================
@@ -11791,6 +11791,26 @@ QualType Sema::CheckAdditionOperands(ExprResult &LHS,
ExprResult &RHS,
return PExp->getType();
}
+/// Determine whether the size of \p T is provably zero: some array dimension
+/// is provably zero or the base element type has zero size. A variable
+/// dimension that does not fold to an integer constant is assumed nonzero.
+static bool isProvablyZeroSize(const ASTContext &Ctx, QualType T) {
+ while (const ArrayType *AT = Ctx.getAsArrayType(T)) {
+ if (const auto *CAT = dyn_cast<ConstantArrayType>(AT)) {
+ if (CAT->isZeroSize())
+ return true;
+ } else if (const auto *VAT = dyn_cast<VariableArrayType>(AT)) {
+ if (const Expr *Bound = VAT->getSizeExpr())
----------------
AaronBallman wrote:
Can you add some C++ tests where the size expression is a dependent value, just
to be sure the behavior there is reasonable with and without instantiation?
e.g.,
```
template <int N>
int not_instantiated() {
int array[N];
return &array - &array; // no diagnostic
}
template <int N>
int instantiated() {
int array[N];
return &array - &array; // diagnostic
}
int x = instantiated<0>; // template instantiation note
int y = instantiated<1>; // okay
```
https://github.com/llvm/llvm-project/pull/217465
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