Visual Studio 2017 unresolved external symbol struct QStaticPlugin

azaclauson

I'm attempting to build a project that relies on Qt. I'm most of the way there and have one last unresolved symbol related to Qt plugins, error message below.

I'm using qt-everywhere-opensource-src-5.9.1.zip and as I need to build x86 I'm linking against the .lib files in the msvc2015\lib directory. I've added qtmain.lib, Qt5Core.lib, Qt5Widgets.lib, Qt5Gui.lib and Qt5Network.lib. Search results I need to also link against Qt5PlatformSupport.lib and/or qwindows.lib but neither of those libraries are available. Is there a different mechanism required to link for a Qt static plugin? Note I'm still trying to build so I haven't hit the more common problem of not being able to locate the plugin dll's.

Severity Code Description Project File Line Suppression State
Error LNK2001 unresolved external symbol "struct QStaticPlugin const __cdecl qt_static_plugin_QWindowsIntegrationPlugin(void)" (?qt_static_plugin_QWindowsIntegrationPlugin@@YA?BUQStaticPlugin@@XZ) bitcoin-qt F:\Dev\github\sipsorcery_bitcoin\contrib\msvc\bitcoin-qt\bitcoin.obj 1

kshegunov

@azaclauson said in Visual Studio 2017 unresolved external symbol struct QStaticPlugin:

Is there a different mechanism required to link for a Qt static plugin?

Not for linking, no. You should be able to find those libraries in the plugins directory of your build (I think they were in <QtDir>plugins/platforms). You also might need to initialize each of the plugins manually in code as you're linking static:

#include <QtPlugin>

Q_IMPORT_PLUGIN(QWindowsIntegrationPlugin)
Q_IMPORT_PLUGIN(qjpeg)
// ... etc.

More info here.

azaclauson

Not for linking, no. You should be able to find those libraries in the plugins directory of your build (I think they were in <QtDir>plugins/platforms). You also might need to initialize each of the plugins manually in code as you're linking static:

If I've understood correctly the default Qt downloads available at https://www1.qt.io/download-open-source/#section-2 are built with shared rather than static plugins. In order to get Qt with static plugins I need to do a custom build with the "-static" parameter specified for configure.bat?

That leaves me in a chicken and egg situation. I've been unable to get very far with building Qt either from the git repo or from the above download (if anyone has a configure command that works with the Visual Studio 2017 command prompt I'd be very grateful). I can't make changes to the consumer project I'm attempting to build so need to stick with static plugins.

kshegunov

@azaclauson said in Visual Studio 2017 unresolved external symbol struct QStaticPlugin:

If I've understood correctly the default Qt downloads available at https://www1.qt.io/download-open-source/#section-2 are built with shared rather than static plugins.

I believe so.

In order to get Qt with static plugins I need to do a custom build with the "-static" parameter specified for configure.bat?

That'd be implied if the installer provides only a shared library build.

I've been unable to get very far with building Qt either from the git repo or from the above download (if anyone has a configure command that works with the Visual Studio 2017 command prompt I'd be very grateful).

I suggest you open a new topic for that specifically and provide the configure command you had tried, what was the output and what didn't work.