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>

24 files changed, 123 insertions, 189 deletions

diff --git a/src/corelib/doc/snippets/code/doc_src_qiterator.cpp b/src/corelib/doc/snippets/code/doc_src_qiterator.cpp
index e37212b475..c311db957c 100644
--- a/src/corelib/doc/snippets/code/doc_src_qiterator.cpp
+++ b/src/corelib/doc/snippets/code/doc_src_qiterator.cpp
@@ -257,7 +257,7 @@ while (i.hasNext()) {
 QMutableListIterator<double> i(list);
 while (i.hasNext()) {
     double val = i.next();
-    i.setValue(sqrt(val));
+    i.setValue(std::sqrt(val));
 }
 //! [23]
 
@@ -266,7 +266,7 @@ while (i.hasNext()) {
 QMutableLinkedListIterator<double> i(list);
 while (i.hasNext()) {
     double val = i.next();
-    i.setValue(sqrt(val));
+    i.setValue(std::sqrt(val));
 }
 //! [24]
 
@@ -275,7 +275,7 @@ while (i.hasNext()) {
 QMutableVectorIterator<double> i(list);
 while (i.hasNext()) {
     double val = i.next();
-    i.setValue(sqrt(val));
+    i.setValue(std::sqrt(val));
 }
 //! [25]
 
diff --git a/src/corelib/doc/snippets/code/src_corelib_tools_qpoint.cpp b/src/corelib/doc/snippets/code/src_corelib_tools_qpoint.cpp
index 17a252cc1b..b545c2dad8 100644
--- a/src/corelib/doc/snippets/code/src_corelib_tools_qpoint.cpp
+++ b/src/corelib/doc/snippets/code/src_corelib_tools_qpoint.cpp
@@ -105,7 +105,7 @@ MyWidget::mouseMoveEvent(QMouseEvent *event)
 
 
 //! [8]
-double trueLength = sqrt(pow(x(), 2) + pow(y(), 2));
+double trueLength = std::sqrt(std::pow(x(), 2) + std::pow(y(), 2));
 //! [8]
 
 
diff --git a/src/corelib/kernel/qmath.h b/src/corelib/kernel/qmath.h
index 2395e9ee1c..5cc3ec586e 100644
--- a/src/corelib/kernel/qmath.h
+++ b/src/corelib/kernel/qmath.h
@@ -38,13 +38,11 @@
 #pragma qt_class(QtMath)
 #endif
 
-#include <math.h>
-
 #include <QtCore/qglobal.h>
-#include <QtCore/qcompilerdetection.h>
 
-QT_BEGIN_NAMESPACE
+#include <cmath>
 
+QT_BEGIN_NAMESPACE
 
 #define QT_SINE_TABLE_SIZE 256
 
@@ -52,139 +50,86 @@ extern Q_CORE_EXPORT const qreal qt_sine_table[QT_SINE_TABLE_SIZE];
 
 inline int qCeil(qreal v)
 {
-#ifdef QT_USE_MATH_H_FLOATS
-    if (sizeof(qreal) == sizeof(float))
-        return int(ceilf(float(v)));
-    else
-#endif
-        return int(ceil(v));
+    using std::ceil;
+    return int(ceil(v));
 }
 
 inline int qFloor(qreal v)
 {
-#ifdef QT_USE_MATH_H_FLOATS
-    if (sizeof(qreal) == sizeof(float))
-        return int(floorf(float(v)));
-    else
-#endif
-        return int(floor(v));
+    using std::floor;
+    return int(floor(v));
 }
 
 inline qreal qFabs(qreal v)
 {
-#ifdef QT_USE_MATH_H_FLOATS
-    if(sizeof(qreal) == sizeof(float))
-        return fabsf(float(v));
-    else
-#endif
-        return fabs(v);
+    using std::fabs;
+    return fabs(v);
 }
 
 inline qreal qSin(qreal v)
 {
-#ifdef QT_USE_MATH_H_FLOATS
-    if (sizeof(qreal) == sizeof(float))
-        return sinf(float(v));
-    else
-#endif
-        return sin(v);
+    using std::sin;
+    return sin(v);
 }
 
 inline qreal qCos(qreal v)
 {
-#ifdef QT_USE_MATH_H_FLOATS
-    if (sizeof(qreal) == sizeof(float))
-        return cosf(float(v));
-    else
-#endif
-        return cos(v);
+    using std::cos;
+    return cos(v);
 }
 
 inline qreal qTan(qreal v)
 {
-#ifdef QT_USE_MATH_H_FLOATS
-    if (sizeof(qreal) == sizeof(float))
-        return tanf(float(v));
-    else
-#endif
-        return tan(v);
+    using std::tan;
+    return tan(v);
 }
 
 inline qreal qAcos(qreal v)
 {
-#ifdef QT_USE_MATH_H_FLOATS
-    if (sizeof(qreal) == sizeof(float))
-        return acosf(float(v));
-    else
-#endif
-       return acos(v);
+    using std::acos;
+    return acos(v);
 }
 
 inline qreal qAsin(qreal v)
 {
-#ifdef QT_USE_MATH_H_FLOATS
-    if (sizeof(qreal) == sizeof(float))
-        return asinf(float(v));
-    else
-#endif
-        return asin(v);
+    using std::asin;
+    return asin(v);
 }
 
