Fix a bug in GetOverlappingInputsRangeBinarySearch

[riversand963]

As title.
We pass an argument next_smallest of type InternalKey** to GetOverlappingInputsRangeBinarySearch. In one place inside the function, we perform the following

if (next_smallest) {
  next_smallest = nullptr;
}

This does not have any effect after the function returns. Instead we should do *next_smallest = nullptr.

Test Plan:

$make clean && COMPILE_WITH_ASAN=1 make -j32 all && sleep 1 && make check

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[facebook-github-bot]

@riversand963 merged this pull request in 392f6d4.

[siying]

Can you explain the impact of the bug in the title, and when it was introduced? If it is something already released, also mention it in HISTORY.md.

[riversand963]

@siying @ajkr This is the fix mentioned in #5215
Now I kind of suspect I fixed some dead code...I may be totally wrong, so please let me know.
If you look at CompactionPicker::CompactRange. It calls VersionStorageInfo::GetOverlappingInputs(begin, end) first. If there is no overlapping file, it should return immediately. Only when there is an overlap will execution continue. Later it calls ExpandInputsToCleanCut which calls GetOverlappingInputs with key range that at least include [begin, end]. It seems certain that we will find file(s) overlapping. Therefore the line I changed will never be reached.

[siying]

I know it's the fix mentioned in #5215 but still HISTORY.md should provide a better description.

If it is a dead code, it shouldn't be there and add an assert.

[riversand963]

@siying I should not have used the term 'dead code'. If you pass different arguments to GetOverlappingInputs it is possible to hit this line. Therefore, I don't think we can put an assert.
I have not been able to create a case to show this bug either.

[siying]

@riversand963 just update HISTORY.md to be specific about what the bug is, how it can be triggered and what's the impact.