4 files changed, 37 insertions, 2 deletions
diff --git a/src/corelib/json/qjson_p.h b/src/corelib/json/qjson_p.h
index 06885ad972..7d0162938d 100644
--- a/src/corelib/json/qjson_p.h
+++ b/src/corelib/json/qjson_p.h
@@ -60,8 +60,10 @@
 #include <qatomic.h>
 #include <qstring.h>
 #include <qendian.h>
+#include <qnumeric.h>
 
 #include <limits.h>
+#include <limits>
 
 QT_BEGIN_NAMESPACE
 
diff --git a/src/corelib/json/qjsonvalue.cpp b/src/corelib/json/qjsonvalue.cpp
index 9dd9a9cab9..d0634602f3 100644
--- a/src/corelib/json/qjsonvalue.cpp
+++ b/src/corelib/json/qjsonvalue.cpp
@@ -158,6 +158,18 @@ QJsonValue::QJsonValue(int n)
 }
 
 /*!
+    \overload
+    Creates a value of type Double, with value \a n.
+    NOTE: the integer limits for IEEE 754 double precision data is 2^53 (-9007199254740992 to +9007199254740992).
+    If you pass in values outside this range expect a loss of precision to occur.
+ */
+QJsonValue::QJsonValue(qint64 n)
+    : d(0), t(Double)
+{
+    this->dbl = n;
+}
+
+/*!
     Creates a value of type String, with value \a s.
  */
 QJsonValue::QJsonValue(const QString &s)
@@ -439,6 +451,19 @@ bool QJsonValue::toBool(bool defaultValue) const
 }
 
 /*!
+    Converts the value to an int and returns it.
+
+    If type() is not Double or the value is not a whole number,
+    the \a defaultValue will be returned.
+ */
+int QJsonValue::toInt(int defaultValue) const
+{
+    if (t == Double && int(dbl) == dbl)
+        return dbl;
+    return defaultValue;
+}
+
+/*!
     Converts the value to a double and returns it.
 
     If type() is not Double, the \a defaultValue will be returned.
diff --git a/src/corelib/json/qjsonvalue.h b/src/corelib/json/qjsonvalue.h
index b8bdf55aa3..b18bbde0f7 100644
--- a/src/corelib/json/qjsonvalue.h
+++ b/src/corelib/json/qjsonvalue.h
@@ -79,6 +79,7 @@ public:
     QJsonValue(bool b);
     QJsonValue(double n);
     QJsonValue(int n);
+    QJsonValue(qint64 n);
     QJsonValue(const QString &s);
     QJsonValue(QLatin1String s);
     QJsonValue(const QJsonArray &a);
@@ -102,6 +103,7 @@ public:
     inline bool isUndefined() const { return type() == Undefined; }
 
     bool toBool(bool defaultValue = false) const;
+    int toInt(int defaultValue = 0) const;
     double toDouble(double defaultValue = 0) const;
     QString toString(const QString &defaultValue = QString()) const;
     QJsonArray toArray() const;
@@ -157,6 +159,7 @@ public:
     inline bool isUndefined() const { return type() == QJsonValue::Undefined; }
 
     inline bool toBool() const { return toValue().toBool(); }
+    inline int toInt() const { return toValue().toInt(); }
     inline double toDouble() const { return toValue().toDouble(); }
     inline QString toString() const { return toValue().toString(); }
     QJsonArray toArray() const;
diff --git a/src/corelib/json/qjsonwriter.cpp b/src/corelib/json/qjsonwriter.cpp
index 3ac16c6fd1..8426b351f6 100644
--- a/src/corelib/json/qjsonwriter.cpp
+++ b/src/corelib/json/qjsonwriter.cpp
@@ -169,9 +169,14 @@ static void valueToJson(const QJsonPrivate::Base *b, const QJsonPrivate::Value &
     case QJsonValue::Bool:
         json += v.toBoolean() ? "true" : "false";
         break;
-    case QJsonValue::Double:
-        json += QByteArray::number(v.toDouble(b), 'g', 17);
+    case QJsonValue::Double: {
+        const double d = v.toDouble(b);
+        if (qIsFinite(d)) // +2 to format to ensure the expected precision
+            json += QByteArray::number(d, 'g', std::numeric_limits<double>::digits10 + 2); // ::digits10 is 15
+        else
+            json += "null"; // +INF || -INF || NaN (see RFC4627#section2.4)
         break;
+    }
     case QJsonValue::String:
         json += '"';
         json += escapedString(v.toString(b));