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From: Gerd Hoffmann <kraxel@redhat.com>
Date: Mon, 17 Jul 2017 16:16:37 +0200
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Subject: Re: [Qemu-devel] Hacks for building on gcc 7 / Fedora 26
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To: Eric Blake <eblake@redhat.com>, Philippe =?ISO-8859-1?Q?Mathieu-Daud=E9?= <f4bug@amsat.org>, "Dr. David Alan
	Gilbert" <dgilbert@redhat.com>, qemu-devel@nongnu.org

  Hi,

> FWIW, most of these have been fixed in the meantime; the only
> remaining
> hack I had to add was:
>=20
> diff --git i/hw/usb/bus.c w/hw/usb/bus.c
> index 5939b273b9..bce011058b 100644
> --- i/hw/usb/bus.c
> +++ w/hw/usb/bus.c
> @@ -407,8 +407,9 @@ void usb_register_companion(const char
> *masterbus,
> USBPort *ports[],
> =C2=A0void usb_port_location(USBPort *downstream, USBPort *upstream, in=
t
> portnr)
> =C2=A0{
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (upstream) {
> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0snprintf(downstream->p=
ath, sizeof(downstream->path),
> "%s.%d",
> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0upstream->path, portnr);
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0int l =3D snprintf(dow=
nstream->path, sizeof(downstream->path),
> "%s.%d",
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0upstream->path, portnr);
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0assert(l < sizeof(down=
stream->path));

Approach looks ok to me.

Maximum hub chain length is 5, number of ports hubs is limited too,
you'll never need more that two digits for port numbers.  So 2*5 plus 4
connecting dots =3D> 14 chars is the max strlen.  path size is 16, so it
will fit, including the terminating \0.

Trying things like "assert(portnr <=3D 99)" have no effect on the
possible string length calculated by gcc7.

cheers,
  Gerd