Custom Widget compilation problem

[swhweng]

Hello dear developers/specialists/coders/programers.
How are you doing?
I develop custom applications for major platforms and I use QSwitch widget from
[url]http://qt-apps.org/content/show.php/QSwitch?content=72481[/url]
that is inherited from QWidget and uses <QtDesigner/QDesignerExportWidget>
@class QDESIGNER_WIDGET_EXPORT QSwitch : public QWidget
{...}@
I put it to ui generated from Qt Designer at Qt Designer ( QSwitch plugin added to it ),
in Ubuntu I compile my project with that widget well , but on Windows I get the following errors each time compiler meets QSwitch instances:

./release\mainwindow.o:mainwindow.cpp:(.text+0x2c6a6): undefined reference to _imp___ZN7QSwitch8setValueEb' ./release\mainwindow.o:mainwindow.cpp:(.text+0x56b5a): undefined reference to _imp___ZN7QSwitch8setValueEb'
./release\mainwindow.o:mainwindow.cpp:(.text+0x56c2e): undefined reference to _imp___ZN7QSwitch8setValueEb' ./release\mainwindow.o:mainwindow.cpp:(.text+0x57023): undefined reference to _imp___ZN7QSwitch8setValueEb'
./release\mainwindow.o:mainwindow.cpp:(.text+0x5707f): undefined reference to _imp___ZN7QSwitch8setValueEb' ./release\mainwindow.o:mainwindow.cpp:(.text+0x5723c): more undefined references to _imp___ZN7QSwitch8setValueEb' follow
./release\mainwindow.o:mainwindow.cpp:(.text$_ZN14Ui_MainControl7setupUiEP11QMainWindow[Ui_MainControl::setupUi(QMainWindow*)]+0xa2e2): undefined reference to _imp___ZN7QSwitchC1EP7QWidget' ./release\mainwindow.o:mainwindow.cpp:(.text$_ZN14Ui_MainControl7setupUiEP11QMainWindow[Ui_MainControl::setupUi(QMainWindow*)]+0xb5b5): undefined reference to _imp___ZN7QSwitch8setValueEb'
./release\mainwindow.o:mainwindow.cpp:(.text$_ZN14Ui_MainControl7setupUiEP11QMainWindow[Ui_MainControl::setupUi(QMainWindow*)]+0xb5fa): undefined reference to _imp___ZN7QSwitch7setTypeENS_10SwitchTypeE' ./release\qswitch.o:qswitch.cpp:(.text+0x4f): undefined reference to _imp___ZN7QSwitch12valueChangedEb'
./release\qswitch.o:qswitch.cpp:(.text+0x79): undefined reference to _imp___ZN7QSwitch12valueChangedEb' ./release\qswitch.o:qswitch.cpp:(.text+0xdd): undefined reference to _imp___ZTV7QSwitch'
./release\qswitch.o:qswitch.cpp:(.text+0x169): undefined reference to _imp___ZTV7QSwitch' ./release\moc_qswitch.o:moc_qswitch.cpp:(.text+0x15): undefined reference to _imp___ZN7QSwitch16staticMetaObjectE'
./release\moc_qswitch.o:moc_qswitch.cpp:(.text+0x26): undefined reference to _imp___ZN7QSwitch16staticMetaObjectE' ./release\moc_qswitch.o:moc_qswitch.cpp:(.text+0x59): undefined reference to _imp___ZN7QSwitch16staticMetaObjectE'
./release\moc_qswitch.o:moc_qswitch.cpp:(.text+0xc3): undefined reference to _imp___ZN7QSwitch11toggleValueEv' ./release\moc_qswitch.o:moc_qswitch.cpp:(.text+0x11d): undefined reference to _imp___ZN7QSwitch7setTypeENS_10SwitchTypeE'
./release\moc_qswitch.o:moc_qswitch.cpp:(.text+0x151): undefined reference to _imp___ZN7QSwitch7setTypeENS_10SwitchTypeE' ./release\moc_qswitch.o:moc_qswitch.cpp:(.text+0x16e): undefined reference to _imp___ZN7QSwitch8setValueEb'
./release\moc_qswitch.o:moc_qswitch.cpp:(.text+0x1c7): undefined reference to `_imp___ZN7QSwitch8setValueEb'
collect2: ld returned 1 exit status

Please help: Why such errors does anybody know? What is wrong/unclear? How to successfully compile on Windows ui with QSwitch widget?
Thanks.

[swhweng]

...I've solved the problem now by removing @QDESIGNER_WIDGET_EXPORT@ macro and @#include <QtDesigner/QDesignerExportWidget>@ in the qswitch.h.

[swhweng]

But...,perhaps it will be interesting, why on Windows it can't be compiled with the macro?

[ZapB]

It is because MS compiler uses symbol visibility rules by default (ie it only exports those symbols that you tell it to). Whereas with GCC you have to explicitly enable this feature by using

@
CONFIG += hide_symbols
@

If you add the above to your .pro file it will also fail to link on Linux due to unexported symbols. We use this as it reduces the number of symbols exported in our libs and hence slightly improves application start up time and keeps the private parts of our API private.