[Bug c++/102201] New: Accepts invalid C++98 with nested class and sizeof of outer's non-static field

[Bug c++/102201] New: Accepts invalid C++98 with nested class and sizeof of outer's non-static field

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102201

            Bug ID: 102201
           Summary: Accepts invalid C++98 with nested class and sizeof of
                    outer's non-static field
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: accepts-invalid
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take:
struct outer {
    struct inner {
         inner() :x(sizeof(y)) { }
        unsigned int x;
    };
    int y;
};

----- CUT ----
The above code is valid C++11 but invalid C++98 because the field y is
non-static.

[Bug c++/102201] Accepts invalid C++98 with nested class and sizeof of outer's non-static field

[harald at gigawatt dot nl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102201

Harald van Dijk <harald at gigawatt dot nl> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |harald at gigawatt dot nl

--- Comment #1 from Harald van Dijk <harald at gigawatt dot nl> ---
This doesn't need inner classes, a simpler reproducer is:

struct S { int i; };
int j = sizeof S::i;

gcc accepts this in all modes ever since the C++11 rule for non-static members
in unevaluated contexts was implemented (4.4). clang says in C++98 mode:

test.cc:2:19: error: invalid use of non-static data member 'i'
int j = sizeof S::i;
               ~~~^
1 error generated.

[Bug c++/102201] Accepts invalid C++98 with nested class and sizeof of outer's non-static field

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102201

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
It's accepted since:

    C++ DR 613

            C++ DR 613
            * semantics.c (finish_non_static_data_member): Allow such
references
            without an associated object in sizeof/decltype/alignof.

    From-SVN: r145375

(and SVN r145620 on the gcc-4.4 branch).

Presumably treating it as a DR was intentional.

[Bug c++/102201] Accepts invalid C++98 with nested class and sizeof of outer's non-static field

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102201

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |WONTFIX
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
DR613 is CD1 so yes it is included in C++98/C++03.  clang must have decided
CD1's are not included ...

[Bug c++/102201] Accepts invalid C++98 with nested class and sizeof of outer's non-static field

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102201

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
CD1 was a C++0x draft:

"CD1: A DR issue not resolved in TC1 but included in Committee Draft 1. CD1 was
advanced for balloting at the September, 2008 WG21 meeting."

DR 613 was resolved by N2253, which was a post-C++03 change, and wasn't adopted
as a defect report. So arguably Clang is right to reject it in C++03 mode.

We could make it a pedwarn, but I think WONTFIX is probably right. There seems
to be no advantage to rejecting it (strictly conforming C++98 programs aren't
going to be using SFINAE tricks that could detect this).