1 files changed, 186 insertions, 0 deletions
diff --git a/tests/auto/corelib/tools/qhashseed/tst_qhashseed.cpp b/tests/auto/corelib/tools/qhashseed/tst_qhashseed.cpp
new file mode 100644
index 0000000000..99fc7c5772
--- /dev/null
+++ b/tests/auto/corelib/tools/qhashseed/tst_qhashseed.cpp
@@ -0,0 +1,186 @@
+// Copyright (C) 2021 Intel Corporation.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
+
+#include <QTest>
+
+#include <qhashfunctions.h>
+#if QT_CONFIG(process)
+#include <qprocess.h>
+#endif
+
+class tst_QHashSeed : public QObject
+{
+    Q_OBJECT
+public:
+    static void initMain();
+
+private Q_SLOTS:
+    void initTestCase();
+    void environmentVariable_data();
+    void environmentVariable();
+    void deterministicSeed();
+    void reseeding();
+    void quality();
+#if QT_VERSION < QT_VERSION_CHECK(7, 0, 0)
+    void compatibilityApi();
+    void deterministicSeed_compat();
+#endif
+};
+
+void tst_QHashSeed::initMain()
+{
+    qunsetenv("QT_HASH_SEED");
+}
+
+void tst_QHashSeed::initTestCase()
+{
+    // in case the qunsetenv above didn't work
+    if (qEnvironmentVariableIsSet("QT_HASH_SEED"))
+        QSKIP("QT_HASH_SEED environment variable is set, please don't do that");
+}
+
+void tst_QHashSeed::environmentVariable_data()
+{
+#ifdef Q_OS_ANDROID
+    QSKIP("This test needs a helper binary, so is excluded from this platform.");
+#endif
+
+    QTest::addColumn<QByteArray>("envVar");
+    QTest::addColumn<bool>("isZero");
+    QTest::newRow("unset-environment") << QByteArray() << false;
+    QTest::newRow("empty-environment") << QByteArray("") << false;
+    QTest::newRow("zero-seed") << QByteArray("0") << true;
+}
+
+void tst_QHashSeed::environmentVariable()
+{
+ #if QT_CONFIG(process)
+    QFETCH(QByteArray, envVar);
+    QFETCH(bool, isZero);
+    QProcessEnvironment env = QProcessEnvironment::systemEnvironment();
+    if (envVar.isNull())
+        env.remove("QT_HASH_SEED");
+    else
+        env.insert("QT_HASH_SEED", envVar);
+
+    QProcess helper;
+    helper.setProcessEnvironment(env);
+    helper.setProgram("./tst_qhashseed_helper");
+    helper.start();
+    QVERIFY2(helper.waitForStarted(5000), qPrintable(helper.errorString()));
+    QVERIFY2(helper.waitForFinished(5000), qPrintable(helper.errorString()));
+    QCOMPARE(helper.exitStatus(), 0);
+
+    QByteArray line1 = helper.readLine().trimmed();
+    QByteArray line2 = helper.readLine().trimmed();
+    QCOMPARE(line2, line1);
+    QCOMPARE(line1 == "0", isZero);
+#endif
+}
+
+void tst_QHashSeed::deterministicSeed()
+{
+    QHashSeed::setDeterministicGlobalSeed();
+    QCOMPARE(size_t(QHashSeed::globalSeed()), size_t(0));
+
+    // now reset
+    QHashSeed::resetRandomGlobalSeed();
+    QVERIFY(QHashSeed::globalSeed() != 0);
+}
+
+void tst_QHashSeed::reseeding()
+{
+    constexpr int Iterations = 4;
+    size_t seeds[Iterations];
+    for (int i = 0; i < Iterations; ++i) {
+        seeds[i] = QHashSeed::globalSeed();
+        QHashSeed::resetRandomGlobalSeed();
+    }
+
+    // verify that they are all different
+    QString fmt = QStringLiteral("seeds[%1] = 0x%3, seeds[%2] = 0x%4");
+    for (int i = 0; i < Iterations; ++i) {
+        for (int j = i + 1; j < Iterations; ++j) {
+            QVERIFY2(seeds[i] != seeds[j],
+                     qPrintable(fmt.arg(i).arg(j).arg(seeds[i], 16).arg(seeds[j], 16)));
+        }
+    }
+}
+
+void tst_QHashSeed::quality()
+{
+    // this "bad seed" is used internally in qhash.cpp and should never leak!
+    constexpr size_t BadSeed = size_t(Q_UINT64_C(0x5555'5555'5555'5555));
+
+    constexpr int Iterations = 24;  // nicely divisible by 3
+    int oneThird = 0;
+    int badSeeds = 0;
+    int seedsToMinus1 = 0;
+    size_t ored = 0;
+
+    for (int i = 0; i < Iterations; ++i) {
+        size_t seed = QHashSeed::globalSeed();
+        ored |= seed;
+        int bits = qPopulationCount(quintptr(seed));
+        QVERIFY2(bits > 0, QByteArray::number(bits));   // mandatory
+
+        if (bits >= std::numeric_limits<size_t>::digits / 3)
+            ++oneThird;
+        if (seed == BadSeed)
+            ++badSeeds;
+        if (ored != size_t(-1))
+            ++seedsToMinus1;
+
+        QHashSeed::resetRandomGlobalSeed();
+    }
+
+    // report out
+    qInfo() << "Number of seeds until all bits became set:" << seedsToMinus1 << '/' << Iterations;
+    qInfo() << "Number of seeds with at least one third of the bits set:"
+            << oneThird << '/' << Iterations;
+
+    // we must have set all bits after all the iterations
+    QCOMPARE(ored, size_t(-1));
+
+    // at least one third of the seeds must have one third of all the bits set
+    QVERIFY(oneThird > (Iterations/3));
+
+    // at most one seed can be the bad seed, if 32-bit, none on 64-bit
+    if (std::numeric_limits<size_t>::digits > 32)
+        QCOMPARE(badSeeds, 0);
+    else
+        QVERIFY2(badSeeds <= 1, "badSeeds = " + QByteArray::number(badSeeds));
+
+    // we must have taken at most two thirds of the iterations to have set each
+    // bit at least once
+    QVERIFY2(seedsToMinus1 < 2*Iterations/3,
+             "seedsToMinus1 = " + QByteArray::number(seedsToMinus1));
+}
+
+#if QT_VERSION < QT_VERSION_CHECK(7, 0, 0)
+QT_WARNING_DISABLE_DEPRECATED
+void tst_QHashSeed::compatibilityApi()
+{
+    int oldSeed = qGlobalQHashSeed();
+    size_t newSeed = QHashSeed::globalSeed();
+
+    QCOMPARE(size_t(oldSeed), newSeed & size_t(INT_MAX));
+}
+
+void tst_QHashSeed::deterministicSeed_compat()
+{
+    // same as above, but using the compat API
+    qSetGlobalQHashSeed(0);
+    QCOMPARE(size_t(QHashSeed::globalSeed()), size_t(0));
+    QCOMPARE(qGlobalQHashSeed(), 0);
+
+    // now reset
+    qSetGlobalQHashSeed(-1);
+    QVERIFY(QHashSeed::globalSeed() != 0);
+    QVERIFY(qGlobalQHashSeed() != 0);
+    QVERIFY(qGlobalQHashSeed() != -1);  // possible, but extremely unlikely
+}
+#endif // Qt 7
+
+QTEST_MAIN(tst_QHashSeed)
+#include "tst_qhashseed.moc"