Summary

The GranularityRounder helpers (granularity_rounder_powers_of_two.cpp and granularity_rounder_preferred_numbers.cpp) do not reject non-finite (infinity) numeric input. When a user pipeline feeds Infinity into $bucketAuto with a granularity (e.g. POWERSOF2), execution reaches representAsChecked<int>(...) with a non-finite double, which trips a tassert (BF-44396).

Reproducer

db.fuzzer_coll.aggregate([
  {$sort: {_id: 1}},
  {$bucketAuto: {
     groupBy: {$trunc: {$numberDouble: "Infinity"}},
     buckets: 12,
     output: {num: {$max: {$bitOr: [1611, 46718, 89496]}}},
     granularity: "POWERSOF2"
  }}
])

Stack

representAsChecked<int,double>                       represent_as_util.h:43
GranularityRounderPowersOfTwo::roundDown             granularity_rounder_powers_of_two.cpp:99
DocumentSourceBucketAuto::populateNextBucket         document_source_bucket_auto.cpp:320
DocumentSourceBucketAuto::doGetNext                  document_source_bucket_auto.cpp:111

Tripwire: code 12961701 ("cannot represent value as target type").

Root cause

uassertNonNegativeNumber() in both granularity rounder files rejects non-numeric, NaN, and negative values, but not Infinity. Downstream, std::log2(Inf) = Inf, std::ceil(Inf) - 1 = Inf, and then representAsChecked<int>(Inf) fails. (Note: a plain static_cast<int>(Inf) is undefined behavior in C+ — the whole point of representAsChecked is to catch this.)

Fix

Extend uassertNonNegativeNumber in both files to also assert std::isfinite(number), converting this into a user-facing uassert with a clear message ("A granularity rounder cannot round infinity").

Affected branches

The missing infinity guard is old code, so v7.0, v8.0, v8.2, v8.3, and master all have the latent hole.

Related

BF-44396