研究这个问题的起因发现使用<=比较时间的不准确，所以怀疑是一个浮点数（Delphi里的time就是一个浮点数）。结果却发现是一个int
class Q_CORE_EXPORT QTime { explicit Q_DECL_CONSTEXPR QTime(int ms) : mds(ms) #if defined(Q_OS_WINCE) , startTick(NullTime) #endif {} public: Q_DECL_CONSTEXPR QTime(): mds(NullTime) #if defined(Q_OS_WINCE) , startTick(NullTime) #endif {} QTime(int h, int m, int s = 0, int ms = 0); Q_DECL_CONSTEXPR bool isNull() const { return mds == NullTime; } bool isValid() const; int hour() const; int minute() const; int second() const; int msec() const; #ifndef QT_NO_DATESTRING QString toString(Qt::DateFormat f = Qt::TextDate) const; QString toString(const QString &format) const; #endif bool setHMS(int h, int m, int s, int ms = 0); QTime addSecs(int secs) const Q_REQUIRED_RESULT; int secsTo(const QTime &) const; QTime addMSecs(int ms) const Q_REQUIRED_RESULT; int msecsTo(const QTime &) const; Q_DECL_CONSTEXPR bool operator==(const QTime &other) const { return mds == other.mds; } Q_DECL_CONSTEXPR bool operator!=(const QTime &other) const { return mds != other.mds; } Q_DECL_CONSTEXPR bool operator< (const QTime &other) const { return mds < other.mds; } Q_DECL_CONSTEXPR bool operator<=(const QTime &other) const { return mds <= other.mds; } Q_DECL_CONSTEXPR bool operator> (const QTime &other) const { return mds > other.mds; } Q_DECL_CONSTEXPR bool operator>=(const QTime &other) const { return mds >= other.mds; } static Q_DECL_CONSTEXPR inline QTime fromMSecsSinceStartOfDay(int msecs) { return QTime(msecs); } Q_DECL_CONSTEXPR inline int msecsSinceStartOfDay() const { return mds == NullTime ? 0 : mds; } static QTime currentTime(); #ifndef QT_NO_DATESTRING static QTime fromString(const QString &s, Qt::DateFormat f = Qt::TextDate); static QTime fromString(const QString &s, const QString &format); #endif static bool isValid(int h, int m, int s, int ms = 0); void start(); int restart(); int elapsed() const; private: enum TimeFlag { NullTime = -1 }; Q_DECL_CONSTEXPR inline int ds() const { return mds == -1 ? 0 : mds; } int mds; #if defined(Q_OS_WINCE) int startTick; #endif friend class QDateTime; friend class QDateTimePrivate; #ifndef QT_NO_DATASTREAM friend Q_CORE_EXPORT QDataStream &operator<<(QDataStream &, const QTime &); friend Q_CORE_EXPORT QDataStream &operator>>(QDataStream &, QTime &); #endif };
但是整数的比较，为什么会不准确呢？不是很理解。。。非得减去一秒之后，比较才准确。让我再想想。。。
看到里面有一个QDateTimePrivate，略加研究之后发现
同时还在qdatetime.h里发现它使用了QDateTimePrivate，搜索之后（不在磁盘上搜索，只能看到它在qdatetime.h里有一个预定义class QDateTimePrivate），发现它定义在
C:QtQt5.6.25.6mingw49_32includeQtCore5.6.2QtCoreprivateqdatetime_p.h
C:QtQt5.6.25.6Srcqtbasesrccorelib oolsqdatetime.cpp
而不存在qdateime_p.cpp文件。
在qdatetime_p.h里发现如下定义：
class QDateTimePrivate : public QSharedData { public: // Never change or delete this enum, it is required for backwards compatible // serialization of QDateTime before 5.2, so is essentially public API enum Spec { LocalUnknown = -1, LocalStandard = 0, LocalDST = 1, UTC = 2, OffsetFromUTC = 3, TimeZone = 4 }; // Daylight Time Status enum DaylightStatus { NoDaylightTime = -2, UnknownDaylightTime = -1, StandardTime = 0, DaylightTime = 1 }; // Status of date/time enum StatusFlag { NullDate = 0x01, NullTime = 0x02, ValidDate = 0x04, // just the date field ValidTime = 0x08, // just the time field ValidDateTime = 0x10, // the whole object (including timezone) SetToStandardTime = 0x40, SetToDaylightTime = 0x80 }; Q_DECLARE_FLAGS(StatusFlags, StatusFlag) QDateTimePrivate() : m_msecs(0), m_spec(Qt::LocalTime), m_offsetFromUtc(0), m_status(NullDate | NullTime) {} QDateTimePrivate(const