================
@@ -1543,3 +1544,55 @@ namespace GH197403 {
}
static_assert(test() == 0);
}
+
+namespace GH223064 {
+ struct A {
+ int n;
+ };
+ struct B : A {} b[2];
+
+ constexpr int *base_array_element() {
+ A *p = b;
+ return &static_cast<B *>(p)[1].n;
+ }
+ static_assert(base_array_element() == &b[1].n);
+
+ constexpr int pointer_difference() {
+ A *p = b;
+ return p - p;
+ }
+ static_assert(pointer_difference() == 0);
----------------
adiroy28852 wrote:
What i understood, was,
`&b[1]` and `&b[0]` converted to `A*` point at the `A` base sub-objects of two
different `B` elements. These aren't elements of the same `A` array, so `p - q`
shouldn't be a constant expression, and clang should reject it. Kindly correct
if wrong.
would below be correct ?
```cpp
constexpr auto difference(A *p, A *q) {
return p - q; // expected-note {{subtracted pointers are not elements of the
same array}}
}
static_assert(difference(&b[1], &b[0]) == 1); // expected-error {{static
assertion expression is not an integral constant expression}} \
// expected-note {{in call to
'difference(&b[1], &b[0])'}}
```
Something like this?
https://github.com/llvm/llvm-project/pull/230599
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