From owner-freebsd-toolchain@freebsd.org  Wed Mar 13 12:17:07 2019
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From: Dimitry Andric <dim@FreeBSD.org>
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Subject: Re: Is this a programming error, or a compiler error..
Date: Wed, 13 Mar 2019 13:17:05 +0100
In-Reply-To: <bc4f8f4f-55c9-63ed-1ce8-b53d95a0696a@digiware.nl>
Cc: FreeBSD Toolchain <freebsd-toolchain@freebsd.org>
To: Willem Jan Withagen <wjw@digiware.nl>
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On 13 Mar 2019, at 12:57, Willem Jan Withagen <wjw@digiware.nl> wrote:
>=20
> I'm getting a crash in a Ceph test program in the following pice of =
code:
>=20
> struct entity_addrvec_t {
>   vector<entity_addr_t> v;
> .....
>   entity_addr_t legacy_addr() const {
>     for (auto& a : v) {
>       if (a.type =3D=3D entity_addr_t::TYPE_LEGACY) {
>         return a;
>       }
>     }
>     return entity_addr_t();
>   }
> ......
>=20
> Where the loop is taken, even if v.size() =3D=3D 0
> So v content is pointing to random memory and itterating over the next =
pointer results in a crash.

This can happen when the vector is invalidated, due to either it, or its
parent object having been moved from.  Maybe run this under valgrind or
AddressSanitizer, that should give some more clues.

-Dimitry


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