QDate &toDate, const QTime &toTime, Qt::TimeSpec toSpec, int offsetSeconds); #ifndef QT_BOOTSTRAPPED QDateTimePrivate(const QDate &toDate, const QTime &toTime, const QTimeZone & timeZone); #endif // QT_BOOTSTRAPPED // ### XXX: when the tooling situation improves, look at fixing the padding. // 4 bytes padding qint64 m_msecs; Qt::TimeSpec m_spec; int m_offsetFromUtc; #ifndef QT_BOOTSTRAPPED QTimeZone m_timeZone; #endif // QT_BOOTSTRAPPED StatusFlags m_status; void setTimeSpec(Qt::TimeSpec spec, int offsetSeconds); void setDateTime(const QDate &date, const QTime &time); QPair<QDate, QTime> getDateTime() const; void setDaylightStatus(DaylightStatus status); DaylightStatus daylightStatus() const; // Returns msecs since epoch, assumes offset value is current inline qint64 toMSecsSinceEpoch() const; void checkValidDateTime(); void refreshDateTime(); // Get/set date and time status inline bool isNullDate() const { return m_status & NullDate; } inline bool isNullTime() const { return m_status & NullTime; } inline bool isValidDate() const { return m_status & ValidDate; } inline bool isValidTime() const { return m_status & ValidTime; } inline bool isValidDateTime() const { return m_status & ValidDateTime; } inline void setValidDateTime() { m_status |= ValidDateTime; } inline void clearValidDateTime() { m_status &= ~ValidDateTime; } inline void clearSetToDaylightStatus() { m_status &= ~(SetToStandardTime | SetToDaylightTime); } #ifndef QT_BOOTSTRAPPED static qint64 zoneMSecsToEpochMSecs(qint64 msecs, const QTimeZone &zone, QDate *localDate = 0, QTime *localTime = 0); #endif // QT_BOOTSTRAPPED static inline qint64 minJd() { return QDate::minJd(); } static inline qint64 maxJd() { return QDate::maxJd(); } };
可见的此时又变成了一个qint64，它可能是QDateTime要用到的数据。于是又看了一下qdatetime的定义：
class QDateTimePrivate; class Q_CORE_EXPORT QDateTime { public: QDateTime(); explicit QDateTime(const QDate &); QDateTime(const QDate &, const QTime &, Qt::TimeSpec spec = Qt::LocalTime); // ### Qt 6: Merge with above with default offsetSeconds = 0 QDateTime(const QDate &date, const QTime &time, Qt::TimeSpec spec, int offsetSeconds); #ifndef QT_BOOTSTRAPPED QDateTime(const QDate &date, const QTime &time, const QTimeZone &timeZone); #endif // QT_BOOTSTRAPPED QDateTime(const QDateTime &other); ~QDateTime(); #ifdef Q_COMPILER_RVALUE_REFS QDateTime &operator=(QDateTime &&other) Q_DECL_NOTHROW { swap(other); return *this; } #endif QDateTime &operator=(const QDateTime &other); void swap(QDateTime &other) Q_DECL_NOTHROW { qSwap(d, other.d); } bool isNull() const; bool isValid() const; QDate date() const; QTime time() const; Qt::TimeSpec timeSpec() const; int offsetFromUtc() const; #ifndef QT_BOOTSTRAPPED QTimeZone timeZone() const; #endif // QT_BOOTSTRAPPED QString timeZoneAbbreviation() const; bool isDaylightTime() const; qint64 toMSecsSinceEpoch() const; // ### Qt 6: use quint64 instead of uint uint toTime_t() const; void setDate(const QDate &date); void setTime(const QTime &time); void setTimeSpec(Qt::TimeSpec spec); void setOffsetFromUtc(int offsetSeconds); #ifndef QT_BOOTSTRAPPED void setTimeZone(const QTimeZone &toZone); #endif // QT_BOOTSTRAPPED void setMSecsSinceEpoch(qint64 msecs); // ### Qt 6: use quint64 instead of uint void setTime_t(uint secsSince1Jan1970UTC); #ifndef QT_NO_DATESTRING QString toString(Qt::DateFormat f = Qt::TextDate) const; QString toString(const QString &format) const; #endif QDateTime addDays(qint64 days) const Q_REQUIRED_RESULT; QDateTime addMonths(int months) const