Fix casting of classes with mixed polymorphic inheritance #1084
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
A polymorphic class can inherit from a non-polymorphic base.
dean0x7d
force-pushed
the
fix-mixed-inheritance
branch
from
5b642fc
to
2ce3b6c
Compare
|
Fixed the MSVC linker error. |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
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.