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Fix incorrect field offsets when parsing ETW events with fixed-count array fields #2427

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Merged
brianrob merged 2 commits into from
May 28, 2026
Merged

Fix incorrect field offsets when parsing ETW events with fixed-count array fields #2427

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56c7eec
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Copilot May 26, 2026
400e27e
Fix fixed array payload offset bug in RegisteredTraceEventParser
Copilot May 26, 2026
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12 changes: 11 additions & 1 deletion src/TraceEvent/RegisteredTraceEventParser.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1046,7 +1046,17 @@ private DynamicTraceEventData.PayloadFetchClassInfo ParseFields(int startField,
else
{
Debug.WriteLine(" Field is an array of size " + ((fixedCount != 0) ? fixedCount.ToString() : "VARIABLE") + " of type " + ((propertyFetch.Type ?? typeof(void))) + " at offset " + arrayFieldOffset.ToString("x"));
propertyFetch = DynamicTraceEventData.PayloadFetch.ArrayPayloadFetch(arrayFieldOffset, propertyFetch, arraySize, fixedCount, projectCharArrayAsString:false);
if (fixedCount != 0)
{
// Use FixedCountArrayPayloadFetch so that Size is set to the total byte size
// (fixedCount * element.Size) rather than just the element count, ensuring that
// subsequent field offsets are computed correctly.
propertyFetch = DynamicTraceEventData.PayloadFetch.FixedCountArrayPayloadFetch(arrayFieldOffset, propertyFetch, fixedCount, projectCharArrayAsString:false);
}
else
{
propertyFetch = DynamicTraceEventData.PayloadFetch.ArrayPayloadFetch(arrayFieldOffset, propertyFetch, arraySize, 0, projectCharArrayAsString:false);
}
}

fieldOffset = ushort.MaxValue; // Indicate that the next offset must be computed at run time.
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