[PATCH 2/3] storage.dll16: Correctly handle block values of -1.

[Zebediah Figura]

On 02/20/2017 08:23 AM, Zebediah Figura wrote:
> On 02/20/2017 03:39 AM, Alexandre Julliard wrote:
>> Zebediah Figura <z.figura12 at gmail.com> writes:
>>
>>> @@ -610,9 +610,10 @@ STORAGE_get_nth_next_small_blocknr(stream_access16*str,int blocknr,int nr) {
>>>  	READ_HEADER(str);
>>>  	assert(blocknr>=0);
>>>  	while ((nr--) && (blocknr>=0)) {
>>> -		if (lastblocknr/128!=blocknr/128) {
>>> +		if (lastblocknr>>7 != blocknr>>7)
>>> +		{
>>>  			int	bigblocknr;
>>> -			bigblocknr = STORAGE_get_nth_next_big_blocknr(str,sth.sbd_startblock,blocknr/128);
>>> +			bigblocknr = STORAGE_get_nth_next_big_blocknr(str,sth.sbd_startblock,blocknr>>7);
>>
>>
>> I'm not sure what you are trying to fix. Most places already check that
>> blocknr is >= 0, and if it's really negative, you can't rely on right
>> shift doing the right thing.
>>
> 
> Without the patch, I get failed assertions in several places that the
> blocknr is >= 0. With it, it seems to pass that -1 on to the program,
> causing it not to crash. This might be fixing the symptom rather than
> the cause, though.
> 
> 
> 

My apologies. To be more accurate, the game crashes because this
function is passed blocknr=12, nr=1, so when the loop is executed,
lastblocknr/128 == blocknr/128 == 0, so the assertion "lastblocknr >= 0"
fails. If there is a better way to fix this, I do not know what it is.