 inline qreal qAtan(qreal v)
 {
-#ifdef QT_USE_MATH_H_FLOATS
-    if (sizeof(qreal) == sizeof(float))
-        return atanf(float(v));
-    else
-#endif
-        return atan(v);
+    using std::atan;
+    return atan(v);
 }
 
 inline qreal qAtan2(qreal y, qreal x)
 {
-#ifdef QT_USE_MATH_H_FLOATS
-    if (sizeof(qreal) == sizeof(float))
-        return atan2f(float(y), float(x));
-    else
-#endif
-        return atan2(y, x);
+    using std::atan2;
+    return atan2(y, x);
 }
 
 inline qreal qSqrt(qreal v)
 {
-#ifdef QT_USE_MATH_H_FLOATS
-    if (sizeof(qreal) == sizeof(float))
-        return sqrtf(float(v));
-    else
-#endif
-        return sqrt(v);
+    using std::sqrt;
+    return sqrt(v);
 }
 
 inline qreal qLn(qreal v)
 {
-#ifdef QT_USE_MATH_H_FLOATS
-    if (sizeof(qreal) == sizeof(float))
-        return logf(float(v));
-    else
-#endif
-        return log(v);
+    using std::log;
+    return log(v);
 }
 
 inline qreal qExp(qreal v)
 {
-    // only one signature
-    // exists, exp(double)
+    using std::exp;
     return exp(v);
 }
 
 inline qreal qPow(qreal x, qreal y)
 {
-#ifdef QT_USE_MATH_H_FLOATS
-    if (sizeof(qreal) == sizeof(float))
-        return powf(float(x), float(y));
-    else
-#endif
-        return pow(x, y);
+    using std::pow;
+    return pow(x, y);
 }
 
 #ifndef M_E
diff --git a/src/corelib/tools/qeasingcurve.cpp b/src/corelib/tools/qeasingcurve.cpp
index c1d74b3b43..1bd9c5ebb9 100644
--- a/src/corelib/tools/qeasingcurve.cpp
+++ b/src/corelib/tools/qeasingcurve.cpp
@@ -657,7 +657,7 @@ struct BezierEase : public QEasingCurveFunction
 
     qreal static inline _acos(qreal x)
     {
-        return sqrt(1-x)*(1.5707963267948966192313216916398f + x*(-0.213300989f + x*(0.077980478f + x*-0.02164095f)));
+        return std::sqrt(1-x)*(1.5707963267948966192313216916398f + x*(-0.213300989f + x*(0.077980478f + x*-0.02164095f)));
     }
 
     qreal static inline _cos(qreal x) //super fast _cos
@@ -704,8 +704,8 @@ struct BezierEase : public QEasingCurveFunction
         //We use approximations instead
 
         const qreal x_squared = x * x;
-        const qreal x_plus_one_sqrt = sqrt(1.0 + x);
-        const qreal one_minus_x_sqrt = sqrt(1.0 - x);
+        const qreal x_plus_one_sqrt = qSqrt(1.0 + x);
+        const qreal one_minus_x_sqrt = qSqrt(1.0 - x);
 
         //cos(acos(x) / 3)
         //s1 = _cos(_acos(x) / 3);
@@ -743,7 +743,7 @@ struct BezierEase : public QEasingCurveFunction
         const qreal D = 0.25 * q_squared + p_cubic / 27.0;
 
         if (D >= 0) {
-            const qreal D_sqrt = sqrt(D);
+            const qreal D_sqrt = qSqrt(D);
             qreal u = _cbrt( -q * 0.5 + D_sqrt);
             qreal v = _cbrt( -q * 0.5 - D_sqrt);
             qreal z1 = u + v;
@@ -758,13 +758,13 @@ struct BezierEase : public QEasingCurveFunction
         }
 
         //casus irreducibilis
-        const qreal p_minus_sqrt = sqrt(-p);
+        const qreal p_minus_sqrt = qSqrt(-p);
 
         //const qreal f = sqrt(4.0 / 3.0 * -p);
-        const qreal f = sqrt(4.0 / 3.0) * p_minus_sqrt;
+        const qreal f = qSqrt(4.0 / 3.0) * p_minus_sqrt;
 
         //const qreal sqrtP = sqrt(27.0 / -p_cubic);
-        const qreal sqrtP = -3.0*sqrt(3.0) / (p_minus_sqrt * p);
+        const qreal sqrtP = -3.0*qSqrt(3.0) / (p_minus_sqrt * p);
 
