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Re: [Qemu-devel] [PATCH 23/25] fdc: Move floppy geometry guessing back f
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCH 23/25] fdc: Move floppy geometry guessing back from block.c |
Date: |
Tue, 10 Jul 2012 09:41:27 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0 |
Am 09.07.2012 19:01, schrieb Anthony Liguori:
> On 07/09/2012 11:46 AM, Eric Blake wrote:
>> On 07/09/2012 10:07 AM, Markus Armbruster wrote:
>>
>>>>> This is an unconditional use of fd_type[0]. If floppy == NULL, this is
>>>>> dereferencing an uninitialized value.
>>>>>
>>>>> I'm not sure why the explicit initialization was removed...
>>>
>>> Brain fart on my part, sorry. The old loop assigns only if the drive
>>> exists. The new loop assigns unconditionally. Except the whole loop is
>>> still conditional.
>>>
>>> Testing can't flag this, because floppy is never null.
>>>
>>>> Looks broken indeed. I just wonder why my gcc (or the buildbots) didn't
>>>> complain.
>>>
>>> Me too. Looks like I should upgrade to a more recent gcc.
>>
>> It's probably not the version of the gcc you used, but whether or not
>> your CFLAGS include -O2. Gcc has the (IMO very annoying) limitation
>> that uninitialized-use analysis can only be performed if you are also
>> doing optimization. You have to use a tool like clang or Coverity if
>> you want more reliable uninitialized-use analysis even while building
>> -O0 debug images.
>>
>
> Specifically, without -O, GCC doesn't do data flow analysis so any warning
> that
> requires DFA won't get triggered.
>
> So in general, if you are normally building with -O0, make sure to also build
> with -O in order to get full warnings.
Just checked it to be sure, this doesn't seem to be the reason:
CFLAGS=-O2 -D_FORTIFY_SOURCE=2 -g
Kevin
- [Qemu-devel] [PATCH 24/25] qtest: Tidy up temporary files properly, (continued)
- [Qemu-devel] [PATCH 24/25] qtest: Tidy up temporary files properly, Kevin Wolf, 2012/07/09
- [Qemu-devel] [PATCH 21/25] fdc_test: introduce test_sense_interrupt, Kevin Wolf, 2012/07/09
- [Qemu-devel] [PATCH 19/25] fdc: fix interrupt handling, Kevin Wolf, 2012/07/09
- [Qemu-devel] [PATCH 23/25] fdc: Move floppy geometry guessing back from block.c, Kevin Wolf, 2012/07/09
- Re: [Qemu-devel] [PATCH 23/25] fdc: Move floppy geometry guessing back from block.c, Anthony Liguori, 2012/07/09
- Re: [Qemu-devel] [PATCH 23/25] fdc: Move floppy geometry guessing back from block.c, Kevin Wolf, 2012/07/09
- Re: [Qemu-devel] [PATCH 23/25] fdc: Move floppy geometry guessing back from block.c, Anthony Liguori, 2012/07/09
- Re: [Qemu-devel] [PATCH 23/25] fdc: Move floppy geometry guessing back from block.c, Markus Armbruster, 2012/07/09
- Re: [Qemu-devel] [PATCH 23/25] fdc: Move floppy geometry guessing back from block.c, Eric Blake, 2012/07/09
- Re: [Qemu-devel] [PATCH 23/25] fdc: Move floppy geometry guessing back from block.c, Anthony Liguori, 2012/07/09
- Re: [Qemu-devel] [PATCH 23/25] fdc: Move floppy geometry guessing back from block.c,
Kevin Wolf <=
[Qemu-devel] [PATCH 22/25] fdc: Drop broken code for user-defined floppy geometry, Kevin Wolf, 2012/07/09
[Qemu-devel] [PATCH 25/25] block: Factor bdrv_read_unthrottled() out of guess_disk_lchs(), Kevin Wolf, 2012/07/09
Re: [Qemu-devel] [PULL 00/25] Block patches, Anthony Liguori, 2012/07/09