[Bug c++/97328] [10 Regression] ICE in verify_ctor_sanity, at cp/constexpr.c:3995 since r10-7313-gb599bf9d6d1e180d

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97328

--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:8094f781c35b64da68245d351b85546cca5b809b

commit r10-8938-g8094f781c35b64da68245d351b85546cca5b809b
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu Oct 22 07:40:40 2020 -0400

    c++: Handle RANGE_EXPR index in init_subob_ctx [PR97328]

    In the testcase below, we're ICEing during constexpr evaluation of the
    CONSTRUCTOR {.data={{}, [1 ... 7]={}}} of type 'vector'.  The interesting
    thing about this CONSTRUCTOR is that it has a RANGE_EXPR index for an
    element initializer which doesn't satisfy reduced_constant_expression_p
    (because the field 't' is uninitialized).

    This is a problem because init_subob_ctx currently punts on setting up a
    sub-aggregate initialization context when given a RANGE_EXPR index, so
    we later trip over the asserts in verify_ctor_sanity when recursing into
    cxx_eval_bare_aggregate on this element initializer.

    Fix this by making init_subob_ctx set up an appropriate initialization
    context when supplied a RANGE_EXPR index.

    gcc/cp/ChangeLog:

            PR c++/97328
            * constexpr.c (init_subob_ctx): Don't punt on RANGE_EXPR
            indexes, instead build a sub-aggregate initialization context
            with no subobject.

    gcc/testsuite/ChangeLog:

            PR c++/97328
            * g++.dg/cpp2a/constexpr-init19.C: New test.
            * g++.dg/cpp2a/constexpr-init20.C: New test.

    (cherry picked from commit 3d423c6f6a69d87ad52ba3af75f3debd8a8b8810)