Fix last sample dropped in cdbstack and set sample metric

Co-authored-by: brianrob <[email protected]>

Author: Copilot

src/PerfView.Tests/DebuggerStackSourceTests.cs

@@ -0,0 +1,78 @@
+using Diagnostics.Tracing.StackSources;
+using Microsoft.Diagnostics.Tracing.Stacks;
+using System.IO;
+using Xunit;
+
+namespace PerfViewTests
+{
+    public class DebuggerStackSourceTests
+    {
+        [Fact]
+        public void TestLastSampleIsNotDropped()
+        {
+            // Create a sample cdbstack file with two samples
+            var cdbStackContent = @"Call Site
+coreclr!JIT_MonEnterWorker_Portable
+System_Windows_ni!MS.Internal.ManagedPeerTable.TryGetManagedPeer(IntPtr, Boolean, System.Object ByRef)
+Call Site
+kernel32!BaseThreadInitThunk
+ntdll!RtlUserThreadStart";
+
+            DebuggerStackSource stackSource;
+            using (var reader = new StringReader(cdbStackContent))
+            {
+                stackSource = new DebuggerStackSource(reader);
+            }
+
+            // Count the samples
+            int sampleCount = 0;
+            stackSource.ForEach(sample => sampleCount++);
+
+            // We should have 2 samples, but the bug causes only 1 to be added
+            Assert.Equal(2, sampleCount);
+        }
+
+        [Fact]
+        public void TestSingleSampleIsAdded()
+        {
+            // Create a sample cdbstack file with a single sample (no subsequent "Call Site")
+            var cdbStackContent = @"Call Site
+coreclr!JIT_MonEnterWorker_Portable
+System_Windows_ni!MS.Internal.ManagedPeerTable.TryGetManagedPeer(IntPtr, Boolean, System.Object ByRef)";
+
+            DebuggerStackSource stackSource;
+            using (var reader = new StringReader(cdbStackContent))
+            {
+                stackSource = new DebuggerStackSource(reader);
+            }
+
+            // Count the samples
+            int sampleCount = 0;
+            stackSource.ForEach(sample => sampleCount++);
+
+            // We should have 1 sample
+            Assert.Equal(1, sampleCount);
+        }
+
+        [Fact]
+        public void TestSampleMetricIsSet()
+        {
+            // Create a sample cdbstack file with one sample
+            var cdbStackContent = @"Call Site
+coreclr!JIT_MonEnterWorker_Portable
+System_Windows_ni!MS.Internal.ManagedPeerTable.TryGetManagedPeer(IntPtr, Boolean, System.Object ByRef)";
+
+            DebuggerStackSource stackSource;
+            using (var reader = new StringReader(cdbStackContent))
+            {
+                stackSource = new DebuggerStackSource(reader);
+            }
+
+            // Check that metric is set to 1 for each sample
+            stackSource.ForEach(sample =>
+            {
+                Assert.Equal(1, sample.Metric);
+            });
+        }
+    }
+}

src/PerfView/OtherSources/DebuggerStackSource.cs

@@ -102,6 +102,7 @@ private void Read(TextReader reader)
 
                             stack.Clear();
 
+                            sample.Metric = 1;
                             sample.StackIndex = parent;
                             sample.TimeRelativeMSec = time;
                             time++;
@@ -112,6 +113,25 @@ private void Read(TextReader reader)
                     }
                 }
             }
+            
+            // Handle the last sample if there are any remaining frames
+            if (stack.Count != 0)
+            {
+                StackSourceCallStackIndex parent = StackSourceCallStackIndex.Invalid;
+                for (int i = stack.Count - 1; i >= 0; --i)
+                {
+                    parent = Interner.CallStackIntern(stack[i].frame, parent);
+                }
+
+                stack.Clear();
+
+                sample.Metric = 1;
+                sample.StackIndex = parent;
+                sample.TimeRelativeMSec = time;
+                time++;
+                AddSample(sample);
+            }
+            
             Interner.DoneInterning();
         }
         #endregion