 
         const qreal g = -q * 0.5 * sqrtP;
diff --git a/src/gui/math3d/qmatrix4x4.cpp b/src/gui/math3d/qmatrix4x4.cpp
index 42aae6c20c..c196f7cff8 100644
--- a/src/gui/math3d/qmatrix4x4.cpp
+++ b/src/gui/math3d/qmatrix4x4.cpp
@@ -1125,8 +1125,8 @@ void QMatrix4x4::rotate(float angle, float x, float y, float z)
         c = -1.0f;
     } else {
         float a = angle * M_PI / 180.0f;
-        c = cosf(a);
-        s = sinf(a);
+        c = std::cos(a);
+        s = std::sin(a);
     }
     if (x == 0.0f) {
         if (y == 0.0f) {
@@ -1186,7 +1186,7 @@ void QMatrix4x4::rotate(float angle, float x, float y, float z)
                  double(y) * double(y) +
                  double(z) * double(z);
     if (!qFuzzyCompare(len, 1.0) && !qFuzzyIsNull(len)) {
-        len = sqrt(len);
+        len = std::sqrt(len);
         x = float(double(x) / len);
         y = float(double(y) / len);
         z = float(double(z) / len);
@@ -1234,8 +1234,8 @@ void QMatrix4x4::projectedRotate(float angle, float x, float y, float z)
         c = -1.0f;
     } else {
         float a = angle * M_PI / 180.0f;
-        c = cosf(a);
-        s = sinf(a);
+        c = std::cos(a);
+        s = std::sin(a);
     }
     if (x == 0.0f) {
         if (y == 0.0f) {
@@ -1282,7 +1282,7 @@ void QMatrix4x4::projectedRotate(float angle, float x, float y, float z)
                  double(y) * double(y) +
                  double(z) * double(z);
     if (!qFuzzyCompare(len, 1.0) && !qFuzzyIsNull(len)) {
-        len = sqrt(len);
+        len = std::sqrt(len);
         x = float(double(x) / len);
         y = float(double(y) / len);
         z = float(double(z) / len);
@@ -1487,10 +1487,10 @@ void QMatrix4x4::perspective(float verticalAngle, float aspectRatio, float nearP
     // Construct the projection.
     QMatrix4x4 m(1);
     float radians = (verticalAngle / 2.0f) * M_PI / 180.0f;
-    float sine = sinf(radians);
+    float sine = std::sin(radians);
     if (sine == 0.0f)
         return;
-    float cotan = cosf(radians) / sine;
+    float cotan = std::cos(radians) / sine;
     float clip = farPlane - nearPlane;
     m.m[0][0] = cotan / aspectRatio;
     m.m[1][0] = 0.0f;
diff --git a/src/gui/math3d/qquaternion.cpp b/src/gui/math3d/qquaternion.cpp
index 0653ace5a4..f2e79cb834 100644
--- a/src/gui/math3d/qquaternion.cpp
+++ b/src/gui/math3d/qquaternion.cpp
@@ -219,7 +219,7 @@ QT_BEGIN_NAMESPACE
 */
 float QQuaternion::length() const
 {
-    return qSqrt(xp * xp + yp * yp + zp * zp + wp * wp);
+    return std::sqrt(xp * xp + yp * yp + zp * zp + wp * wp);
 }
 
 /*!
@@ -252,7 +252,7 @@ QQuaternion QQuaternion::normalized() const
     if (qFuzzyIsNull(len - 1.0f))
         return *this;
     else if (!qFuzzyIsNull(len))
-        return *this / qSqrt(len);
+        return *this / std::sqrt(len);
     else
         return QQuaternion(0.0f, 0.0f, 0.0f, 0.0f);
 }
@@ -273,7 +273,7 @@ void QQuaternion::normalize()
     if (qFuzzyIsNull(len - 1.0f) || qFuzzyIsNull(len))
         return;
 
-    len = qSqrt(len);
+    len = std::sqrt(len);
 
     xp /= len;
     yp /= len;
@@ -386,8 +386,8 @@ QQuaternion QQuaternion::fromAxisAndAngle(const QVector3D& axis, float angle)
     // We normalize the result just in case the values are close
     // to zero, as suggested in the above FAQ.
     float a = (angle / 2.0f) * M_PI / 180.0f;
-    float s = sinf(a);
-    float c = cosf(a);
+    float s = std::sin(a);
+    float c = std::cos(a);
     QVector3D ax = axis.normalized();
     return QQuaternion(c, ax.x() * s, ax.y() * s, ax.z() * s).normalized();
 }
@@ -415,12 +415,12 @@ void QQuaternion::toAxisAndAngle(float *x, float *y, float *z, float *angle) con
         *y = yp;
         *z = zp;
         if (!qFuzzyIsNull(length - 1.0f)) {
-            length = sqrtf(length);
+            length = std::sqrt(length);
             *x /= length;
             *y /= length;
             *z /= length;
         }
-        *angle = 2.0f * acosf(wp);
+        *angle = 2.0f * std::acos(wp);
     } else {
         // angle is 0 (mod 2*pi), so any axis will fit
         *x = *y = *z = *angle = 0.0f;
@@ -438,15 +438,15 @@ void QQuaternion::toAxisAndAngle(float *x, float *y, float *z, float *angle) con
 QQuaternion QQuaternion::fromAxisAndAngle
         (float x, float y, float z, float angle)
 {
-    float length = qSqrt(x * x + y * y + z * z);
+    float length = std::sqrt(x * x + y * y + z * z);
     if (!qFuzzyIsNull(length - 1.0f) && !qFuzzyIsNull(length)) {
         x /= length;
         y /= length;
         z /= length;
     }
     float a = (angle / 2.0f) * M_PI / 180.0f;
-    float s = sinf(a);
-    float c = cosf(a);
+    float s = std::sin(a);
+    float c = std::cos(a);
     return QQuaternion(c, x * s, y * s, z * s).normalized();
 }
 
@@ -515,20 +515,20 @@ void QQuaternion::toEulerAngles(float *pitch, float *yaw, float *roll) const
         zw /= lengthSquared;
     }
 
