FFL-1450 fix memory corruption in flag_metadata #1368
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dd-oleksii
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BenchmarksComparisonBenchmark execution time: 2025-11-24 21:01:13 Comparing candidate commit 067fd56 in PR branch Found 0 performance improvements and 0 performance regressions! Performance is the same for 55 metrics, 2 unstable metrics. CandidateCandidate benchmark detailsGroup 1
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BaselineOmitted due to size. |
Codecov Report❌ Patch coverage is Additional details and impacted files@@ Coverage Diff @@
## main #1368 +/- ##
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Coverage 71.19% 71.20%
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Files 392 392
Lines 62677 62751 +74
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+ Hits 44626 44684 +58
- Misses 18051 18067 +16
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sameerank
approved these changes
Nov 25, 2025
| .map(|(k, v)| { | ||
| KeyValue { | ||
| // SAFETY: the borrow is valid as long as string allocation is | ||
| // alive. ResolutionDetails will get moved into heap but this does not |
Contributor
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Ok I think I understand. ResolutionDetails moves, and since Assignment is owned directly by the struct due to inner: Result<Assignment, EvaluationError>, Assignment moves too. So,
let details = ResolutionDetails::new(Ok(value)); // details created
// BorrowedStr pointers in details are valid
let moved_details = details; // move happens
// now BorrowedStr pointers in moved_details are invalid
Thanks for updating the comments! They're helpful
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What does this PR do?
Fix a memory corruption bug in flag_metadata.
Additional Notes
Strtype has small string optimization, whereas short strings are stored directly in the structure bytes instead of on heap. This means that taking a reference to anallocation_keystring was pointing to an str structure which was stored on stack at that time and was moved out when result was returned from the structure. When trying to printflag_metadata.allocationKey, it was printing garbage bytes from stack.This PR stores result on heap first (
Box) and pins it for extra measure, to make sure it's not moved. This allows us to create stable pointers toallocation_key.How to test the change?
Example was expanded to print flag metadata, so verified that it was corrupted before / fixed after the change.