Fix weak_ptr conversions, preserving control blocks for expired objects #1104
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
CaseyCarter
approved these changes
Jul 29, 2020
CaseyCarter
approved these changes
Jul 30, 2020
CaseyCarter
approved these changes
Jul 30, 2020
BillyONeal
approved these changes
Jul 31, 2020
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Outdated suggestions cannot be applied.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 #1102. This adds a few comments to the product code, explaining what's going on. Then, I enhanced our existing test for
weak_ptrconversions to testowner_beforeand then useowner_beforeto test that control blocks are preserved. Finally, I added a small test for the behavior of virtual inheritance conversions before the object expired, since we weren't actually testing that.Performance note: it would be possible to detect
T*toconst T*and avoid the_Incref_nz(which we did before this PR too, in the form of_Other.lock()); I could file an issue about that after merging this PR if anyone is interested. At this time, we don't know if it's possible to detect virtual base traversal in general, without a compiler builtin.