Use C++ <cmath> instead of <math.h>

Including math.h can pollute the default namespace, and break
some compilers if cmath versions of the method are declared as using.

Switching to C++ math functions also greatly simplifies handling of
float qreal as C++ automatically chooses the right method.

[ChangeLog][QtCore][QtMath] qmath.h no longer includes math.h, so any
sources depending on that indirect inclusion may fail to build.

Change-Id: I4d0e331dafba354ec05dc5052e61ef4ff8d387fe
Reviewed-by: Rafael Roquetto <rafael.roquetto@kdab.com>

3 files changed, 9 insertions, 8 deletions

diff --git a/examples/widgets/itemviews/chart/pieview.cpp b/examples/widgets/itemviews/chart/pieview.cpp
index 6e55afa5f0..9793e7d89b 100644
--- a/examples/widgets/itemviews/chart/pieview.cpp
+++ b/examples/widgets/itemviews/chart/pieview.cpp
@@ -38,8 +38,8 @@
 **
 ****************************************************************************/
 
-#include <math.h>
 #include <QtWidgets>
+#include <cmath>
 
 #ifndef M_PI
 #define M_PI 3.1415927
@@ -109,13 +109,13 @@ QModelIndex PieView::indexAt(const QPoint &point) const
         double cy = totalSize / 2 - wy; // positive cy for items above the center
 
         // Determine the distance from the center point of the pie chart.
-        double d = pow(pow(cx, 2) + pow(cy, 2), 0.5);
+        double d = std::sqrt(std::pow(cx, 2) + std::pow(cy, 2));
 
         if (d == 0 || d > pieSize / 2)
             return QModelIndex();
 
         // Determine the angle of the point.
-        double angle = (180 / M_PI) * acos(cx / d);
+        double angle = (180 / M_PI) * std::acos(cx / d);
         if (cy < 0)
             angle = 360 - angle;
 
diff --git a/examples/widgets/itemviews/stardelegate/starrating.cpp b/examples/widgets/itemviews/stardelegate/starrating.cpp
index af67ae11da..568666f93a 100644
--- a/examples/widgets/itemviews/stardelegate/starrating.cpp
+++ b/examples/widgets/itemviews/stardelegate/starrating.cpp
@@ -39,7 +39,7 @@
 ****************************************************************************/
 
 #include <QtWidgets>
-#include <math.h>
+#include <cmath>
 
 #include "starrating.h"
 
@@ -53,8 +53,8 @@ StarRating::StarRating(int starCount, int maxStarCount)
 
     starPolygon << QPointF(1.0, 0.5);
     for (int i = 1; i < 5; ++i)
-        starPolygon << QPointF(0.5 + 0.5 * cos(0.8 * i * 3.14),
-                               0.5 + 0.5 * sin(0.8 * i * 3.14));
+        starPolygon << QPointF(0.5 + 0.5 * std::cos(0.8 * i * 3.14),
+                               0.5 + 0.5 * std::sin(0.8 * i * 3.14));
 
     diamondPolygon << QPointF(0.4, 0.5) << QPointF(0.5, 0.4)
                    << QPointF(0.6, 0.5) << QPointF(0.5, 0.6)
diff --git a/examples/widgets/itemviews/storageview/storagemodel.cpp b/examples/widgets/itemviews/storageview/storagemodel.cpp
index d70f53ce89..9f8d229c77 100644
--- a/examples/widgets/itemviews/storageview/storagemodel.cpp
+++ b/examples/widgets/itemviews/storageview/storagemodel.cpp
@@ -43,6 +43,7 @@
 
 #include <QDir>
 #include <qmath.h>
+#include <cmath>
 
 static QString sizeToString(qint64 size)
 {
@@ -51,11 +52,11 @@ static QString sizeToString(qint64 size)
     if (size <= 0)
         return StorageModel::tr("0 b");
 
-    double power = log((double)size)/log(1024.0);
+    double power = std::log((double)size)/std::log(1024.0);
     int intPower = (int)power;
     intPower = intPower >= 8 ? 8 - 1 : intPower;
 
-    double normSize = size / pow(1024.0, intPower);
+    double normSize = size / std::pow(1024.0, intPower);
     //: this should expand to "1.23 GB"
     return StorageModel::tr("%1 %2").arg(normSize, 0, 'f', intPower > 0 ? 2 : 0).arg(strings[intPower]);
 }