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Qt信号参数中使用QVariantList时编译问题_(reinterpret_cast(current))->~t();

作者：繁依Fanyi0 | 2024-02-20 23:41:13

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(reinterpret_cast(current))->~t();

今天调试代码时遇到一个奇怪的问题，不过一般感觉比较奇怪的问题，最后查到原因时，原因都比较简单！

编译问题

先来看一下qt的编译错误，提示一堆错误:

  1. In file included from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qglobal.h:1173:0,
  2.                  from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qnamespace.h:43,
  3.                  from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qobjectdefs.h:48,
  4.                  from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/qobject.h:46,
  5.                  from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/QObject:1,
  6.                  from temp\moc\../../../test/module_function/test.h:4,
  7.                  from temp\moc\moc_test.cpp:9:
  8. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qtypeinfo.h: In instantiation of 'class QTypeInfo<QVariant>':
  9. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qlist.h:459:31:   required from 'void QList<T>::node_copy(QList<T>::Node*, QList<T>::Node*, QList<T>::Node*) [with T = QVariant]'
  10. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qlist.h:813:22:   required from 'QList<T>::QList(const QList<T>&) [with T = QVariant]'
  11. temp\moc\moc_test.cpp:103:82:   required from here
  12. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qtypeinfo.h:67:26: error: invalid application of 'sizeof' to incomplete type 'QVariant'
  13.          isLarge = (sizeof(T)>sizeof(void*)),
  14.                           ^
  15. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qtypeinfo.h:69:24: error: invalid application of 'sizeof' to incomplete type 'QVariant'
  16.          sizeOf = sizeof(T)
  17.                         ^
  18. In file included from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/qobject.h:49:0,
  19.                  from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/QObject:1,
  20.                  from temp\moc\../../../test/module_function/test.h:4,
  21.                  from temp\moc\moc_test.cpp:9:
  22. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qlist.h: In instantiation of 'void QList<T>::node_copy(QList<T>::Node*, QList<T>::Node*, QList<T>::Node*) [with T = QVariant]':
  23. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qlist.h:813:22:   required from 'QList<T>::QList(const QList<T>&) [with T = QVariant]'
  24. temp\moc\moc_test.cpp:103:82:   required from here
  25. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qlist.h:462:28: error: invalid use of incomplete type 'class QVariant'
  26.                  current->v = new T(*reinterpret_cast<T*>(src->v));
  27.                             ^
  28. In file included from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/qobject.h:54:0,
  29.                  from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/QObject:1,
  30.                  from temp\moc\../../../test/module_function/test.h:4,
  31.                  from temp\moc\moc_test.cpp:9:
  32. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qmetatype.h:114:21: note: forward declaration of 'class QVariant'
  33.      F(QVariant, 41, QVariant) \
  34.                      ^
  35. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qmetatype.h:1924:11: note: in definition of macro 'QT_FORWARD_DECLARE_STATIC_TYPES_ITER'
  36.      class Name;
  37.            ^
  38. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qmetatype.h:1926:1: note: in expansion of macro 'QT_FOR_EACH_STATIC_CORE_CLASS'
  39.  QT_FOR_EACH_STATIC_CORE_CLASS(QT_FORWARD_DECLARE_STATIC_TYPES_ITER)
  40.  ^
  41. In file included from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/qobject.h:49:0,
  42.                  from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/QObject:1,
  43.                  from temp\moc\../../../test/module_function/test.h:4,
  44.                  from temp\moc\moc_test.cpp:9:
  45. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qlist.h:468:17: warning: possible problem detected in invocation of delete operator: [-Wdelete-incomplete]
  46.                  delete reinterpret_cast<T*>(current->v);
  47.                  ^
  48. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qlist.h:468:17: warning: invalid use of incomplete type 'class QVariant'
  49. In file included from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/qobject.h:54:0,
