Fix cross-module interface field/method vtable index mismatch#252
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Interface vtable slot numbers were assigned by two inconsistent algorithms: declaration-time assignment used raw interleaved declaration order, while cast-time assignment (getVirtualTable) always puts methods before fields. Whichever module performs an actual cast keeps the correct methods-first layout; a module that only reads an already-typed interface value it imported never runs the cast-time algorithm and keeps the stale declaration-order index, so a field read could land on a method's vtable slot (a function pointer misread as a byte offset) and crash the JIT with 0xC0000005. Add InterfaceInfo::assignCanonicalVirtualIndexes(), a pure function of the interface's own declaration, computed once when the declaration finishes resolving so all modules that re-parse it agree. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
This was referenced Jul 19, 2026
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Summary
InterfaceInfo::fields/methods'svirtualIndex) were assigned by two inconsistent algorithms: declaration-time assignment used raw interleaved declaration order, while cast-time assignment (getVirtualTable) always puts all methods before all fields.A.counter.countwhereA.counterisexported from another compiled module) never triggers the cast-time algorithm, so it kept the stale declaration-order index while the exporting module's real vtable used the methods-first layout - a field read could land on a method's vtable slot (a function pointer misread as athisVal-relative byte offset) and crash the JIT with0xC0000005.InterfaceInfo::assignCanonicalVirtualIndexes()computes the canonical (extends-offset, then methods in order, then fields in order) layout once when an interface declaration finishes resolving, independent of any cast - so every module that parses/re-parses the same interface declaration (including the@dllimporttextual redeclaration path used for-sharedimports) agrees on slot numbers.Counterinterface field/method regression coverage inexport_object_literal_with_interface.ts/import_object_literal_with_interface.tsthat was previously reverted (crashing) while this bug was still open.Test plan
ctest -R export-import-object-literal-with-interface(both AOT and JIT variants) now passctest -C Debug- 714/714 passed, no regressions🤖 Generated with Claude Code