Change QString formatting of negative numbers in non-base-10

For bases other than 10, negative numbers have been converted
to QString by casting them to an unsigned number and
converting that. Thus QString::number(-17, 16) returned
"0xffffffffffffffef", for example.
This patch changes the behavior so that
negative numbers are converted like positive numbers.
Additinally, this patch adds unit tests for QString::number.

[ChangeLog][Important Behavior Changes]
Changed QString::number(integer, base) for negative numbers
and bases other than 10 to return the string corresponding
to the absolute value, prefixed by "-".

Fixes: QTBUG-53706
Change-Id: I0ad3ca3f035d553860b262f5bec17dc81714d8ac
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 64 insertions, 0 deletions

diff --git a/tests/auto/corelib/text/qstring/tst_qstring.cpp b/tests/auto/corelib/text/qstring/tst_qstring.cpp
index 99f42e2815..47470abd6f 100644
--- a/tests/auto/corelib/text/qstring/tst_qstring.cpp
+++ b/tests/auto/corelib/text/qstring/tst_qstring.cpp
@@ -519,6 +519,8 @@ private slots:
     void toUcs4();
     void arg();
     void number();
+    void number_base_data();
+    void number_base();
     void doubleOut();
     void arg_fillChar_data();
     void arg_fillChar();
@@ -4793,6 +4795,68 @@ void tst_QString::number()
 #endif
 }
 
+void tst_QString::number_base_data()
+{
+    QTest::addColumn<qlonglong>("n");
+    QTest::addColumn<int>("base");
+    QTest::addColumn<QString>("expected");
+
+    QTest::newRow("base 10, positive") << 12346LL << 10 << QString("12346");
+    QTest::newRow("base  2, positive") << 12346LL <<  2 << QString("11000000111010");
+    QTest::newRow("base  8, positive") << 12346LL <<  8 << QString("30072");
+    QTest::newRow("base 16, positive") << 12346LL << 16 << QString("303a");
+    QTest::newRow("base 17, positive") << 12346LL << 17 << QString("28c4");
+    QTest::newRow("base 36, positive") << 2181789482LL << 36 << QString("102zbje");
+
+    QTest::newRow("base 10, negative") << -12346LL << 10 << QString("-12346");
+    QTest::newRow("base  2, negative") << -12346LL <<  2 << QString("-11000000111010");
+    QTest::newRow("base  8, negative") << -12346LL <<  8 << QString("-30072");
+    QTest::newRow("base 16, negative") << -12346LL << 16 << QString("-303a");
+    QTest::newRow("base 17, negative") << -12346LL << 17 << QString("-28c4");
+    QTest::newRow("base 36, negative") << -2181789482LL << 36 << QString("-102zbje");
+
+    QTest::newRow("base  2, negative") << -1LL << 2 << QString("-1");
+
+    QTest::newRow("largeint, base 10, positive")
+            << 123456789012LL << 10 << QString("123456789012");
+    QTest::newRow("largeint, base  2, positive")
+            << 123456789012LL <<  2 << QString("1110010111110100110010001101000010100");
+    QTest::newRow("largeint, base  8, positive")
+            << 123456789012LL <<  8 << QString("1627646215024");
+    QTest::newRow("largeint, base 16, positive")
+            << 123456789012LL << 16 << QString("1cbe991a14");
+    QTest::newRow("largeint, base 17, positive")
+            << 123456789012LL << 17 << QString("10bec2b629");
+
+    QTest::newRow("largeint, base 10, negative")
+            << -123456789012LL << 10 << QString("-123456789012");
+    QTest::newRow("largeint, base  2, negative")
+            << -123456789012LL <<  2 << QString("-1110010111110100110010001101000010100");
+    QTest::newRow("largeint, base  8, negative")
+            << -123456789012LL <<  8 << QString("-1627646215024");
+    QTest::newRow("largeint, base 16, negative")
+            << -123456789012LL << 16 << QString("-1cbe991a14");
+    QTest::newRow("largeint, base 17, negative")
+            << -123456789012LL << 17 << QString("-10bec2b629");
+}
+
+void tst_QString::number_base()
+{
+    QFETCH( qlonglong, n );
+    QFETCH( int, base );
+    QFETCH( QString, expected );
+    QCOMPARE(QString::number(n, base), expected);
+
+    // check qlonglong->QString->qlonglong round trip
+    for (int ibase = 2; ibase <= 36; ++ibase) {
+        auto stringrep = QString::number(n, ibase);
+        bool ok(false);
+        auto result = stringrep.toLongLong(&ok, ibase);
+        QVERIFY(ok);
+        QCOMPARE(n, result);
+    }
+}
+
 void tst_QString::doubleOut()
 {
     // Regression test for QTBUG-63620; the first two paths lost the exponent's