[PATCH] D149013: [clang][Interp] Check pointers when accessing base class

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added subscribers: hubert.reinterpretcast, rsmith.
aaron.ballman added inline comments.


================
Comment at: clang/test/AST/Interp/records.cpp:509-512
+  constexpr A *a2 = &b + 1; // expected-error {{must be initialized by a constant expression}} \
+                            // expected-note {{cannot access base class of pointer past the end of object}} \
+                            // ref-error {{must be initialized by a constant expression}} \
+                            // ref-note {{cannot access base class of pointer past the end of object}}
----------------
tbaeder wrote:
> cor3ntin wrote:
> > aaron.ballman wrote:
> > > I may have jumped the gun on accepting this, actually. Forming the pointer to `&b + 1` is fine, but evaluating it by dereferencing it would be UB. e.g., http://eel.is/c++draft/expr.const#13.3
> > We probably want tests that ensure `&b+2` is invalid in all cases
> It's being evaluated because the base class is accessed, isn't it? if `b` was of type `A*`, we would not emit a diagnostic (see line 506 above).
I'm not seeing the access to the base class -- we're forming a pointer, not dereferencing it.

https://godbolt.org/z/vxThqczeo

I think this is an existing Clang bug. CC @hubert.reinterpretcast @rsmith for additional opinions.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D149013/new/

https://reviews.llvm.org/D149013