RE: [PATCH 5/6] plugins/loader: fix uninitialized variable warning in plugin_reset_uninstall()

[Chenqun (kuhn)]

> -----Original Message-----
> From: Philippe Mathieu-Daudé [mailto:philmd@redhat.com]
> Sent: Tuesday, November 3, 2020 10:18 AM
> To: Chenqun (kuhn) <kuhn.chenqun@huawei.com>; qemu-devel@nongnu.org;
> qemu-trivial@nongnu.org
> Cc: Alex Bennée <alex.bennee@linaro.org>; Zhanghailiang
> <zhang.zhanghailiang@huawei.com>; ganqixin <ganqixin@huawei.com>; Euler
> Robot <euler.robot@huawei.com>
> Subject: Re: [PATCH 5/6] plugins/loader: fix uninitialized variable warning in
> plugin_reset_uninstall()
> 
> On 11/3/20 2:52 AM, Chen Qun wrote:
> > After the WITH_QEMU_LOCK_GUARD macro is added, the compiler cannot
> > identify  that the statements in the macro must be executed. As a
> > result, some variables  assignment statements in the macro may be
> considered as unexecuted by the compiler.
> >
> > The compiler showed warning:
> > plugins/loader.c: In function ‘plugin_reset_uninstall’:
> > plugins/loader.c:382:15: warning: ‘ctx’ may be used uninitialized in
> > this function [-Wmaybe-uninitialized]
> 
> This shouldn't happen as the function returns before (else there is a NULL
> deref).
> 
Yes, in fact, it shouldn't have happened when the program was running.
But after added 'WITH_QEMU_LOCK_GUARD', let the compiler think it might happen.
So, we add a default value, make the compiler happy.

Thanks,
Chen Qun
> >  382 |     data->ctx = ctx;
> >      |     ~~~~~~~~~~^~~~~
> >
> > Add a default value for 'expire_time' to prevented the warning.
> >
> > Reported-by: Euler Robot <euler.robot@huawei.com>
> > Signed-off-by: Chen Qun <kuhn.chenqun@huawei.com>
> > ---
> > Cc: "Alex Bennée" <alex.bennee@linaro.org>
> > ---
> >  plugins/loader.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/plugins/loader.c b/plugins/loader.c index
> > 8ac5dbc20f..88593fe138 100644
> > --- a/plugins/loader.c
> > +++ b/plugins/loader.c
> > @@ -367,7 +367,7 @@ void plugin_reset_uninstall(qemu_plugin_id_t id,
> >                              bool reset)  {
> >      struct qemu_plugin_reset_data *data;
> > -    struct qemu_plugin_ctx *ctx;
> > +    struct qemu_plugin_ctx *ctx = NULL;
> >
> >      WITH_QEMU_LOCK_GUARD(&plugin.lock) {
> >          ctx = plugin_id_to_ctx_locked(id);
> >