[ios-clr] Throw descriptive error when a stripped IL body is needed at runtime

src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCasesRunner/R2RResultChecker.cs

@@ -1073,9 +1073,9 @@ public static bool MethodILIsStripped(string msilFilePath, string declaringType,
         if (!TryGetMethodIL(msilFilePath, declaringType, methodName, out byte[] il, out diagnostic))
             return false;
 
-        bool stripped = il.AsSpan().SequenceEqual((ReadOnlySpan<byte>)[0x14, 0x7A]);
+        bool stripped = il.AsSpan().SequenceEqual((ReadOnlySpan<byte>)[0xFE, 0x24]);
         diagnostic = stripped
-            ? $"IL of '{declaringType}.{methodName}' is stripped (ldnull; throw)."
+            ? $"IL of '{declaringType}.{methodName}' is stripped (invalid opcode 0xFE 0x24)."
             : $"Expected IL of '{declaringType}.{methodName}' to be stripped, but it is present ({il.Length} bytes: {BitConverter.ToString(il)}).";
         return stripped;
     }
@@ -1088,10 +1088,10 @@ public static bool MethodILIsPresent(string msilFilePath, string declaringType,
         if (!TryGetMethodIL(msilFilePath, declaringType, methodName, out byte[] il, out diagnostic))
             return false;
 
-        bool present = !il.AsSpan().SequenceEqual((ReadOnlySpan<byte>)[0x14, 0x7A]);
+        bool present = !il.AsSpan().SequenceEqual((ReadOnlySpan<byte>)[0xFE, 0x24]);
         diagnostic = present
             ? $"IL of '{declaringType}.{methodName}' is present ({il.Length} bytes)."
-            : $"Expected IL of '{declaringType}.{methodName}' to be present, but it was stripped (ldnull; throw).";
+            : $"Expected IL of '{declaringType}.{methodName}' to be present, but it was stripped (invalid opcode 0xFE 0x24).";
         return present;
     }
 }

src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/CopiedMethodILNode.cs

@@ -14,9 +14,9 @@ namespace ILCompiler.DependencyAnalysis.ReadyToRun
 {
     public class CopiedMethodILNode : ObjectNode, ISymbolDefinitionNode
     {
-        // Throws NullReferenceException if the stripped body is encountered.
-        // Tiny header (0x0A: 2 bytes code size) + ldnull (0x14) + throw (0x7A).
-        private static readonly byte[] s_minimalILBody = [0x0A, 0x14, 0x7A];
+        // Sentinel body for stripped IL methods: tiny header (0x0A) + invalid opcode 0xFE 0x24.
+        // Invalid IL so it can never collide with a real method body.
+        private static readonly byte[] s_minimalILBody = [0x0A, 0xFE, 0x24];
 
         EcmaMethod _method;
 

src/coreclr/vm/prestub.cpp

@@ -725,6 +725,17 @@ namespace
         if (status == COR_ILMETHOD_DECODER::FORMAT_ERROR)
             COMPlusThrowHR(COR_E_BADIMAGEFORMAT, BFA_BAD_IL);
 
+        Module* pModule = pMD->GetModule();
+        if (pModule->IsReadyToRun()
+            && pModule->GetReadyToRunInfo()->HasStrippedILBodies()
+            && pHeader->GetCodeSize() == 2
+            && pHeader->Code[0] == 0xFE
+            && pHeader->Code[1] == 0x24)
+        {
+            EEPOLICY_HANDLE_FATAL_ERROR_WITH_MESSAGE(COR_E_EXECUTIONENGINE,
+                W("A method body required at runtime was stripped from the ReadyToRun image."));
+        }
+
         return pHeader;
     }