[clang][ExprConst] Diagnose ptr subs with non-zero offset

Author: tbaederr

clang/lib/AST/ExprConstant.cpp

@@ -14764,9 +14764,6 @@ bool IntExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
     // Reject differing bases from the normal codepath; we special-case
     // comparisons to null.
     if (!HasSameBase(LHSValue, RHSValue)) {
-      // Handle &&A - &&B.
-      if (!LHSValue.Offset.isZero() || !RHSValue.Offset.isZero())
-        return Error(E);
       const Expr *LHSExpr = LHSValue.Base.dyn_cast<const Expr *>();
       const Expr *RHSExpr = RHSValue.Base.dyn_cast<const Expr *>();
 

clang/test/SemaCXX/constant-expression-cxx11.cpp

@@ -409,6 +409,10 @@ constexpr int a = 0;
 constexpr int b = 1;
 constexpr int n = &b - &a; // expected-error {{must be initialized by a constant expression}} \
                            // expected-note {{arithmetic involving unrelated objects '&b' and '&a' has unspecified value}}
+constexpr static int arrk[2] = {1,2};
+constexpr static int arrk2[2] = {3,4};
+constexpr int k2 = &arrk[1] - &arrk2[0]; // expected-error {{must be initialized by a constant expression}} \
+                                         // expected-note {{arithmetic involving unrelated objects}}
 
 namespace MaterializeTemporary {