Mordante marked an inline comment as done.
Mordante added inline comments.
================
Comment at: clang/lib/Sema/SemaCast.cpp:1817-1819
+ NeedToMaterializeTemporary =
+ SrcType->isRecordType() || SrcType->isArrayType() ||
+ SrcType->isFunctionPointerType() || SrcType->isMemberPointerType();
----------------
rsmith wrote:
> It looks like GCC allowing a cast from `T*` to `T*&&` is just a bug in their
> implementation. Consider:
>
> ```
> using T = int*;
> T &&r1 = const_cast<T&&>(T{}); // GCC accepts
> T &&r2 = const_cast<T&&>(T()); // GCC rejects
> ```
>
> ... and the same behavior seems to show up for all scalar types: they permit
> `const_cast` from `T{}` but not from `T()` when `T` is `int`, `int*`, ....
> This doesn't seem like good behavior to follow. I think we should either
> implement the current direction of 1965 (that is, only allow classes and
> arrays here) or leave the current behavior (following the standard as-is)
> alone.
> It looks like GCC allowing a cast from `T*` to `T*&&` is just a bug in their
> implementation. Consider:
>
> ```
> using T = int*;
> T &&r1 = const_cast<T&&>(T{}); // GCC accepts
> T &&r2 = const_cast<T&&>(T()); // GCC rejects
> ```
>
> ... and the same behavior seems to show up for all scalar types: they permit
> `const_cast` from `T{}` but not from `T()` when `T` is `int`, `int*`, ....
Interesting I hadn't test with `T()` only with `T{}`
> This doesn't seem like good behavior to follow.
Agreed.
> I think we should either implement the current direction of 1965 (that is,
> only allow classes and arrays here)
I'll then limit the patch to array types (next to the already allowed record
types.
> or leave the current behavior (following the standard as-is) alone.
Now I'm somewhat confused, because I thought arrays are allowed in the standard
http://eel.is/c++draft/expr.const.cast#3 as introduced by N4261.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D87565/new/
https://reviews.llvm.org/D87565
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