[clang][Interp] Protect GetPtrField ops from unknown size arrays

Author: tbaederr

clang/lib/AST/Interp/Interp.h

@@ -1245,6 +1245,8 @@ inline bool GetPtrField(InterpState &S, CodePtr OpPC, uint32_t Off) {
     return false;
   if (!CheckRange(S, OpPC, Ptr, CSK_Field))
     return false;
+  if (!CheckArray(S, OpPC, Ptr))
+    return false;
   if (!CheckSubobject(S, OpPC, Ptr, CSK_Field))
     return false;
 

clang/test/AST/Interp/arrays.cpp

@@ -595,3 +595,12 @@ int test_multiarray22() {
 }
 
 #endif
+
+namespace ArrayMemberAccess {
+  struct A {
+    int x;
+  };
+  void f(const A (&a)[]) {
+    bool cond = a->x;
+  }
+}