int id() const { return base_id; }
int base_id;
};
struct private_first_base { // Any class with a virtual function will do.
virtual void some_other_virtual_function() const {}
virtual ~private_first_base() = default;
};
struct drvd : private private_first_base, public base {
int id() const override { return 2 * base_id; }
};
inline std::shared_ptr<drvd> make_shared_drvd() {
return std::shared_ptr<drvd>(new drvd);
}
inline int pass_shared_base(std::shared_ptr<base> b) { return b->id(); }
TEST_SUBMODULE(smart_ptr_private_first_base, m) {
py::class_<base, std::shared_ptr<base>>(m, "base");
py::class_<drvd, base, std::shared_ptr<drvd>>(m, "drvd");
m.def("make_shared_drvd", make_shared_drvd);
m.def("pass_shared_base", pass_shared_base);
}
} // namespace smart_ptr_private_first_base
} // namespace pybind11_tests

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# -*- coding: utf-8 -*-
import pytest
from pybind11_tests import smart_ptr_private_first_base as m
def test_make_pass():
d = m.make_shared_drvd()
i = m.pass_shared_base(d)
assert i == 200