On Thu, 18 Oct 2007, Ceri Davies wrote:
[ ... ]
> Hmm, you're right, I think I've misparsed the rest of the sentence
> Part of the figure is:
>
> 0x70a9add8: deadbeef deadbeef \
> 0x70a9ade0: deadbeef deadbeef +- User Data (free)
> 0x70a9ade8: deadbeef deadbeef /
> 0x70a9adf0: feedface feedface -- REDZONE
> 0x70a9adf8: 70ae3260 8440c68e -- Debugging Data
>
> Followed by the text:
>
> In the free buffers at 0x70a9add8 and 0x70a9ae28, the redzone is filled
> with 0xfeedfacefeedface. This a convenient way of determining that a
> buffer is free.
>
> I read that incorrectly; apologies for the noise.
Ok, now I see what you mean, and you're right it's not optimal.
Maybe the text should be augmented to read:
The buffers at 0x70a9add8 and 0x70a9ae28 are filled with
0xdeadbeefdeadbeef, which conveniently shows that they are free.
The buffer redzones are filled with 0xfeedfacefeedface, which
indicates they're untouched (no buffer overrun has happened).
Or similar. Now that you've given the text sample, I see where the
confusion could come in. It's indeed so that the "This is a convenient way
..." part is not quite correct because the 'buffer is free' markers are
deadbeef. Pristine redzones are an indicator of 'buffer limits were
respected', not 'buffer is free'.
If one wants to explain the marker patterns in a simple list, one could
say:
0xbaddcafe: 'buffer is allocated but uninitialized'
0xdeadbeef: 'buffer is free'
0xfeedface: 'buffer limits were respected' (no overflow)
FrankH.
>
> Ceri
> --
> That must be wonderful! I don't understand it at all.
> -- Moliere
>
