Am 12.03.19 um 18:34 schrieb Eric Anholt:
> Ilia Mirkin <imir...@alum.mit.edu> writes:
>
>> I believe the distinction here is between initializing all the fields
>> and using them individually (thus leaving the padding uninitialized),
>> vs using the fields to create a structure to hash as a sequence of
>> bytes. For the latter, you really need all the memory initialized, not
>> just the "valid" parts of the structure. In at least my mind, it's
>> fairly well-established that compilers don't always initialize all of
>> a structure's underlying bytes, but I also don't have a specific
>> instance of that situation I can point to.
>>
>> For most usage, foo = {0} is fine since you're not hashing the bytes
>> but rather accessing the fields directly. But for hashing, you really
>> want all the bits initialized.
>
> Gah. The commit message even said it was about padding, and I failed to
> read. Sorry for the noise, this does seem right.
The alternative is to use explicit padding in the struct, so that
structure initialization is guaranteed to initialize everything to zero.
I believe some places still do that too, but it's not very nice neither
(can easily make mistakes there). So - pick your poison...
Roland
>
>
> _______________________________________________
> mesa-dev mailing list
> mesa-dev@lists.freedesktop.org
> https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.freedesktop.org%2Fmailman%2Flistinfo%2Fmesa-dev&data=02%7C01%7Csroland%40vmware.com%7Cd6e706866d844beb84a808d6a7110f53%7Cb39138ca3cee4b4aa4d6cd83d9dd62f0%7C0%7C0%7C636880089068822714&sdata=AENcqpYCV4d4DJW3q4Bkg9GXIEyU6Au8Yccuthd7Mbk%3D&reserved=0
>
_______________________________________________
mesa-dev mailing list
mesa-dev@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/mesa-dev
