[Qemu-devel] [PATCH] block/vpc: fix uninitialised variable compiler warning

[Qemu-devel] [PATCH] block/vpc: fix uninitialised variable compiler warning

[Mark Cave-Ayland]

Since commit cfc87e00 "block/vpc.c: Handle write failures in
get_image_offset()" older versions of gcc (in this case 4.7) incorrectly
warn that "ret" can be used uninitialised in vpc_co_pwritev().

Setting ret to 0 at the start of vpc_co_pwritev() prevents the warning
in gcc 4.7 and enables compilation with -Werror to succeed.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
---
 block/vpc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/vpc.c b/block/vpc.c
index 10e6519..574879b 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -649,7 +649,7 @@ vpc_co_pwritev(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
     int64_t image_offset;
     int64_t n_bytes;
     int64_t bytes_done = 0;
-    int ret;
+    int ret = 0;
     VHDFooter *footer =  (VHDFooter *) s->footer_buf;
     QEMUIOVector local_qiov;
 
-- 
1.7.10.4

Re: [Qemu-devel] [PATCH] block/vpc: fix uninitialised variable compiler warning

[Eric Blake]

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On 07/21/2017 03:21 AM, Mark Cave-Ayland wrote:
> Since commit cfc87e00 "block/vpc.c: Handle write failures in
> get_image_offset()" older versions of gcc (in this case 4.7) incorrectly
> warn that "ret" can be used uninitialised in vpc_co_pwritev().
> 
> Setting ret to 0 at the start of vpc_co_pwritev() prevents the warning
> in gcc 4.7 and enables compilation with -Werror to succeed.
> 
> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> ---
>  block/vpc.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 

Reviewed-by: Eric Blake <eblake@redhat.com>

> diff --git a/block/vpc.c b/block/vpc.c
> index 10e6519..574879b 100644
> --- a/block/vpc.c
> +++ b/block/vpc.c
> @@ -649,7 +649,7 @@ vpc_co_pwritev(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
>      int64_t image_offset;
>      int64_t n_bytes;
>      int64_t bytes_done = 0;
> -    int ret;
> +    int ret = 0;
>      VHDFooter *footer =  (VHDFooter *) s->footer_buf;
>      QEMUIOVector local_qiov;
>  
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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Re: [Qemu-devel] [PATCH] block/vpc: fix uninitialised variable compiler warning

[Stefan Hajnoczi]

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On Fri, Jul 21, 2017 at 09:21:05AM +0100, Mark Cave-Ayland wrote:
> Since commit cfc87e00 "block/vpc.c: Handle write failures in
> get_image_offset()" older versions of gcc (in this case 4.7) incorrectly
> warn that "ret" can be used uninitialised in vpc_co_pwritev().
> 
> Setting ret to 0 at the start of vpc_co_pwritev() prevents the warning
> in gcc 4.7 and enables compilation with -Werror to succeed.
> 
> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> ---
>  block/vpc.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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Re: [Qemu-devel] [PATCH] block/vpc: fix uninitialised variable compiler warning

[Peter Maydell]

On 21 July 2017 at 09:21, Mark Cave-Ayland
<mark.cave-ayland@ilande.co.uk> wrote:
> Since commit cfc87e00 "block/vpc.c: Handle write failures in
> get_image_offset()" older versions of gcc (in this case 4.7) incorrectly
> warn that "ret" can be used uninitialised in vpc_co_pwritev().
>
> Setting ret to 0 at the start of vpc_co_pwritev() prevents the warning
> in gcc 4.7 and enables compilation with -Werror to succeed.
>
> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> ---
>  block/vpc.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/block/vpc.c b/block/vpc.c
> index 10e6519..574879b 100644
> --- a/block/vpc.c
> +++ b/block/vpc.c
> @@ -649,7 +649,7 @@ vpc_co_pwritev(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
>      int64_t image_offset;
>      int64_t n_bytes;
>      int64_t bytes_done = 0;
> -    int ret;
> +    int ret = 0;
>      VHDFooter *footer =  (VHDFooter *) s->footer_buf;
>      QEMUIOVector local_qiov;
>

Thanks; applied to master as a buildfix.

