Re: [PATCH v2] hw/block: nvme: Fix a build error in nvme_get_feature()

From: "Daniel P. Berrangé" <berrange@redhat.com>
To: "Philippe Mathieu-Daudé" <philmd@redhat.com>
Cc: "Kevin Wolf" <kwolf@redhat.com>,
	"Peter Maydell" <peter.maydell@linaro.org>,
	"Thomas Huth" <thuth@redhat.com>,
	qemu-block@nongnu.org, "Bin Meng" <bin.meng@windriver.com>,
	qemu-devel@nongnu.org, "Max Reitz" <mreitz@redhat.com>,
	"Klaus Jensen" <its@irrelevant.dk>,
	"Minwoo Im" <minwoo.im.dev@gmail.com>,
	"Keith Busch" <kbusch@kernel.org>,
	"Bin Meng" <bmeng.cn@gmail.com>,
	"Alex Bennée" <alex.bennee@linaro.org>
Subject: Re: [PATCH v2] hw/block: nvme: Fix a build error in nvme_get_feature()
Date: Wed, 10 Feb 2021 11:22:19 +0000	[thread overview]
Message-ID: <20210210112219.GF1240644@redhat.com> (raw)
In-Reply-To: <efffe227-472d-698d-d8f7-cc0bbd1800c0@redhat.com>

On Wed, Feb 10, 2021 at 12:15:45PM +0100, Philippe Mathieu-Daudé wrote:
> On 2/10/21 12:12 PM, Philippe Mathieu-Daudé wrote:
> > Hi Bin,
> > 
> > On 2/10/21 11:23 AM, Bin Meng wrote:
> >> From: Bin Meng <bin.meng@windriver.com>
> >>
> >> Current QEMU HEAD nvme.c does not compile:
> >>
> >>   hw/block/nvme.c:3242:9: error: ‘result’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
> >>          trace_pci_nvme_getfeat_vwcache(result ? "enabled" : "disabled");
> >>          ^
> >>   hw/block/nvme.c:3150:14: note: ‘result’ was declared here
> >>      uint32_t result;
> >>               ^
> > 
> > Why isn't this catched by our CI? What is your host OS? Fedora 33?
> 
> Just noticed v1 and Peter's explanation:
> https://lists.gnu.org/archive/html/qemu-devel/2021-02/msg03528.html
> 
> Can you amend "default GCC 5.4 on a Ubuntu 16.04 host" information
> please?

Well Ubuntu 16.04 hasn't been considered a supported build target for
QEMU for a year now.

https://qemu.readthedocs.io/en/latest/system/build-platforms.html#linux-os-macos-freebsd-netbsd-openbsd

  "The project aims to support the most recent major version 
   at all times. Support for the previous major version will 
   be dropped 2 years after the new major version is released
   or when the vendor itself drops support, whichever comes 
   first."

IOW, we only aim for QEMU to be buildable on Ubuntu LTS 20.04 and 18.04
at this point in time.  16.04 is explicitly dropped and we will increasingly
introduce incompatibilities with it.

While this specific patch is simple, trying to keep QEMU git master
working on 16.04 is not a goal, so I'd really suggest upgrading to
a newer Ubuntu version at the soonest opportunity.

Regards,
Daniel
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