[wasm][coreclr] Fix struct layout #122704
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Fixes dotnet#122294 The default layout is now equal to the C struct layout. The auto layout is updated in the same way.
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Pull request overview
This PR fixes struct layout alignment for WebAssembly (WASM) in CoreCLR to match C language struct layout rules. The changes ensure that when a type requires 8-byte alignment on WASM, the actual field alignment requirement is consulted rather than hardcoding the alignment to 8 bytes, which aligns the behavior with C struct layout semantics.
- Updates auto layout handling to use actual field alignment requirements on WASM when types require 8-byte alignment
- Updates default layout handling with the same WASM-specific logic for consistency
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Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| src/coreclr/vm/methodtablebuilder.cpp | Adds TARGET_WASM-specific logic in auto layout to use max(8, GetFieldAlignmentRequirement()) instead of hardcoded 8-byte alignment |
| src/coreclr/vm/classlayoutinfo.cpp | Adds TARGET_WASM-specific logic in default layout to use max(8, GetFieldAlignmentRequirement()) instead of hardcoded 8-byte alignment |
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cc @jkoritzinsky @davidwrighton - field layout algorithm change |
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…or types with GC references
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jkoritzinsky
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jkoritzinsky
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This was referenced Jan 6, 2026
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davidwrighton
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This reverts commit d278c46.
This was referenced Jan 9, 2026
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Fixes #122294
The default layout is now equal to the struct layout in C. The auto layout is updated in the same way.