Details
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Bug
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Resolution: Done
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P4: Low
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4.8.6
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None
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Windows 7 Pro x64, VS2010
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4dc597d96c26445a892cfc8f10d0f1da3d8decf1
Description
When using
#include <QtCore> or #include QtXml and having defined
_USE_MATH_DEFINES a warning is triggered by Visual Studio 2010:
c:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\INCLUDE\math.h(632) : warning C4005: 'M_PI' : macro redefinition with the hint: qmath.h(261) : see previous definition of 'M_PI'
In qmath.h you can find at the end of the file:
#ifndef M_PI
#define M_PI (3.14159265358979323846)
#endif
inline qreal qFastSin(qreal x)
{
int si = int(x * (0.5 * QT_SINE_TABLE_SIZE / M_PI)); // Would be more accurate with qRound, but slower.
qreal d = x - si * (2.0 * M_PI / QT_SINE_TABLE_SIZE);
int ci = si + QT_SINE_TABLE_SIZE / 4;
si &= QT_SINE_TABLE_SIZE - 1;
ci &= QT_SINE_TABLE_SIZE - 1;
return qt_sine_table[si] + (qt_sine_table[ci] - 0.5 * qt_sine_table[si] * d) * d;
}
inline qreal qFastCos(qreal x)
{
int ci = int(x * (0.5 * QT_SINE_TABLE_SIZE / M_PI)); // Would be more accurate with qRound, but slower.
qreal d = x - ci * (2.0 * M_PI / QT_SINE_TABLE_SIZE);
int si = ci + QT_SINE_TABLE_SIZE / 4;
si &= QT_SINE_TABLE_SIZE - 1;
ci &= QT_SINE_TABLE_SIZE - 1;
return qt_sine_table[si] - (qt_sine_table[ci] + 0.5 * qt_sine_table[si] * d) * d;
}
QT_END_NAMESPACE
QT_END_HEADER
#endif // QMATH_H
On the one had it is nice to have M_PI defined, but on the other hand math.h defines many additional math constants, too:
#define M_E 2.71828182845904523536 #define M_LOG2E 1.44269504088896340736 #define M_LOG10E 0.434294481903251827651 #define M_LN2 0.693147180559945309417 #define M_LN10 2.30258509299404568402 #define M_PI 3.14159265358979323846 #define M_PI_2 1.57079632679489661923 #define M_PI_4 0.785398163397448309616 #define M_1_PI 0.318309886183790671538 #define M_2_PI 0.636619772367581343076 #define M_2_SQRTPI 1.12837916709551257390 #define M_SQRT2 1.41421356237309504880 #define M_SQRT1_2 0.707106781186547524401
that or not part of qmath.h.
May it be, that the include order in QtCore and QtXml should be changed, to include the math.h before qmath.h, so that M_PI is (optionally) already defined, when qmath.h is included?