[cDAC] Change FrameIdentifiers to be contract literals

src/coreclr/debug/runtimeinfo/datadescriptor.h

@@ -764,7 +764,7 @@ CDAC_GLOBAL_POINTER(GCThread, &::g_pSuspensionThread)
 
 // Add FrameIdentifier for all defined Frame types. Used to differentiate Frame objects.
 #define FRAME_TYPE_NAME(frameType) \
-    CDAC_GLOBAL_POINTER(frameType##Identifier, FrameIdentifier::frameType)
+    CDAC_GLOBAL(frameType##Identifier, nuint, (uint64_t)FrameIdentifier::frameType)
 
     #include "frames.h"
 #undef FRAME_TYPE_NAME

src/native/managed/cdacreader/Microsoft.Diagnostics.DataContractReader.Abstractions/Target.cs

@@ -119,6 +119,15 @@ public enum CorDebugPlatform : int
     /// <returns>A numeric value</returns>
     public abstract T ReadGlobal<T>(string name) where T : struct, INumber<T>;
 
+    /// <summary>
+    /// Read a well known global from the target process as a number in the target endianness
+    /// </summary>
+    /// <typeparam name="T">The numeric type to be read</typeparam>
+    /// <param name="name">The name of the global</param>
+    /// <param name="value">The numeric value read.</param>
+    /// <returns>True if a global is found, false otherwise.</returns>
+    public abstract bool TryReadGlobal<T>(string name, [NotNullWhen(true)] out T? value) where T : struct, INumber<T>;
+
     /// <summary>
     /// Read a value from the target in target endianness
     /// </summary>

src/native/managed/cdacreader/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/FrameHandling/FrameIterator.cs

@@ -144,19 +144,13 @@ private static FrameType GetFrameType(Target target, TargetPointer frameIdentifi
     {
         foreach (FrameType frameType in Enum.GetValues<FrameType>())
         {
-            TargetPointer foundFrameIdentifier;
-            try
+            if (target.TryReadGlobal(frameType.ToString() + "Identifier", out ulong? id))
             {
-                // not all Frames are in all builds, so we need to catch the exception
-                foundFrameIdentifier = target.ReadGlobalPointer(frameType.ToString() + "Identifier");
-                if (frameIdentifier == foundFrameIdentifier)
+                if (frameIdentifier == new TargetPointer(id.Value))
                 {
                     return frameType;
                 }
             }
-            catch (InvalidOperationException)
-            {
-            }
         }
 
         return FrameType.Unknown;

src/native/managed/cdacreader/Microsoft.Diagnostics.DataContractReader/ContractDescriptorTarget.cs

@@ -496,6 +496,22 @@ public bool IsAlignedToPointerSize(ulong value)
     public override bool IsAlignedToPointerSize(TargetPointer pointer)
         => IsAligned(pointer.Value, _config.PointerSize);
 
+    public override bool TryReadGlobal<T>(string name, [NotNullWhen(true)] out T? value)
+        => TryReadGlobal<T>(name, out value, out _);
+
+    public bool TryReadGlobal<T>(string name, [NotNullWhen(true)] out T? value, out string? type) where T : struct, INumber<T>
+    {
+        value = null;
+        type = null;
+        if (!_globals.TryGetValue(name, out (ulong Value, string? Type) global))
+        {
+            return false;
+        }
+        type = global.Type;
+        value = T.CreateChecked(global.Value);
+        return true;
+    }
+
     public override T ReadGlobal<T>(string name)
         => ReadGlobal<T>(name, out _);
 

src/native/managed/cdacreader/tests/TestPlaceholderTarget.cs

@@ -93,6 +93,20 @@ public override string ReadUtf16String(ulong address)
     }
 
     public override TargetNUInt ReadNUInt(ulong address) => DefaultReadNUInt(address);
+
+    public override bool TryReadGlobal<T>(string name, [NotNullWhen(true)] out T? value)
+    {
+        value = default;
+        foreach (var global in _globals)
+        {
+            if (global.Name == name)
+            {
+                value = T.CreateChecked(global.Value);
+                return true;
+            }
+        }
+        return false;
+    }
     public override T ReadGlobal<T>(string name)
     {
         foreach (var global in _globals)