cor3ntin 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}}
----------------
aaron.ballman wrote:
> 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.
I believe this is fine, or at least i can't find any wording that would say
it's not.
In particular:
- taking the address of &b is fine
- adding + 1 to it is fine: http://eel.is/c++draft/expr#add-4.2
- casting it to a pointer to base is fine http://eel.is/c++draft/conv.ptr#3
- treating the whole expression as a constant expression is also fine
http://eel.is/c++draft/expr.const#13.3
So i do believe GCC, MSVC and ICC are correct here.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D149013/new/
https://reviews.llvm.org/D149013
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