Tentative version of #149648

Author: tbaederr

clang/lib/AST/ByteCode/Interp.h

@@ -1890,9 +1890,8 @@ inline bool CheckNull(InterpState &S, CodePtr OpPC) {
   if (Ptr.isZero()) {
     S.FFDiag(S.Current->getSource(OpPC),
              diag::note_constexpr_dereferencing_null);
-    return false;
+    return S.noteUndefinedBehavior();
   }
-
   return true;
 }
 

clang/test/AST/ByteCode/const-eval.c

@@ -180,6 +180,9 @@ typedef __INTPTR_TYPE__ intptr_t;
 const intptr_t A = (intptr_t)(((int*) 0) + 1);
 const intptr_t B = (intptr_t)(((char*)0) + 3);
 _Static_assert(A > B, "");
+int * GH149500_p = &(*(int *)0x400);
+static const void *GH149500_q = &(*(const struct sysrq_key_op *)0);
+
 #else
 #error :(
 #endif