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Re: [PATCH 06/10] stubdom/xenstored: Fix uninitialised variables in lu_read_state()
- To: Jürgen Groß <jgross@xxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Fri, 12 Feb 2021 17:01:25 +0000
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- Cc: Ian Jackson <iwj@xxxxxxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
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On 12/02/2021 16:08, Jürgen Groß wrote:
> On 12.02.21 16:39, Andrew Cooper wrote:
>> Various version of gcc, when compiling with -Og, complain:
>>
>> xenstored_control.c: In function ‘lu_read_state’:
>> xenstored_control.c:540:11: error: ‘state.size’ is used
>> uninitialized in this
>> function [-Werror=uninitialized]
>> if (state.size == 0)
>> ~~~~~^~~~~
>> xenstored_control.c:543:6: error: ‘state.buf’ may be used
>> uninitialized in
>> this function [-Werror=maybe-uninitialized]
>> pre = state.buf;
>> ~~~~^~~~~~~~~~~
>> xenstored_control.c:550:23: error: ‘state.buf’ may be used
>> uninitialized in
>> this function [-Werror=maybe-uninitialized]
>> (void *)head - state.buf < state.size;
>> ~~~~~^~~~
>> xenstored_control.c:550:35: error: ‘state.size’ may be used
>> uninitialized in
>> this function [-Werror=maybe-uninitialized]
>> (void *)head - state.buf < state.size;
>> ~~~~~^~~~~
>>
>> Interestingly, this is only in the stubdom build. I can't identify any
>> relevant differences vs the regular tools build.
>
> But me. :-)
>
> lu_get_dump_state() is empty for the stubdom case (this will change when
> LU is implemented for stubdom, too). In the daemon case this function is
> setting all the fields which are relevant.
So I spotted that. This instance of lu_read_state() is already within
the ifdefary, so doesn't get to see the empty stub (I think).
Also, I'd expect the compiler to complain at -O2 if it spotted that code.
>
>>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>
> Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
Thanks,
~Andrew
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