我有以下代码
#include <QDebug> //Needed for other stuff!!
#include <QDataStream>
class TestClass {
public:
class SubClass {
public:
QString a;
int b;
/*
//Needed for QDataStream but not relevant for the generated error
friend QDataStream& operator<<(QDataStream& os, SubClass const& f)
{
os << f.a;
os << f.b;
return os;
}
friend QDataStream& operator>>(QDataStream& is, SubClass& f)
{
is >> f.a;
is >> f.b;
return is;
}*/
friend QDataStream& operator<< <SubClass>(QDataStream&, QList<SubClass> const&);
friend QDataStream& operator>> <SubClass>(QDataStream&, QList<SubClass>&);
};
};
用 qt5.5 编译它会给我以下错误:
/usr/include/qt/QtCore/qflags.h:88: error: invalid application of 'sizeof' to an incomplete type 'TestClass::SubClass'
Q_STATIC_ASSERT_X((sizeof(Enum) <= sizeof(int)),
^~~~~~~~~~~~
/usr/include/qt/QtCore/qtypetraits.h:478: error: 'TestClass::SubClass' is an incomplete type
: integral_constant<bool, (T(0) < T(-1))> {};
^
/usr/include/qt/QtCore/qdebug.h:279: in instantiation of template class 'QtPrivate::IsQEnumHelper<QFlags<TestClass::SubClass> >' requested here
QtPrivate::IsQEnumHelper<T>::Value || QtPrivate::IsQEnumHelper<QFlags<T> >::Value,
^
main.cpp:25: while substituting explicitly-specified template arguments into function template 'operator<<'
friend QDataStream& operator<< <SubClass>(QDataStream&, QList<SubClass> const&);
^
其原因似乎在于 QDebug 头文件 (qdebug.h:277) 的以下代码:
template <class T>
inline typename QtPrivate::QEnableIf<
QtPrivate::IsQEnumHelper<T>::Value || QtPrivate::IsQEnumHelper<QFlags<T> >::Value,
QDebug>::Type
operator<<(QDebug debug, const QFlags<T> &flags)
{
//...
}
使用 qt5.4 编译可以正常工作。取了正确的模板函数(qdatastream.h:241)
template <typename T>
QDataStream& operator<<(QDataStream& s, const QList<T>& l)
{
//...
}
问题:
- 我想知道为什么要考虑 qdebug.h 中的模板。我有一些想法,但是带有与 c++ 标准的适当链接和正确解释的答案会很好。
- 是否有解决方法或者我应该向 qt 提交错误报告?