[Interest] Problem creating a dll that loads static Qt libraries (in mingw) -> final chapter

[Andreas Pakulat]

On 20.01.12 10:14:09, erick oliveira da silva wrote:
> Hi Till,
> 
> Thanks for your reply. I learned a lot with it.
> 
> I compiled qt library by myself. I download the sources and compiled with
> gcc-mingw, the same compiler I am trying to build my simple qt shared
> library now.
> 
> The function that I would like to export:
> 
> --- Header : dllfct.h ---------------------------------
> 
> #ifndef DLLFCT_H
> #define DLLFCT_H
> 
> #include <QtCore/qglobal.h>
> #include <QtGlobal>
> 
> #if defined(MY_DLL)
> #define EXPORT  Q_DECL_EXPORT
> #else
> #define EXPORT  Q_DECL_IMPORT
> #endif
> 
> // function to be imported/exported
> EXPORT void tstfunc (void);
> 
> #endif //DLLFCT_H
> 
> -----------------------------------------------------
> 
> -- Source File : dllfct.cpp ---------------
> 
> #include <QString>
> #include <QDebug>
> #include "dllfct.h"
> 
> void tstfunc (void)
> {
> QString msg = "Hello";
>   qDebug(qPrintable(msg));
> }
> 
> ---------------------------------------------------------
> 
> -- Pro file:
> 
> QT -= gui
> TEMPLATE = lib
> CONFIG += qt dll release
> 
> SOURCES = dllfct.cpp
> 
> MAKEFILE = Make_QDECL
> 
> DEFINES += MY_DLL
> 
> INCLUDEPATH += ./dllQDECL
> DEPENDPATH += ./dllQDECL
> 
> HEADERS = dllfct.h
> 
> --------------------------------
> 
> and here my output:
> 
> D:\dllmingw\qt>mingw32-make -f Make_QDECL.Release
> g++ -c -O2 -frtti -fno-exceptions -Wall -DUNICODE -DQT_LARGEFILE_SUPPORT
> -DMY_DL
> L -DQT_DLL -DQT_NO_DEBUG -DQT_CORE_LIB -DQT_HAVE_MMX -DQT_HAVE_3DNOW
> -DQT_HAVE_S
> SE -DQT_HAVE_MMXEXT -DQT_HAVE_SSE2 -DQT_THREAD_SUPPORT
> -I"..\..\qt_static_4.7.4\
> include\QtCore" -I"..\..\qt_static_4.7.4\include" -I"dllQDECL"
> -I"..\..\qt_stati
> c_4.7.4\include\ActiveQt" -I"release"
> -I"..\..\qt_static_4.7.4\mkspecs\win32-g++
> " -o release\dllfct.o dllQDECL\dllfct.cpp
> g++ -Wl,-s -shared -Wl,--out-implib,release\libqtdll.a -o release\qtdll.dll
> rele
> ase/dllfct.o  -L"d:\qt_static_4.7.4\lib" -lQtCore -lole32 -luuid -lws2_32
> -ladva

IIRC the correct linker-command for linking a static library needs to be
the absolute path of the .a file. -L/-l are only used by gcc for shared
libs. So it seems that qmake generates the wrong Makefile contents, you
could verify that by copying the line, removing the -L and -lQtCore
arguments and replace that with something like
d:\qt_static_4.7.4\lib\libQtCore.a (provided that this file actually
exists). If that works, you'd have to dive into qmake code or file a
report with the bugtracker to find out (or have someone else find out)
why qmake generates these incorrect linker arguments.

Andreas