  50.                  from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/QObject:1,
  51.                  from temp\moc\../../../test/module_function/test.h:4,
  52.                  from temp\moc\moc_test.cpp:9:
  53. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qmetatype.h:114:21: note: forward declaration of 'class QVariant'
  54.      F(QVariant, 41, QVariant) \
  55.                      ^
  56. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qmetatype.h:1924:11: note: in definition of macro 'QT_FORWARD_DECLARE_STATIC_TYPES_ITER'
  57.      class Name;
  58.            ^
  59. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qmetatype.h:1926:1: note: in expansion of macro 'QT_FOR_EACH_STATIC_CORE_CLASS'
  60.  QT_FOR_EACH_STATIC_CORE_CLASS(QT_FORWARD_DECLARE_STATIC_TYPES_ITER)
  61.  ^
  62. In file included from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/qobject.h:49:0,
  63.                  from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/QObject:1,
  64.                  from temp\moc\../../../test/module_function/test.h:4,
  65.                  from temp\moc\moc_test.cpp:9:
  66. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qlist.h:468:17: note: neither the destructor nor the class-specific operator delete will be called, even if they are declared when the class is defined
  67.                  delete reinterpret_cast<T*>(current->v);
  68.                  ^
  69. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qlist.h:475:17: error: invalid use of incomplete type 'class QVariant'
  70.                  new (current) T(*reinterpret_cast<T*>(src));
  71.                  ^
  72. In file included from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/qobject.h:54:0,
  73.                  from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/QObject:1,
  74.                  from temp\moc\../../../test/module_function/test.h:4,
  75.                  from temp\moc\moc_test.cpp:9:
  76. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qmetatype.h:114:21: note: forward declaration of 'class QVariant'
  77.      F(QVariant, 41, QVariant) \
  78.                      ^
  79. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qmetatype.h:1924:11: note: in definition of macro 'QT_FORWARD_DECLARE_STATIC_TYPES_ITER'
  80.      class Name;
  81.            ^
  82. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qmetatype.h:1926:1: note: in expansion of macro 'QT_FOR_EACH_STATIC_CORE_CLASS'
  83.  QT_FOR_EACH_STATIC_CORE_CLASS(QT_FORWARD_DECLARE_STATIC_TYPES_ITER)
  84.  ^
  85. In file included from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/qobject.h:49:0,
  86.                  from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/QObject:1,
  87.                  from temp\moc\../../../test/module_function/test.h:4,
  88.                  from temp\moc\moc_test.cpp:9:
  89. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qlist.h:481:17: error: invalid use of incomplete type 'class QVariant'
  90.                  (reinterpret_cast<T*>(current))->~T();
  91.                  ^
  92. In file included from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/qobject.h:54:0,
  93.                  from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/QObject:1,
  94.                  from temp\moc\../../../test/module_function/test.h:4,
  95.                  from temp\moc\moc_test.cpp:9:
  96. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qmetatype.h:114:21: note: forward declaration of 'class QVariant'
  97.      F(QVariant, 41, QVariant) \
  98.                      ^
  99. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qmetatype.h:1924:11: note: in definition of macro 'QT_FORWARD_DECLARE_STATIC_TYPES_ITER'
  100.      class Name;
  101.            ^
  102. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qmetatype.h:1926:1: note: in expansion of macro 'QT_FOR_EACH_STATIC_CORE_CLASS'
  103.  QT_FOR_EACH_STATIC_CORE_CLASS(QT_FORWARD_DECLARE_STATIC_TYPES_ITER)
  104.  ^
  105. In file included from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/qobject.h:49:0,
  106.                  from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/QObject:1,
  107.                  from temp\moc\../../../test/module_function/test.h:4,
  108.                  from temp\moc\moc_test.cpp:9:
  109. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qlist.h: In instantiation of 'void QList<T>::node_destruct(QList<T>::Node*, QList<T>::Node*) [with T = QVariant]':
  110. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qlist.h:865:18:   required from 'void QList<T>::dealloc(QListData::Data*) [with T = QVariant]'
