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Date: Tue, 09 Nov 2010 10:37:37 +0100
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: [Qemu-devel] Re: [PATCH] add VMSTATE_BOOL
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: qemu-devel@nongnu.org

   Hi,

>> +#define VMSTATE_BOOL_ARRAY(_f, _s, _n)                               \
>> +    VMSTATE_BOOL_ARRAY_V(_f, _s, _n, 0)
>> +
>
> Why don't we pack the bits?

Point being?  As long as we don't save *big* arrays of bools it simply 
isn't worth the effort IMHO.  And for big arrays we'll probably wouldn't 
use bool in the first place ...

>> +/* bool */
>> +
>> +static int get_bool(QEMUFile *f, void *pv, size_t size)
>> +{
>> +    bool *v = pv;
>> +    *v = qemu_get_byte(f);
>> +    return 0;
>
> We must really validate that the value is 0 or 1.
> If it's not, we will get undefined behaviour.

I disagree.

You indeed have a bug in case your bool ends up with a value being 
neither 0 nor 1.  That is completely independant from savevm/loadvm 
though, it can trip you up even in case you don't save/load the VM at all.

>> +}
>> +
>> +static void put_bool(QEMUFile *f, void *pv, size_t size)
>> +{
>> +    bool *v = pv;
>> +    qemu_put_byte(f, *v);
>
> Is there a guarantee that bool is a single byte, BTW?

No.  bool must be 0 or 1 though, and a single byte is big enough to keep 
that information.

cheers,
   Gerd