Hi everyone, I have a library that export a class that derive from QObject, The class is called 'nonceFinder'. The class use Q_OBJECT macro on its declaration because uses QT signals. The library compiles well for ubuntu, windows, macos for static library and shared library. Then I have another library called 'qclient' that uses the previous library 'nonceFinder'. The compilation of 'qclient' works for ubuntu, macos for shared and static library, and for windows static library, but fails for windows shared library. The error that gives is : qclient.cpp.obj : error LNK2019: unresolved external symbol "public: static struct QMetaObject const qiota::qpow::nonceFinder::staticMetaObject" (?staticMetaObject@nonceFinder@qpow@qiota@@2UQMetaObject@@B) referenced in function "public: static class QMetaObject::Connection __cdecl QObject::connect<void (__cdecl qiota::qpow::nonceFinder::*)(void),class `public: __cdecl `public: __cdecl `public: void __cdecl qiota::Client::send_block(class qiota::qblocks::Block const &)'::`2'::<lambda_2>::operator()(void)const '::`2'::<lambda_1>::operator()(void)const '::`5'::<lambda_2> >(class qiota::qpow::nonceFinder const *,void (__cdecl qiota::qpow::nonceFinder::*)(void),class QObject const *,class `public: __cdecl `public: __cdecl `public: void __cdecl qiota::Client::send_block(class qiota::qblocks::Block const &)'::`2'::<lambda_2>::operator()(void)const '::`2'::<lambda_1>::operator()(void)const '::`5'::<lambda_2>,enum Qt::ConnectionType)" (??$connect@P8nonceFinder@qpow@qiota@@EAAXXZV<lambda_2>@?4???R<lambda_1>@?1???R4?1??send_block@Client@3@QEAAXAEBVBlock@qblocks@3@@Z@QEBA@XZ@QEBA@XZ@@QObject@@SA?AVConnection@QMetaObject@@PEBVnonceFinder@qpow@qiota@@P8345@EAAXXZPEBV0@V<lambda_2>@?4???R<lambda_1>@?1???R6?1??send_block@Client@5@QEAAXAEBVBlock@qblocks@5@@Z@QEBA@XZ@QEBA@XZ@W4ConnectionType@Qt@@@Z) I have check is a problem with Methods like metaObject(), qt_metacall(), qt_metacast(), etc, are defined in the generated moc_ files. So the cause of the unresolved external symbol error is that the moc_ files are not compiled/linked to the project. If, in Visual Studio, deleting and reinserting Q_OBJECT does not work, check that the moc_ files are correctly generated and included in the project. I have also try https://doc.qt.io/qt-6/sharedlibrary.html macros. I use CMake, i do not understand when should I use : Q_DECL_EXPORT - Should be at compilation time of the library? Q_DECL_IMPORT - Should be at linking time of the client and the shared library? Also if i am compiling a static libraries can i keep Q_DECL_IMPORT in my class declaration? If you have managed to compile a shared library on Windows that uses MOC generated sources I will appreciate your help on this. If you now how to set this on CMake better.

I did not see (and not use by myself) qt_standard_project_setup() so you're correct with the automoc. You use the same define for the export definition for both libraries - how should this work?

But there is no shared libary at all nor import/export macros.

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Shared library on windows fails when using moc

Solved General and Desktop

41 Posts 4 Posters 10.9k Views

C Christian Ehrlicher
7 Jun 2023, 18:59

I did not see (and not use by myself) qt_standard_project_setup() so you're correct with the automoc.

You use the same define for the export definition for both libraries - how should this work?
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Mesrine

wrote on 7 Jun 2023, 19:06 last edited by Mesrine 6 Jul 2023, 19:25

#41

@Christian-Ehrlicher
Thats a good point. Thanks!
Using the same definition for both libraries if not included correctly the headers could define the export on the symbol that should have an import statement.

This is not completely clear to me so Let me try.
I let you know :).

Yes, that was the problem. Many thanks.
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M Mesrine has marked this topic as solved on 7 Jun 2023, 19:22

41/41

7 Jun 2023, 19:06