  111. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qlist.h:827:16:   required from 'QList<T>::~QList() [with T = QVariant]'
  112. temp\moc\moc_test.cpp:103:82:   required from here
  113. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qlist.h:494:31: warning: possible problem detected in invocation of delete operator: [-Wdelete-incomplete]
  114.          while(from != to) --to, delete reinterpret_cast<T*>(to->v);
  115.                                ^
  116. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qlist.h:494:31: warning: invalid use of incomplete type 'class QVariant'
  117. In file included from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/qobject.h:54:0,
  118.                  from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/QObject:1,
  119.                  from temp\moc\../../../test/module_function/test.h:4,
  120.                  from temp\moc\moc_test.cpp:9:
  121. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qmetatype.h:114:21: note: forward declaration of 'class QVariant'
  122.      F(QVariant, 41, QVariant) \
  123.                      ^
  124. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qmetatype.h:1924:11: note: in definition of macro 'QT_FORWARD_DECLARE_STATIC_TYPES_ITER'
  125.      class Name;
  126.            ^
  127. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qmetatype.h:1926:1: note: in expansion of macro 'QT_FOR_EACH_STATIC_CORE_CLASS'
  128.  QT_FOR_EACH_STATIC_CORE_CLASS(QT_FORWARD_DECLARE_STATIC_TYPES_ITER)
  129.  ^
  130. In file included from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/qobject.h:49:0,
  131.                  from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/QObject:1,
  132.                  from temp\moc\../../../test/module_function/test.h:4,
  133.                  from temp\moc\moc_test.cpp:9:
  134. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qlist.h:494:31: note: neither the destructor nor the class-specific operator delete will be called, even if they are declared when the class is defined
  135.          while(from != to) --to, delete reinterpret_cast<T*>(to->v);
  136.                                ^
  137. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qlist.h:496:32: error: invalid use of incomplete type 'class QVariant'
  138.          while (from != to) --to, reinterpret_cast<T*>(to)->~T();
  139.                                 ^
  140. In file included from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/qobject.h:54:0,
  141.                  from D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include\QtCore/QObject:1,
  142.                  from temp\moc\../../../test/module_function/test.h:4,
  143.                  from temp\moc\moc_test.cpp:9:
  144. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qmetatype.h:114:21: note: forward declaration of 'class QVariant'
  145.      F(QVariant, 41, QVariant) \
  146.                      ^
  147. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qmetatype.h:1924:11: note: in definition of macro 'QT_FORWARD_DECLARE_STATIC_TYPES_ITER'
  148.      class Name;
  149.            ^
  150. D:\Qt\Qt5.10.0\5.10.0\mingw53_32\include/QtCore/qmetatype.h:1926:1: note: in expansion of macro 'QT_FOR_EACH_STATIC_CORE_CLASS'
  151.  QT_FOR_EACH_STATIC_CORE_CLASS(QT_FORWARD_DECLARE_STATIC_TYPES_ITER)
  152.  ^
  153. Makefile.Debug:3709: recipe for target 'temp/obj/moc_test.o' failed
  154. mingw32-make[1]: Leaving directory 'E:/code/test-Debug'
  155. Makefile:36: recipe for target 'debug' failed
  156. mingw32-make[1]: *** [temp/obj/moc_test.o] Error 1
  157. mingw32-make: *** [debug] Error 2
  158. 18:04:40: 进程"D:\Qt\Qt5.10.0\Tools\mingw530_32\bin\mingw32-make.exe"退出，退出代码 2 。
  159. Error while building/deploying project test (kit: Desktop Qt 5.10.0 MinGW 32bit)
  160. When executing step "Make"

排查问题

从这里面可以看出，基本上是与QVariant类型的使用有关系，查了下代码，里面没有直接使用QVariant类型的地方，到是有一个信号的参数类型，使用的是QVariantList，怀疑有可能是这个信号引起的，把这信号注释掉之后，编译不在报错。然后类里面的成员变量里使用QVariantList定义的成员变量，则不会导致这个编译错误！

另外，通过查看编译错误，可以发现，是编译moc_test.cpp文件时开始报错的，也就是说，在编译moc文件时提示报错，moc文件里第9行是#include " temp\moc\../../../test/module_function/test.h"，引用的是测试类的头文件，也看不出什么错误。

只是尝试给test.h里加了个头文件引用：#include <QVariantList>，再次编译错误没有了，编译通过！

 

问题原因

使用QVariantList作为信号的参数时，一定引用头文件：

#include  <QVariantList>

否则会编译错误，如果不作为信号的参数，只是作为成员变量用，或者成员函数的参数，不引用其头文件也不会报错。

这两种情况编译是有点区别的，moc文件是qt编译器根据类源文件自动生成的代码。

 

在此记录一下，以免以后调试遇到同样的问题而浪费时间。

 

 

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