[Bug c++/93169] [10 regression] Variable incorrectly put into readonly section.

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93169

--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:8f9dd1b0bdd935592ba151e9d843fddf6193afbc

commit r10-6749-g8f9dd1b0bdd935592ba151e9d843fddf6193afbc
Author: Marek Polacek <polacek@redhat.com>
Date:   Wed Feb 19 16:36:38 2020 -0500

    c++: Fix wrong-code with non-constexpr constructor [PR93169]

    In order to detect modifying constant objects in constexpr evaluation,
    which is UB, in r10-2655 I added code that sets TREE_READONLY on
    CONSTRUCTORs of const-qualified objects after they have been fully
    constructed.  But I never made sure that what we're setting the flag
    on actually is a CONSTRUCTOR.  Consequently, as this test case shows,
    we could set TREE_READONLY on a VAR_DECL that in fact wasn't constant,
    causing problems later.  Fixed by setting the flag on CONSTRUCTORs
    only, and only when the evaluation produced something constant.

    2020-02-19  Marek Polacek  <polacek@redhat.com>

        PR c++/93169 - wrong-code with a non-constexpr constructor.
        * constexpr.c (cxx_eval_call_expression): Only set TREE_READONLY
        on constant CONSTRUCTORs.

        * g++.dg/cpp0x/constexpr-93169.C: New test.