Handle ILLink origins before first sequence point#129869
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Avoid throwing while formatting diagnostics whose IL offset precedes the first available PDB sequence point. Fall back to the first sequence point and cover the case with a focused MessageContainer test. Assisted-by: Copilot:gpt-5.5 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
This PR updates ILLink’s diagnostic origin formatting to handle method IL offsets that occur before the first available PDB sequence point, preventing MessageOrigin.ToString() from throwing when generating MSBuild-formatted messages. It also adds a regression test that constructs and round-trips a Cecil-generated assembly + Portable PDB to reproduce the offset shape.
Changes:
- Make
MessageOrigin.ToString()tolerate “origin before first sequence point” by falling back to the first available sequence point instead of throwing. - Add a targeted xUnit regression test that emits a Portable PDB where the only sequence point is after the first IL instruction, then verifies
ToMSBuildString()output.
Show a summary per file
| File | Description |
|---|---|
| src/tools/illink/src/linker/Linker/MessageOrigin.cs | Adjusts sequence point selection logic to avoid Last() throwing when no sequence point exists at/before the IL offset. |
| src/tools/illink/test/Mono.Linker.Tests/Tests/MessageContainerTests.cs | Adds a Cecil-based regression test covering an origin IL offset occurring before the first sequence point. |
Copilot's findings
- Files reviewed: 2/2 changed files
- Comments generated: 1
Keep the existing LINQ-based sequence point lookup but use LastOrDefault so diagnostics whose IL offset precedes the first sequence point fall back to the tool name instead of throwing, matching ILC behavior. Assisted-by: Copilot:gpt-5.5 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Fixes #129562.
MessageOrigin.ToString()assumed that every diagnostic IL offset has at least one PDB sequence point at or before that offset. Rewritten/generated IL can put a warning origin before the first sequence point, which madeLast()throw while ILLink flushed cached warnings.This changes the lookup to tolerate that shape by falling back to the first available sequence point, and adds a focused regression test that round-trips a Cecil-generated assembly/PDB to reproduce the real offset behavior.
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