Fix casting of classes with mixed polymorphic inheritance #1084
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A polymorphic class can inherit from a non-polymorphic base.
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Fixed the MSVC linker error. |
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Fixes #1080.
When a polymorphic class inherits from a non-polymorphic base, casting between the two adds an offset to account for the vtable pointer. Exposing such a base and derived type to Python currently results in undefined behavior (in practice, a wrong variable value or segfault due to the pointer offset). This PR fixes this by detecting when this kind of mixed inheritance takes place and marks the types as non-simple just like multiple inheritance. Everything else is taken care of by the existing non-simple type caster path which accounts for offset bases.
One problem is that this fix requires a modification of the
internalsABI (bumpedPYBIND11_INTERNALS_VERSION), so it's not a candidate for v2.2.1. There are currently ways to work around this (I'll update the issue) so that could work for now and the fix could be merged for v2.3.