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c22b6124e2
Problem : Dereference of null pointer @ 4199.
Diagnostic : False positive.
Rationale : Suggested error path implies that newlen == 0 and
newlen > hislen, which implies hislen < 0, which is
impossible (hislen is always between 0 and 10000).
Resolution : Refactor code.
Asserting oldlen >= 0 should have sufficed, but
for some reason analyzer doesn't follow implications in
that case.
Asserting newlen != 0 || newlen <= hislen works.
But the chance has been taken to do extensive
refactoring of this function, as it was difficult to
understand as it was.
As a result of refactoring, assert is not needed anymore,
as we don't call clear_hist_entry() in refactored version.
Refactor : - Rework algorithm:
* Drop guard for OOM case, which can't happen now.
* Drop empty/growing/shrinking cases. Simplify to always
doing the same.
* Perform circular array reordering in all cases
(before, it only did when shrinking).
* Work in batches through memcpy/memset, instead of one
entry at a time, as it did before.
- Inline variable declarations.
- Replace `ssize_t` by `int`.
- Introduce oldlen as entry value of hislen.
- Add a lot of comments.
Helped-by: Scott Prager <splinterofchaos@gmail.com>
Helped-by: oni-link <knil.ino@gmail.com>