-    *pitch = asinf(-2.0f * (yz - xw));
+    *pitch = std::asin(-2.0f * (yz - xw));
     if (*pitch < M_PI_2) {
         if (*pitch > -M_PI_2) {
-            *yaw = atan2f(2.0f * (xz + yw), 1.0f - 2.0f * (xx + yy));
-            *roll = atan2f(2.0f * (xy + zw), 1.0f - 2.0f * (xx + zz));
+            *yaw = std::atan2(2.0f * (xz + yw), 1.0f - 2.0f * (xx + yy));
+            *roll = std::atan2(2.0f * (xy + zw), 1.0f - 2.0f * (xx + zz));
         } else {
             // not a unique solution
             *roll = 0.0f;
-            *yaw = -atan2f(-2.0f * (xy - zw), 1.0f - 2.0f * (yy + zz));
+            *yaw = -std::atan2(-2.0f * (xy - zw), 1.0f - 2.0f * (yy + zz));
         }
     } else {
         // not a unique solution
         *roll = 0.0f;
-        *yaw = atan2f(-2.0f * (xy - zw), 1.0f - 2.0f * (yy + zz));
+        *yaw = std::atan2(-2.0f * (xy - zw), 1.0f - 2.0f * (yy + zz));
     }
 
     *pitch = qRadiansToDegrees(*pitch);
@@ -558,12 +558,12 @@ QQuaternion QQuaternion::fromEulerAngles(float pitch, float yaw, float roll)
     yaw *= 0.5f;
     roll *= 0.5f;
 
-    const float c1 = cosf(yaw);
-    const float s1 = sinf(yaw);
-    const float c2 = cosf(roll);
-    const float s2 = sinf(roll);
-    const float c3 = cosf(pitch);
-    const float s3 = sinf(pitch);
+    const float c1 = std::cos(yaw);
+    const float s1 = std::sin(yaw);
+    const float c2 = std::cos(roll);
+    const float s2 = std::sin(roll);
+    const float c3 = std::cos(pitch);
+    const float s3 = std::sin(pitch);
     const float c1c2 = c1 * c2;
     const float s1s2 = s1 * s2;
 
@@ -635,7 +635,7 @@ QQuaternion QQuaternion::fromRotationMatrix(const QMatrix3x3 &rot3x3)
 
     const float trace = rot3x3(0, 0) + rot3x3(1, 1) + rot3x3(2, 2);
     if (trace > 0.00000001f) {
-        const float s = 2.0f * sqrtf(trace + 1.0f);
+        const float s = 2.0f * std::sqrt(trace + 1.0f);
         scalar = 0.25f * s;
         axis[0] = (rot3x3(2, 1) - rot3x3(1, 2)) / s;
         axis[1] = (rot3x3(0, 2) - rot3x3(2, 0)) / s;
@@ -650,7 +650,7 @@ QQuaternion QQuaternion::fromRotationMatrix(const QMatrix3x3 &rot3x3)
         int j = s_next[i];
         int k = s_next[j];
 
-        const float s = 2.0f * sqrtf(rot3x3(i, i) - rot3x3(j, j) - rot3x3(k, k) + 1.0f);
+        const float s = 2.0f * std::sqrt(rot3x3(i, i) - rot3x3(j, j) - rot3x3(k, k) + 1.0f);
         axis[i] = 0.25f * s;
         scalar = (rot3x3(k, j) - rot3x3(j, k)) / s;
         axis[j] = (rot3x3(j, i) + rot3x3(i, j)) / s;
@@ -792,11 +792,11 @@ QQuaternion QQuaternion::slerp
     float factor1 = 1.0f - t;
     float factor2 = t;
     if ((1.0f - dot) > 0.0000001) {
-        float angle = acosf(dot);
-        float sinOfAngle = sinf(angle);
+        float angle = std::acos(dot);
+        float sinOfAngle = std::sin(angle);
         if (sinOfAngle > 0.0000001) {
-            factor1 = sinf((1.0f - t) * angle) / sinOfAngle;
-            factor2 = sinf(t * angle) / sinOfAngle;
+            factor1 = std::sin((1.0f - t) * angle) / sinOfAngle;
+            factor2 = std::sin(t * angle) / sinOfAngle;
         }
     }
 
diff --git a/src/gui/math3d/qvector2d.cpp b/src/gui/math3d/qvector2d.cpp
index bad46c6e0b..fe4c9f8cc2 100644
--- a/src/gui/math3d/qvector2d.cpp
+++ b/src/gui/math3d/qvector2d.cpp
@@ -189,7 +189,7 @@ float QVector2D::length() const
     // Need some extra precision if the length is very small.
     double len = double(xp) * double(xp) +
                  double(yp) * double(yp);
-    return float(sqrt(len));
+    return float(std::sqrt(len));
 }
 
 /*!
@@ -220,7 +220,7 @@ QVector2D QVector2D::normalized() const
     if (qFuzzyIsNull(len - 1.0f)) {
         return *this;
     } else if (!qFuzzyIsNull(len)) {
-        double sqrtLen = sqrt(len);
+        double sqrtLen = std::sqrt(len);
         return QVector2D(float(double(xp) / sqrtLen), float(double(yp) / sqrtLen));
     } else {
         return QVector2D();
@@ -241,7 +241,7 @@ void QVector2D::normalize()
     if (qFuzzyIsNull(len - 1.0f) || qFuzzyIsNull(len))
         return;
 
