Comment 3 for bug 856731

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On 9/23/2011 9:23 AM, Martin Pool wrote:
> Hi Adi,
>
> Thanks for the report.
>
> Please attach the traceback from ~/.bzr.log and if possible the run
> with -Dmem_dump.
>
> istr seeing something like this being due to a unix api quirk
> rather than actually being out of memory.
>
> ** Changed in: bzr Importance: Undecided => Medium
>
> ** Changed in: bzr Status: New => Incomplete
>
> ** Tags added: aix memory
>

If it is AIX, my guess is that we are missing a place where
"malloc(0)" returns NULL rather than a pointer like a lot of GNU based
systems. I know we had to fix up some patience-diff code for that case.

Given the traceback, I'm suspecting the create_delta_index_from_delta
code.

Specifically:
max_num_entries = (src->size - 1) / RABIN_WINDOW;

/* allocate an array to hold whatever entries we find */
entries = malloc(sizeof(*entry) * max_num_entries);
if (!entries) /* malloc failure */
    return DELTA_OUT_OF_MEMORY;

If src->size is less than 17, then that ends up as (16-1) / 16 = 0.
The algorithm still works today, because all the rest of the code just
skips, and doesn't try to assign anything into the entries list.
However, we could just do:

if (max_num_entries == 0) {
  *fresh = old_index;
  return DELTA_OK;
}

John
=:->
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