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path: root/jstests/core/mod_overflow.js
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/**
 * Tests that modding the smallest representable integer values by -1 does not result in integer
 * overflow. Exercises the fix for SERVER-43699.
 */
(function() {
    "use strict";

    const testDB = db.getSiblingDB(jsTestName());
    const testColl = testDB.test;
    testColl.drop();

    // Insert two documents, one with a value of -2^63 and the other with a value of -2^31.
    const insertedDocs = [
        {_id: 0, val: NumberLong("-9223372036854775808")},
        {_id: 1, val: NumberInt("-2147483648")}
    ];
    assert.writeOK(testColl.insert(insertedDocs));

    // For each possible integral representation of -1, confirm that overflow does not occur.
    for (let divisor of[-1.0, NumberInt("-1"), NumberLong("-1"), NumberDecimal("-1")]) {
        assert.docEq(testColl.find({val: {$mod: [divisor, 0]}}).sort({_id: 1}).toArray(),
                     insertedDocs);
        assert.docEq(
            testColl
                .aggregate(
                    [{$match: {$expr: {$eq: [0, {$mod: ["$val", divisor]}]}}}, {$sort: {_id: 1}}])
                .toArray(),
            insertedDocs);

        // Confirm that overflow does not occur during agg expression evaluation. Also confirm that
        // the correct type is returned for each combination of input types.
        const expectedResults = [
            Object.merge(insertedDocs[0], {
                modVal: (divisor instanceof NumberDecimal ? NumberDecimal("-0") : NumberLong("0"))
            }),
            Object.merge(insertedDocs[1], {
                modVal: (divisor instanceof NumberLong
                             ? NumberLong("0")
                             : divisor instanceof NumberDecimal ? NumberDecimal("-0") : 0)
            })
        ];
        assert.docEq(
            testColl
                .aggregate(
                    [{$project: {val: 1, modVal: {$mod: ["$val", divisor]}}}, {$sort: {_id: 1}}])
                .toArray(),
            expectedResults);
    }
})();