-    len = sqrt(len);
+    len = std::sqrt(len);
 
     xp = float(double(xp) / len);
     yp = float(double(yp) / len);
diff --git a/src/gui/math3d/qvector3d.cpp b/src/gui/math3d/qvector3d.cpp
index fa09a43480..a93d994a70 100644
--- a/src/gui/math3d/qvector3d.cpp
+++ b/src/gui/math3d/qvector3d.cpp
@@ -235,7 +235,7 @@ QVector3D QVector3D::normalized() const
     if (qFuzzyIsNull(len - 1.0f)) {
         return *this;
     } else if (!qFuzzyIsNull(len)) {
-        double sqrtLen = sqrt(len);
+        double sqrtLen = std::sqrt(len);
         return QVector3D(float(double(xp) / sqrtLen),
                          float(double(yp) / sqrtLen),
                          float(double(zp) / sqrtLen));
@@ -259,7 +259,7 @@ void QVector3D::normalize()
     if (qFuzzyIsNull(len - 1.0f) || qFuzzyIsNull(len))
         return;
 
-    len = sqrt(len);
+    len = std::sqrt(len);
 
     xp = float(double(xp) / len);
     yp = float(double(yp) / len);
@@ -679,7 +679,7 @@ float QVector3D::length() const
     double len = double(xp) * double(xp) +
                  double(yp) * double(yp) +
                  double(zp) * double(zp);
-    return float(sqrt(len));
+    return float(std::sqrt(len));
 }
 
 /*!
diff --git a/src/gui/math3d/qvector4d.cpp b/src/gui/math3d/qvector4d.cpp
index 1eed1c1301..6afe9b8cad 100644
--- a/src/gui/math3d/qvector4d.cpp
+++ b/src/gui/math3d/qvector4d.cpp
@@ -256,7 +256,7 @@ float QVector4D::length() const
                  double(yp) * double(yp) +
                  double(zp) * double(zp) +
                  double(wp) * double(wp);
-    return float(sqrt(len));
+    return float(std::sqrt(len));
 }
 
 /*!
@@ -289,7 +289,7 @@ QVector4D QVector4D::normalized() const
     if (qFuzzyIsNull(len - 1.0f)) {
         return *this;
     } else if (!qFuzzyIsNull(len)) {
-        double sqrtLen = sqrt(len);
+        double sqrtLen = std::sqrt(len);
         return QVector4D(float(double(xp) / sqrtLen),
                          float(double(yp) / sqrtLen),
                          float(double(zp) / sqrtLen),
@@ -315,7 +315,7 @@ void QVector4D::normalize()
     if (qFuzzyIsNull(len - 1.0f) || qFuzzyIsNull(len))
         return;
 
-    len = sqrt(len);
+    len = std::sqrt(len);
 
     xp = float(double(xp) / len);
     yp = float(double(yp) / len);
diff --git a/src/gui/opengl/qopenglpaintengine.cpp b/src/gui/opengl/qopenglpaintengine.cpp
index c23e0c28ea..576558022e 100644
--- a/src/gui/opengl/qopenglpaintengine.cpp
+++ b/src/gui/opengl/qopenglpaintengine.cpp
@@ -462,8 +462,8 @@ void QOpenGL2PaintEngineExPrivate::updateMatrix()
     // anti-aliased text rendering. In such cases, we snap the translate to the pixel grid.
     if (snapToPixelGrid && transform.type() == QTransform::TxTranslate) {
         // 0.50 needs to rounded down to 0.0 for consistency with raster engine:
-        dx = ceilf(dx - 0.5f);
-        dy = ceilf(dy - 0.5f);
+        dx = std::ceil(dx - 0.5f);
+        dy = std::ceil(dy - 0.5f);
     }
     pmvMatrix[0][0] = (wfactor * transform.m11())  - transform.m13();
     pmvMatrix[1][0] = (wfactor * transform.m21())  - transform.m23();
diff --git a/src/gui/opengl/qtriangulatingstroker_p.h b/src/gui/opengl/qtriangulatingstroker_p.h
index 2561810d7a..dd46cbe1e5 100644
--- a/src/gui/opengl/qtriangulatingstroker_p.h
+++ b/src/gui/opengl/qtriangulatingstroker_p.h
@@ -134,11 +134,11 @@ inline void QTriangulatingStroker::normalVector(float x1, float y1, float x2, fl
     float pw;
 
     if (dx == 0)
-        pw = m_width / qAbs(dy);
+        pw = m_width / std::abs(dy);
     else if (dy == 0)
-        pw = m_width / qAbs(dx);
+        pw = m_width / std::abs(dx);
     else
-        pw = m_width / sqrt(dx*dx + dy*dy);
+        pw = m_width / std::sqrt(dx*dx + dy*dy);
 
     *nx = -dy * pw;
     *ny = dx * pw;
diff --git a/src/gui/opengl/qtriangulator.cpp b/src/gui/opengl/qtriangulator.cpp
index b0d754b87e..6574fe9975 100644
--- a/src/gui/opengl/qtriangulator.cpp
+++ b/src/gui/opengl/qtriangulator.cpp
@@ -49,8 +49,6 @@
 #include <private/qopenglextensions_p.h>
 #include <private/qrbtree_p.h>
 
