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Fix the issue where PDBs generated by ILSpy do not match certain asse… #3629

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Merged
siegfriedpammer merged 1 commit into from
Dec 21, 2025
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Fix the issue where PDBs generated by ILSpy do not match certain asse… #3629

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3 changes: 2 additions & 1 deletion ICSharpCode.Decompiler/DebugInfo/PortablePdbWriter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -235,8 +235,9 @@ string BuildFileNameFromTypeName(TypeDefinitionHandle handle)

if (pdbId == null)
{
var debugDir = file.Reader.ReadDebugDirectory().FirstOrDefault(dir => dir.Type == DebugDirectoryEntryType.CodeView);
var debugDir = file.Reader.ReadDebugDirectory().LastOrDefault(dir => dir.Type == DebugDirectoryEntryType.CodeView);

@siegfriedpammer siegfriedpammer Dec 8, 2025

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is it always guaranteed to be the last entry? Wouldn't it make more sense to check that the extension is not .ni.pdb?

I did some testing by scanning all the .dlls on my machine and reading the DebugDirectory and it seems that at least the Microsoft compiler puts the non-native image entry last.

@sonyps5201314 sonyps5201314 Dec 8, 2025 •
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Yes, I actually considered adding a line like Debug.Assert(!portable.Path.EndsWith("ni.pdb")); for more robust verification, or to alert us to unexpected scenarios in the future.

However, after checking dotPeek's code, I noticed that they always iterate from the end. Trusting their implementation, I decided to simply omit that assertion.

@siegfriedpammer siegfriedpammer Dec 8, 2025

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Sounds good, could you add a comment to document the assumption? Thank you!

@sonyps5201314 sonyps5201314 Dec 8, 2025

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Of course, feel free to modify this further, or we can wait until an unexpected scenario arises before making adjustments.

Arguably, the most reliable method would be to reverse engineer the relevant code in the VS debugger to confirm the exact matching logic. However, I suspect that dotPeek has already done this, which is why I decided to adopt an approach similar to theirs.

@sonyps5201314 sonyps5201314 Dec 14, 2025

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Sounds good, could you add a comment to document the assumption? Thank you!

I didn't know how to describe this assumption, so I simply added a call to Debug.Assert in the latest commit to execute this assumption.

var portable = file.Reader.ReadCodeViewDebugDirectoryData(debugDir);
Debug.Assert(!portable.Path.EndsWith(".ni.pdb"));
pdbId = new BlobContentId(portable.Guid, debugDir.Stamp);
}

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