On 11/29/16 17:29, Michael S. Tsirkin wrote:
> On Mon, Nov 28, 2016 at 08:57:01PM +0100, Laszlo Ersek wrote:
>> According to ISO C99 / N1256 (referenced in HACKING):
>>
>>> 6.5.8 Relational operators
>>>
>>> 4 For the purposes of these operators, a pointer to an object that is
>>> not an element of an array behaves the same as a pointer to the first
>>> element of an array of length one with the type of the object as its
>>> element type.
>>>
>>> 5 When two pointers are compared, the result depends on the relative
>>> locations in the address space of the objects pointed to. If two
>>> pointers to object or incomplete types both point to the same object,
>>> or both point one past the last element of the same array object, they
>>> compare equal. If the objects pointed to are members of the same
>>> aggregate object, pointers to structure members declared later compare
>>> greater than pointers to members declared earlier in the structure,
>>> and pointers to array elements with larger subscript values compare
>>> greater than pointers to elements of the same array with lower
>>> subscript values. All pointers to members of the same union object
>>> compare equal. If the expression /P/ points to an element of an array
>>> object and the expression /Q/ points to the last element of the same
>>> array object, the pointer expression /Q+1/ compares greater than /P/.
>>> In all other cases, the behavior is undefined.
>>
>> Our AddressSpace objects are allocated generally individually, and kept in
>> the "address_spaces" linked list, so we mustn't compare their addresses
>> with relops.
>>
>> Convert the pointers subjected to the relop in rom_order_compare() to
>> "uintptr_t":
>>
>>> 7.18.1.4 Integer types capable of holding object pointers
>>>
>>> 1 [...]
>>>
>>> The following type designates an unsigned integer type with the
>>> property that any valid pointer to void can be converted to this type,
>>> then converted back to pointer to void, and the result will compare
>>> equal to the original pointer:
>>>
>>> /uintptr_t/
>>>
>>> These types are optional.
>>
>> Cc: "Michael S. Tsirkin" <m...@redhat.com>
>> Cc: Alistair Francis <alistair.fran...@xilinx.com>
>> Cc: Paolo Bonzini <pbonz...@redhat.com>
>> Cc: Peter Maydell <peter.mayd...@linaro.org>
>> Cc: qemu-devel@nongnu.org
>> Fixes: 3e76099aacb4dae0d37ebf95305369e03d1491e6
>> Signed-off-by: Laszlo Ersek <ler...@redhat.com>
>> ---
>> hw/core/loader.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/hw/core/loader.c b/hw/core/loader.c
>> index c0d645a87134..766e48f2aec2 100644
>> --- a/hw/core/loader.c
>> +++ b/hw/core/loader.c
>> @@ -818,7 +818,7 @@ static QTAILQ_HEAD(, Rom) roms =
>> QTAILQ_HEAD_INITIALIZER(roms);
>>
>> static inline bool rom_order_compare(Rom *rom, Rom *item)
>> {
>> - return (rom->as > item->as) ||
>> + return ((uintptr_t)(void*)rom->as > (uintptr_t)(void*)item->as) ||
>> (rom->as == item->as && rom->addr >= item->addr);
>> }
>
> Can't hurt but why cast to void *?
> Should not be needed.
Just to comply with the word of the standard above; it says "any valid
pointer to void".
>
>> --
>> 2.9.2
