Fix unsigned indexing with negative value on EnC (#72255)

FixContextForEnC was treating an index that may be negative as an
unsigned value. This would crash the runtime during EnC when running as
64-bit.

Fix #70834

src/coreclr/vm/eetwain.cpp

@@ -991,6 +991,7 @@ HRESULT EECodeManager::FixContextForEnC(PCONTEXT         pCtx,
     UINT32 oldSizeOfPreservedArea = oldGcDecoder.GetSizeOfEditAndContinuePreservedArea();
     UINT32 newSizeOfPreservedArea = newGcDecoder.GetSizeOfEditAndContinuePreservedArea();
 
+    LOG((LF_CORDB, LL_INFO100, "EECM::FixContextForEnC: Got old and new EnC preserved area sizes of %u and %u\n", oldSizeOfPreservedArea, newSizeOfPreservedArea));
     // This ensures the JIT generated EnC compliant code.
     if ((oldSizeOfPreservedArea == NO_SIZE_OF_EDIT_AND_CONTINUE_PRESERVED_AREA) ||
         (newSizeOfPreservedArea == NO_SIZE_OF_EDIT_AND_CONTINUE_PRESERVED_AREA))
@@ -1001,6 +1002,8 @@ HRESULT EECodeManager::FixContextForEnC(PCONTEXT         pCtx,
 
     TADDR oldStackBase = GetSP(&oldCtx);
 
+    LOG((LF_CORDB, LL_INFO100, "EECM::FixContextForEnC: Old SP=%p, FP=%p\n", (void*)oldStackBase, (void*)GetFP(&oldCtx)));
+
 #if defined(TARGET_AMD64)
     // Note: we cannot assert anything about the relationship between oldFixedStackSize
     // and newFixedStackSize.  It's possible the edited frame grows (new locals) or
@@ -1013,6 +1016,8 @@ HRESULT EECodeManager::FixContextForEnC(PCONTEXT         pCtx,
     _ASSERTE(pOldCodeInfo->HasFrameRegister());
     _ASSERTE(pNewCodeInfo->HasFrameRegister());
 
+    LOG((LF_CORDB, LL_INFO100, "EECM::FixContextForEnC: Old and new fixed stack sizes are %u and %u\n", oldFixedStackSize, newFixedStackSize));
+
     // x64: SP == FP before localloc
     if (oldStackBase != GetFP(&oldCtx))
         return E_FAIL;
@@ -1020,6 +1025,8 @@ HRESULT EECodeManager::FixContextForEnC(PCONTEXT         pCtx,
     DWORD oldFixedStackSize = oldGcDecoder.GetSizeOfEditAndContinueFixedStackFrame();
     DWORD newFixedStackSize = newGcDecoder.GetSizeOfEditAndContinueFixedStackFrame();
 
+    LOG((LF_CORDB, LL_INFO100, "EECM::FixContextForEnC: Old and new fixed stack sizes are %u and %u\n", oldFixedStackSize, newFixedStackSize));
+
     // ARM64: FP + 16 == SP + oldFixedStackSize before localloc
     if (GetFP(&oldCtx) + 16 != oldStackBase + oldFixedStackSize)
         return E_FAIL;
@@ -1128,7 +1135,7 @@ HRESULT EECodeManager::FixContextForEnC(PCONTEXT         pCtx,
             if (pOldVar->startOffset <= oldMethodOffset &&
                 pOldVar->endOffset   >  oldMethodOffset)
             {
-                oldMethodVarsSorted[varNumber] = *pOldVar;
+                oldMethodVarsSorted[(int)varNumber] = *pOldVar;
             }
         }
 
@@ -1180,7 +1187,7 @@ HRESULT EECodeManager::FixContextForEnC(PCONTEXT         pCtx,
             if (pNewVar->startOffset <= newMethodOffset &&
                 pNewVar->endOffset   >  newMethodOffset)
             {
-                newMethodVarsSorted[varNumber] = *pNewVar;
+                newMethodVarsSorted[(int)varNumber] = *pNewVar;
             }
         }