-#include <math.h>
-
 QT_BEGIN_NAMESPACE
 
 //#define Q_TRIANGULATOR_DEBUG
@@ -1700,8 +1698,8 @@ void QTriangulator<T>::ComplexToSimple::DebugDialog::paintEvent(QPaintEvent *)
         QPodPoint q = vertices.at(splits.at(i).vertex);
         QPodPoint u = vertices.at(edges.at(splits.at(i).edge).from) - q;
         QPodPoint v = vertices.at(edges.at(splits.at(i).edge).to) - q;
-        qreal uLen = sqrt(qreal(qDot(u, u)));
-        qreal vLen = sqrt(qreal(qDot(v, v)));
+        qreal uLen = qSqrt(qDot(u, u));
+        qreal vLen = qSqrt(qDot(v, v));
         if (uLen) {
             u.x *= 2 * halfPointSize / uLen;
             u.y *= 2 * halfPointSize / uLen;
@@ -1719,7 +1717,7 @@ void QTriangulator<T>::ComplexToSimple::DebugDialog::paintEvent(QPaintEvent *)
 template <typename T>
 void QTriangulator<T>::ComplexToSimple::DebugDialog::wheelEvent(QWheelEvent *event)
 {
-    qreal scale = exp(-0.001 * event->delta());
+    qreal scale = qExp(-0.001 * event->delta());
     QPointF center = m_window.center();
     QPointF delta = scale * (m_window.bottomRight() - center);
     m_window = QRectF(center - delta, center + delta);
diff --git a/src/gui/painting/qdrawhelper.cpp b/src/gui/painting/qdrawhelper.cpp
index f461dfef06..84063eb692 100644
--- a/src/gui/painting/qdrawhelper.cpp
+++ b/src/gui/painting/qdrawhelper.cpp
@@ -1684,7 +1684,7 @@ static const uint * QT_FASTCALL fetchTransformedBilinearARGB32PM(uint *buffer, c
                     b++;
                     fx += fdx;
                 }
-            } else if ((fdx < 0 && fdx > -(fixed_scale / 8)) || fabs(data->m22) < (1./8.)) { // scale up more than 8x
+            } else if ((fdx < 0 && fdx > -(fixed_scale / 8)) || std::abs(data->m22) < (1./8.)) { // scale up more than 8x
                 int y1 = (fy >> 16);
                 int y2;
                 fetchTransformedBilinear_pixelBounds<blendType>(image_height, image_y1, image_y2, y1, y2);
@@ -1843,7 +1843,7 @@ static const uint * QT_FASTCALL fetchTransformedBilinearARGB32PM(uint *buffer, c
                 }
             }
         } else { //rotation
-            if (fabs(data->m11) > 8 || fabs(data->m22) > 8) {
+            if (std::abs(data->m11) > 8 || std::abs(data->m22) > 8) {
                 //if we are zooming more than 8 times, we use 8bit precision for the position.
                 while (b < end) {
                     int x1 = (fx >> 16);
@@ -2196,7 +2196,7 @@ static const uint *QT_FASTCALL fetchTransformedBilinear(uint *buffer, const Oper
                     layout->convertToARGB32PM(buf1, buf1, len * 2, layout, clut);
                     layout->convertToARGB32PM(buf2, buf2, len * 2, layout, clut);
 
-                    if ((fdx < 0 && fdx > -(fixed_scale / 8)) || fabs(data->m22) < (1./8.)) { // scale up more than 8x
+                    if ((fdx < 0 && fdx > -(fixed_scale / 8)) || std::abs(data->m22) < (1./8.)) { // scale up more than 8x
                         int disty = (fy & 0x0000ffff) >> 8;
                         for (int i = 0; i < len; ++i) {
                             uint tl = buf1[i * 2 + 0];
@@ -2255,7 +2255,7 @@ static const uint *QT_FASTCALL fetchTransformedBilinear(uint *buffer, const Oper
                 layout->convertToARGB32PM(buf1, buf1, len * 2, layout, clut);
                 layout->convertToARGB32PM(buf2, buf2, len * 2, layout, clut);
 
-                if (fabs(data->m11) > 8 || fabs(data->m22) > 8) {
+                if (std::abs(data->m11) > 8 || std::abs(data->m22) > 8) {
                     //if we are zooming more than 8 times, we use 8bit precision for the position.
                     for (int i = 0; i < len; ++i) {
                         uint tl = buf1[i * 2 + 0];
diff --git a/src/gui/painting/qmath_p.h b/src/gui/painting/qmath_p.h
index 50a49c2cb5..9cb64a46cb 100644
--- a/src/gui/painting/qmath_p.h
+++ b/src/gui/painting/qmath_p.h
@@ -45,14 +45,13 @@
 // We mean it.
 //
 
-#include <math.h>
 #include <qmath.h>
 
 QT_BEGIN_NAMESPACE
 
-static const qreal Q_PI   = qreal(3.14159265358979323846);   // pi
-static const qreal Q_2PI  = qreal(6.28318530717958647693);   // 2*pi
-static const qreal Q_PI2  = qreal(1.57079632679489661923);   // pi/2
+static const qreal Q_PI   = qreal(M_PI);     // pi
+static const qreal Q_2PI  = qreal(2 * M_PI); // 2*pi
+static const qreal Q_PI2  = qreal(M_PI_2);   // pi/2
 static const qreal Q_MM_PER_INCH = 25.4;
 
 inline int qIntSqrtInt(int v)
diff --git a/src/gui/painting/qrasterizer.cpp b/src/gui/painting/qrasterizer.cpp
index 426dd846ed..75bf31cde1 100644
--- a/src/gui/painting/qrasterizer.cpp
+++ b/src/gui/painting/qrasterizer.cpp
@@ -712,20 +712,10 @@ static inline bool q26Dot6Compare(qreal p1, qreal p2)
     return int((p2  - p1) * 64.) == 0;
 }
 
