Re: [PATCH v2] block-qdict: Fix -Werror=maybe-uninitialized build failure

[Markus Armbruster <armbru@redhat.com>]

Murilo Opsfelder Araujo <muriloo@linux.ibm.com> writes:

> Building QEMU on Fedora 37 (Rawhide Prerelease) ppc64le failed with the
> following error:
>
>     $ ../configure --prefix=/usr/local/qemu-disabletcg --target-list=ppc-softmmu,ppc64-softmmu --disable-tcg --disable-linux-user
>     ...
>     $ make -j$(nproc)
>     ...
>     FAILED: libqemuutil.a.p/qobject_block-qdict.c.o
>     cc -m64 -mlittle-endian -Ilibqemuutil.a.p -I. -I.. -Isubprojects/libvhost-user -I../subprojects/libvhost-user -Iqapi -Itrace -Iui -Iui/shader -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -I/usr/include/sysprof-4 -I/usr/include/lib
>     mount -I/usr/include/blkid -I/usr/include/gio-unix-2.0 -I/usr/include/p11-kit-1 -I/usr/include/pixman-1 -fdiagnostics-color=auto -Wall -Winvalid-pch -Werror -std=gnu11 -O2 -g -isystem /root/qemu/linux-headers -isystem linux-headers -iquote
>      . -iquote /root/qemu -iquote /root/qemu/include -iquote /root/qemu/disas/libvixl -pthread -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -Wstrict-prototypes -Wredundant-decls -Wundef -Wwrite
>     -strings -Wmissing-prototypes -fno-strict-aliasing -fno-common -fwrapv -Wold-style-declaration -Wold-style-definition -Wtype-limits -Wformat-security -Wformat-y2k -Winit-self -Wignored-qualifiers -Wempty-body -Wnested-externs -Wendif-label
>     s -Wexpansion-to-defined -Wimplicit-fallthrough=2 -Wno-missing-include-dirs -Wno-shift-negative-value -Wno-psabi -fstack-protector-strong -fPIE -MD -MQ libqemuutil.a.p/qobject_block-qdict.c.o -MF libqemuutil.a.p/qobject_block-qdict.c.o.d -
>     o libqemuutil.a.p/qobject_block-qdict.c.o -c ../qobject/block-qdict.c
>     In file included from /root/qemu/include/qapi/qmp/qdict.h:16,
>                      from /root/qemu/include/block/qdict.h:13,
>                      from ../qobject/block-qdict.c:11:
>     /root/qemu/include/qapi/qmp/qobject.h: In function ‘qdict_array_split’:
>     /root/qemu/include/qapi/qmp/qobject.h:49:17: error: ‘subqdict’ may be used uninitialized [-Werror=maybe-uninitialized]
>        49 |     typeof(obj) _obj = (obj);                                   \
>           |                 ^~~~
>     ../qobject/block-qdict.c:227:16: note: ‘subqdict’ declared here
>       227 |         QDict *subqdict;
>           |                ^~~~~~~~
>     cc1: all warnings being treated as errors
>
> Fix build failure by expanding the ternary operation.
> Tested with `make check-unit` (the check-block-qdict test passed).
>
> Signed-off-by: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>
> Cc: Kevin Wolf <kwolf@redhat.com>
> Cc: Hanna Reitz <hreitz@redhat.com>
> Cc: Markus Armbruster <armbru@redhat.com>
> ---
> v1: https://lists.nongnu.org/archive/html/qemu-devel/2022-03/msg03224.html
>
>  qobject/block-qdict.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/qobject/block-qdict.c b/qobject/block-qdict.c
> index 1487cc5dd8..4a83bda2c3 100644
> --- a/qobject/block-qdict.c
> +++ b/qobject/block-qdict.c
> @@ -251,12 +251,12 @@ void qdict_array_split(QDict *src, QList **dst)
>          if (is_subqdict) {
>              qdict_extract_subqdict(src, &subqdict, prefix);
>              assert(qdict_size(subqdict) > 0);
> +            qlist_append_obj(*dst, QOBJECT(subqdict));
>          } else {
>              qobject_ref(subqobj);
>              qdict_del(src, indexstr);
> +            qlist_append_obj(*dst, subqobj);
>          }
> -
> -        qlist_append_obj(*dst, subqobj ?: QOBJECT(subqdict));
>      }
>  }

Reviewed-by: Markus Armbruster <armbru@redhat.com>