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From: "yann at droneaud dot fr" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/109863] New: RFE: more consistent flex array initialization:
 lift static storage requirement in gnu2x
Date: Mon, 15 May 2023 16:29:25 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109863

            Bug ID: 109863
           Summary: RFE: more consistent flex array initialization: lift
                    static storage requirement in gnu2x
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: yann at droneaud dot fr
  Target Milestone: ---

I've noted some discrepancies in the flex array initialization support:

    /* https://godbolt.org/z/9er5G9G15 */

    struct s { char i; char c[]; };

    extern void t(const struct s*);

    void f(void)
    {
        // ERROR: non-static initialization of a flexible array member
        const struct s c0 =3D { .c =3D "0", };
        t(&c0);

        // ERROR: non-static initialization of a flexible array member
        const struct s *const c1 =3D &(const struct s) { .c =3D "1", };
        t(c1);

        // OK
        const struct s *const c2 =3D &(constexpr struct s) { .c =3D "2", };
        t(c2);

        // ERROR: initializer element is not constant
        static const struct s *const c3 =3D &(constexpr struct s) { .c =3D =
"3", };
        t(c3);

        // OK
        static const struct s *const c4 =3D &(static constexpr struct s) { =
.c =3D
"4", };
        t(c4);
    }

AFAICT constexpr is not supposed to also mean static storage at the block
level, so flex array in c2 is initialized in a non-static way ...

Then I would be happy if GCC could be enhanced to not reject c0 and c1
initialization.

But I fear the opposite will happen, and GCC will reject c2 initialization =
too
:)=