-static inline qreal qFloorF(qreal v)
-{
-#ifdef QT_USE_MATH_H_FLOATS
-    if (sizeof(qreal) == sizeof(float))
-        return floorf(v);
-    else
-#endif
-        return floor(v);
-}
-
 static inline QPointF snapTo26Dot6Grid(const QPointF &p)
 {
-    return QPointF(qFloorF(p.x() * 64) * (1 / qreal(64)),
-                   qFloorF(p.y() * 64) * (1 / qreal(64)));
+    return QPointF(std::floor(p.x() * 64) * (1 / qreal(64)),
+                   std::floor(p.y() * 64) * (1 / qreal(64)));
 }
 
 /*
@@ -832,7 +822,7 @@ void QRasterizer::rasterizeLine(const QPointF &a, const QPointF &b, qreal width,
             return;
 
         // adjust width which is given relative to |b - a|
-        width *= sqrt(w0 / w);
+        width *= qSqrt(w0 / w);
     }
 
     QSpanBuffer buffer(d->blend, d->data, d->clipRect);
diff --git a/src/gui/text/qdistancefield.cpp b/src/gui/text/qdistancefield.cpp
index 49ec31fc19..471a39a6e1 100644
--- a/src/gui/text/qdistancefield.cpp
+++ b/src/gui/text/qdistancefield.cpp
@@ -509,8 +509,8 @@ static void makeDistanceField(QDistanceFieldData *data, const QPainterPath &path
         bits[i] = exteriorColor;
 
     const qreal angleStep = qreal(15 * 3.141592653589793238 / 180);
-    const QPoint rotation(qRound(cos(angleStep) * 0x4000),
-                          qRound(sin(angleStep) * 0x4000)); // 2:14 signed
+    const QPoint rotation(qRound(qCos(angleStep) * 0x4000),
+                          qRound(qSin(angleStep) * 0x4000)); // 2:14 signed
 
     const quint32 *indices = pathIndices.data();
     QVarLengthArray<QPoint> normals;
@@ -544,7 +544,7 @@ static void makeDistanceField(QDistanceFieldData *data, const QPainterPath &path
             QPoint n(to.y() - from.y(), from.x() - to.x());
             if (n.x() == 0 && n.y() == 0)
                 continue;
-            int scale = qRound((offs << 16) / sqrt(qreal(n.x() * n.x() + n.y() * n.y()))); // 8:16
+            int scale = qRound((offs << 16) / qSqrt(qreal(n.x() * n.x() + n.y() * n.y()))); // 8:16
             n.rx() = n.x() * scale >> 8;
             n.ry() = n.y() * scale >> 8;
             normals.append(n);
diff --git a/src/gui/text/qfontdatabase.cpp b/src/gui/text/qfontdatabase.cpp
index 211b8b6659..1cdbf6aa8e 100644
--- a/src/gui/text/qfontdatabase.cpp
+++ b/src/gui/text/qfontdatabase.cpp
@@ -2640,7 +2640,7 @@ void QFontDatabase::load(const QFontPrivate *d, int script)
     QFontDef req = d->request;
 
     if (req.pixelSize == -1) {
-        req.pixelSize = floor(((req.pointSize * d->dpi) / 72) * 100 + 0.5) / 100;
+        req.pixelSize = std::floor(((req.pointSize * d->dpi) / 72) * 100 + 0.5) / 100;
         req.pixelSize = qRound(req.pixelSize);
     }
     if (req.pointSize < 0)
diff --git a/src/gui/util/qgridlayoutengine.cpp b/src/gui/util/qgridlayoutengine.cpp
index 5b98001b38..df8dab2903 100644
--- a/src/gui/util/qgridlayoutengine.cpp
+++ b/src/gui/util/qgridlayoutengine.cpp
@@ -193,7 +193,7 @@ namespace {
 // does not return int
 static inline qreal qround(qreal f)
 {
-    return floor(f + 0.5);
+    return std::floor(f + qreal(0.5));
 }
 
 }
@@ -355,7 +355,7 @@ void QGridLayoutRowData::calculateGeometries(int start, int end, qreal targetSiz
                     qreal maxBoxSize = box.q_maximumSize;
 
                     if (snapToPixelGrid)
-                        maxBoxSize = qMax(box.q_minimumSize, floor(maxBoxSize));
+                        maxBoxSize = qMax(box.q_minimumSize, std::floor(maxBoxSize));
 
                     qreal avail = sumCurrentAvailable * factors[i] / sumFactors;
                     if (sizes[i] + avail >= maxBoxSize) {
diff --git a/src/gui/util/qvalidator.cpp b/src/gui/util/qvalidator.cpp
index dcb1f9817f..6b1e20c844 100644
--- a/src/gui/util/qvalidator.cpp
+++ b/src/gui/util/qvalidator.cpp
@@ -40,7 +40,7 @@
 #include "private/qlocale_p.h"
 
