Date: Fri, 26 Apr 2019 08:32:55 +0000 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Alan Somers <asomers@freebsd.org> Cc: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: buf(9) woes: when does bcopy do nothing at all? Message-ID: <23438.1556267575@critter.freebsd.dk> In-Reply-To: <CAOtMX2gdw%2BeQQU_-DC%2BEgimbCyw6ynbX1haGLUmn1dApk4rMZw@mail.gmail.com> References: <CAOtMX2gdw%2BeQQU_-DC%2BEgimbCyw6ynbX1haGLUmn1dApk4rMZw@mail.gmail.com>
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In message <CAOtMX2gdw+eQQU_-DC+EgimbCyw6ynbX1haGLUmn1dApk4rMZw@mail.gmail=
.com>, Alan Somers writes:
>How is it possible that bcopy() doesn't affect its output array at all?
That conclusion does not follow from your example:
>bcopy(cp, iov->iov_base, cnt);
>r =3D memcmp(cp, iov->iov_base, cnt);
>if (r)
> printf("uiomove: miscompare\n");
If [cp:cp+cnt] and [iov_base:iov_base+cnt] overlap the bcopy result
is undefined.
Try memmove instead ?
-- =
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe =
Never attribute to malice what can adequately be explained by incompetence=
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