-- PMM

Re: [Qemu-devel] [PATCH] block/vpc: fix uninitialised variable compiler warning

[no-reply]

Hi,

This series failed automatic build test. Please find the testing commands and
their output below. If you have docker installed, you can probably reproduce it
locally.

Type: series
Subject: [Qemu-devel] [PATCH] block/vpc: fix uninitialised variable compiler warning
Message-id: 1500625265-23844-1-git-send-email-mark.cave-ayland@ilande.co.uk

=== TEST SCRIPT BEGIN ===
#!/bin/bash
set -e
git submodule update --init dtc
# Let docker tests dump environment info
export SHOW_ENV=1
export J=8
time make docker-test-quick@centos6
time make docker-test-build@min-glib
time make docker-test-mingw@fedora
=== TEST SCRIPT END ===

Updating 3c8cf5a9c21ff8782164d1def7f44bd888713384
Switched to a new branch 'test'
3a33f06 block/vpc: fix uninitialised variable compiler warning

=== OUTPUT BEGIN ===
Submodule 'dtc' (git://git.qemu-project.org/dtc.git) registered for path 'dtc'
Cloning into '/var/tmp/patchew-tester-tmp-q6lf38_m/src/dtc'...
Submodule path 'dtc': checked out '558cd81bdd432769b59bff01240c44f82cfb1a9d'
  BUILD   centos6
make[1]: Entering directory '/var/tmp/patchew-tester-tmp-q6lf38_m/src'
  ARCHIVE qemu.tgz
  ARCHIVE dtc.tgz
  COPY    RUNNER
    RUN test-quick in qemu:centos6 
/usr/bin/docker-current: Error response from daemon: containerd: container did not start before the specified timeout.
Traceback (most recent call last):
  File "./tests/docker/docker.py", line 382, in <module>
    sys.exit(main())
  File "./tests/docker/docker.py", line 379, in main
    return args.cmdobj.run(args, argv)
  File "./tests/docker/docker.py", line 237, in run
    return Docker().run(argv, args.keep, quiet=args.quiet)
  File "./tests/docker/docker.py", line 205, in run
    quiet=quiet)
  File "./tests/docker/docker.py", line 123, in _do_check
    return subprocess.check_call(self._command + cmd, **kwargs)
  File "/usr/lib64/python2.7/subprocess.py", line 186, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['docker', 'run', '--label', 'com.qemu.instance.uuid=1251217872ca11e79333525400c803e1', '-u', '0', '-t', '--rm', '--net=none', '-e', 'TARGET_LIST=', '-e', 'EXTRA_CONFIGURE_OPTS=', '-e', 'V=', '-e', 'J=8', '-e', 'DEBUG=', '-e', 'SHOW_ENV=1', '-e', 'CCACHE_DIR=/var/tmp/ccache', '-v', '/var/tmp/patchew-tester-tmp-q6lf38_m/src/docker-src.2017-07-27-08.49.43.1505:/var/tmp/qemu:z,ro', '-v', '/root/.cache/qemu-docker-ccache:/var/tmp/ccache:z', 'qemu:centos6', '/var/tmp/qemu/run', 'test-quick']' returned non-zero exit status 125
tests/docker/Makefile.include:136: recipe for target 'docker-run' failed
make[1]: *** [docker-run] Error 1
make[1]: Leaving directory '/var/tmp/patchew-tester-tmp-q6lf38_m/src'
tests/docker/Makefile.include:168: recipe for target 'docker-run-test-quick@centos6' failed
make: *** [docker-run-test-quick@centos6] Error 2
=== OUTPUT END ===

Test command exited with code: 2


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