 #include <limits.h>
-#include <math.h>
+#include <cmath>
 
 QT_BEGIN_NAMESPACE
 
@@ -384,7 +384,7 @@ static int numDigits(qlonglong n)
 {
     if (n == 0)
         return 1;
-    return (int)log10(double(n)) + 1;
+    return (int)std::log10(double(n)) + 1;
 }
 
 static qlonglong pow10(int exp)
diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index 69bd080477..e461dd0fd4 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -400,8 +400,8 @@ void QGL2PaintEngineExPrivate::updateMatrix()
     // anti-aliased text rendering. In such cases, we snap the translate to the pixel grid.
     if (snapToPixelGrid && transform.type() == QTransform::TxTranslate) {
         // 0.50 needs to rounded down to 0.0 for consistency with raster engine:
-        dx = ceilf(dx - 0.5f);
-        dy = ceilf(dy - 0.5f);
+        dx = std::ceil(dx - 0.5f);
+        dy = std::ceil(dy - 0.5f);
     }
     pmvMatrix[0][0] = (wfactor * transform.m11())  - transform.m13();
     pmvMatrix[1][0] = (wfactor * transform.m21())  - transform.m23();
diff --git a/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm b/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
index 3485c9a558..123a2c4c79 100644
--- a/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
+++ b/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
@@ -39,9 +39,11 @@
 
 #include <private/qimage_p.h>
 
+#include <cmath>
+
 QT_BEGIN_NAMESPACE
 
-static float SYNTHETIC_ITALIC_SKEW = tanf(14 * acosf(0) / 90);
+static float SYNTHETIC_ITALIC_SKEW = std::tan(14.f * std::acos(0.f) / 90.f);
 
 bool QCoreTextFontEngine::ct_getSfntTable(void *user_data, uint tag, uchar *buffer, uint *length)
 {
diff --git a/src/plugins/platforms/cocoa/qpaintengine_mac.mm b/src/plugins/platforms/cocoa/qpaintengine_mac.mm
index 2df4c588cc..16eb281a2f 100644
--- a/src/plugins/platforms/cocoa/qpaintengine_mac.mm
+++ b/src/plugins/platforms/cocoa/qpaintengine_mac.mm
@@ -654,11 +654,11 @@ QCoreGraphicsPaintEngine::updateState(const QPaintEngineState &state)
                 d->cosmeticPenSize = 1.0;
         } else {
             d->cosmeticPen = QCoreGraphicsPaintEnginePrivate::CosmeticSetPenWidth;
-            static const float sqrt2 = sqrt(2);
+            static const float sqrt2 = std::sqrt(2.0f);
             qreal width = d->current.pen.widthF();
             if (!width)
                 width = 1;
-            d->cosmeticPenSize = sqrt(pow(d->pixelSize.y(), 2) + pow(d->pixelSize.x(), 2)) / sqrt2 * width;
+            d->cosmeticPenSize = std::sqrt(std::pow(d->pixelSize.y(), 2) + std::pow(d->pixelSize.x(), 2)) / sqrt2 * width;
         }
     }
 }
diff --git a/src/plugins/platforms/windows/qwindowstabletsupport.cpp b/src/plugins/platforms/windows/qwindowstabletsupport.cpp
index 1818d614fd..7b871be015 100644
--- a/src/plugins/platforms/windows/qwindowstabletsupport.cpp
+++ b/src/plugins/platforms/windows/qwindowstabletsupport.cpp
@@ -455,10 +455,10 @@ bool QWindowsTabletSupport::translateTabletPacketEvent()
             // X Tilt = arctan(X / Z)
             // Y Tilt = arctan(Y / Z)
             const double radAzim = (packet.pkOrientation.orAzimuth / 10.0) * (M_PI / 180);
-            const double tanAlt = tan((abs(packet.pkOrientation.orAltitude / 10.0)) * (M_PI / 180));
+            const double tanAlt = std::tan((std::abs(packet.pkOrientation.orAltitude / 10.0)) * (M_PI / 180));
 
-            const double degX = atan(sin(radAzim) / tanAlt);
-            const double degY = atan(cos(radAzim) / tanAlt);
+            const double degX = std::atan(std::sin(radAzim) / tanAlt);
+            const double degY = std::atan(std::cos(radAzim) / tanAlt);
             tiltX = int(degX * (180 / M_PI));
             tiltY = int(-degY * (180 / M_PI));
             rotation = 360.0 - (packet.pkOrientation.orTwist / 10.0);
diff --git a/src/widgets/widgets/qdial.cpp b/src/widgets/widgets/qdial.cpp
index c9e16205f0..b6ec54997b 100644
--- a/src/widgets/widgets/qdial.cpp
+++ b/src/widgets/widgets/qdial.cpp
@@ -136,9 +136,9 @@ void QDial::initStyleOption(QStyleOptionSlider *option) const
 int QDialPrivate::valueFromPoint(const QPoint &p) const
 {
     Q_Q(const QDial);
-    double yy = (double)q->height()/2.0 - p.y();
-    double xx = (double)p.x() - q->width()/2.0;
-    double a = (xx || yy) ? qAtan2(yy, xx) : 0;
+    double yy = q->height()/2.0 - p.y();
+    double xx = p.x() - q->width()/2.0;
+    double a = (xx || yy) ? std::atan2(yy, xx) : 0;
 
     if (a < Q_PI / -2)
         a = a + Q_PI * 2;