Confusing or confused code
Adam Jackson
ajax at nwnk.net
Mon Mar 15 11:52:08 PDT 2010
On Thu, 2010-03-11 at 12:59 +0100, Michael Thayer wrote:
> Hello,
>
> I suspect that this code:
>
> http://cgit.freedesktop.org/xorg/xserver/tree/hw/xfree86/common/xf86Mode.c?id=326429badfc76885e4652ddc72860810c0e8d102#n1300
>
> until line 1313 is supposed to be freeing the old list at
> scrp->clockRanges, duplicating the user supplied list and storing it
> there. If that is right, then it looks to me though like it will not
> work unless scrp->clockRanges is initially NULL
AFAICT yes; if ->clockRanges is not initially NULL, then we will not
store the duplicated list there. Which seems goofy.
> and the user only supplies a list with a single element.
In that, after the first memcpy, storeClockRanges->next and cp->next
will point to the same place, so subsequent copies will just be lost in
space, yeah.
> Did I miss something important there?
I think your analysis is right, that code's garbage.
At least in the case of virtual drivers like vboxvideo, I think we
should reasonably allow you to just pass in NULL for clockRanges. But
it's trivial to set up just one range that's sufficient to cover
everything. Gross, but sufficient.
- ajax
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