Q_REQUIRED_RESULT; QDateTime addYears(int years) const Q_REQUIRED_RESULT; QDateTime addSecs(qint64 secs) const Q_REQUIRED_RESULT; QDateTime addMSecs(qint64 msecs) const Q_REQUIRED_RESULT; QDateTime toTimeSpec(Qt::TimeSpec spec) const; inline QDateTime toLocalTime() const { return toTimeSpec(Qt::LocalTime); } inline QDateTime toUTC() const { return toTimeSpec(Qt::UTC); } QDateTime toOffsetFromUtc(int offsetSeconds) const; #ifndef QT_BOOTSTRAPPED QDateTime toTimeZone(const QTimeZone &toZone) const; #endif // QT_BOOTSTRAPPED qint64 daysTo(const QDateTime &) const; qint64 secsTo(const QDateTime &) const; qint64 msecsTo(const QDateTime &) const; bool operator==(const QDateTime &other) const; inline bool operator!=(const QDateTime &other) const { return !(*this == other); } bool operator<(const QDateTime &other) const; inline bool operator<=(const QDateTime &other) const { return !(other < *this); } inline bool operator>(const QDateTime &other) const { return other < *this; } inline bool operator>=(const QDateTime &other) const { return !(*this < other); } #if QT_DEPRECATED_SINCE(5, 2) QT_DEPRECATED void setUtcOffset(int seconds); QT_DEPRECATED int utcOffset() const; #endif // QT_DEPRECATED_SINCE static QDateTime currentDateTime(); static QDateTime currentDateTimeUtc(); #ifndef QT_NO_DATESTRING static QDateTime fromString(const QString &s, Qt::DateFormat f = Qt::TextDate); static QDateTime fromString(const QString &s, const QString &format); #endif // ### Qt 6: use quint64 instead of uint static QDateTime fromTime_t(uint secsSince1Jan1970UTC); // ### Qt 6: Merge with above with default spec = Qt::LocalTime static QDateTime fromTime_t(uint secsSince1Jan1970UTC, Qt::TimeSpec spec, int offsetFromUtc = 0); #ifndef QT_BOOTSTRAPPED static QDateTime fromTime_t(uint secsSince1Jan1970UTC, const QTimeZone &timeZone); #endif static QDateTime fromMSecsSinceEpoch(qint64 msecs); // ### Qt 6: Merge with above with default spec = Qt::LocalTime static QDateTime fromMSecsSinceEpoch(qint64 msecs, Qt::TimeSpec spec, int offsetFromUtc = 0); #ifndef QT_BOOTSTRAPPED static QDateTime fromMSecsSinceEpoch(qint64 msecs, const QTimeZone &timeZone); #endif static qint64 currentMSecsSinceEpoch() Q_DECL_NOTHROW; #if defined(Q_OS_MAC) || defined(Q_QDOC) static QDateTime fromCFDate(CFDateRef date); CFDateRef toCFDate() const Q_DECL_CF_RETURNS_RETAINED; # if defined(__OBJC__) || defined(Q_QDOC) static QDateTime fromNSDate(const NSDate *date); NSDate *toNSDate() const Q_DECL_NS_RETURNS_AUTORELEASED; # endif #endif private: friend class QDateTimePrivate; // ### Qt6: Using a private here has high impact on runtime // on users such as QFileInfo. In Qt 6, the data members // should be inlined. QSharedDataPointer<QDateTimePrivate> d; #ifndef QT_NO_DATASTREAM friend Q_CORE_EXPORT QDataStream &operator<<(QDataStream &, const QDateTime &); friend Q_CORE_EXPORT QDataStream &operator>>(QDataStream &, QDateTime &); #endif #if !defined(QT_NO_DEBUG_STREAM) && !defined(QT_NO_DATESTRING) friend Q_CORE_EXPORT QDebug operator<<(QDebug, const QDateTime &); #endif }; Q_DECLARE_SHARED(QDateTime)
其中最关键的是<操作符的比较，它代表了使用的真正数据，而且其它几个比较函数实质上都依赖这个操作符：
bool QDateTime::operator<(const QDateTime &other) const { if (d->m_spec == Qt::LocalTime && other.d->m_spec == Qt::LocalTime && d->m_status == other.d->m_status) { return (d->m_msecs < other.d->m_msecs); } // Convert to UTC and compare return (toMSecsSinceEpoch() < other.toMSecsSinceEpoch()); }
其中最关键的是toMSecsSinceEpoch函数，结果发现如下定义：
qint64 toMSecsSinceEpoch() const;
可见的QDateTime本质上是一个qint64