[Bug c++/98675] Accessing member of temporary outside its lifetime allowed in constexpr function

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98675

--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Jason Merrill <jason@gcc.gnu.org>:

https://gcc.gnu.org/g:9fdbd7d6fa5e0a76898dd66658934e3184111680

commit r14-2773-g9fdbd7d6fa5e0a76898dd66658934e3184111680
Author: Nathaniel Shead <nathanieloshead@gmail.com>
Date:   Sun Jul 23 01:15:14 2023 +1000

    c++: Track lifetimes in constant evaluation [PR70331,PR96630,PR98675]

    This adds rudimentary lifetime tracking in C++ constexpr contexts,
    allowing the compiler to report errors with using values after their
    backing has gone out of scope. We don't yet handle other ways of
    accessing values outside their lifetime (e.g. following explicit
    destructor calls).

            PR c++/96630
            PR c++/98675
            PR c++/70331

    gcc/cp/ChangeLog:

            * constexpr.cc (constexpr_global_ctx::is_outside_lifetime): New
            function.
            (constexpr_global_ctx::get_value): Don't return expired values.
            (constexpr_global_ctx::get_value_ptr): Likewise.
            (constexpr_global_ctx::remove_value): Mark value outside
            lifetime.
            (outside_lifetime_error): New function.
            (cxx_eval_call_expression): No longer track save_exprs.
            (cxx_eval_loop_expr): Likewise.
            (cxx_eval_constant_expression): Add checks for outside lifetime
            values. Remove local variables at end of bind exprs, and
            temporaries after cleanup points.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp1y/constexpr-lifetime1.C: New test.
            * g++.dg/cpp1y/constexpr-lifetime2.C: New test.
            * g++.dg/cpp1y/constexpr-lifetime3.C: New test.
            * g++.dg/cpp1y/constexpr-lifetime4.C: New test.
            * g++.dg/cpp1y/constexpr-lifetime5.C: New test.
            * g++.dg/cpp1y/constexpr-lifetime6.C: New test.

    Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>