Qt5 - Link pHash library “undefined reference”

Question

I would like to add an external library called pHash . I added this to .pro file :

win32:CONFIG(release, debug|release): LIBS += -L$PWD/Libs/pHash-0.9.4/release -lpHash
else:win32:CONFIG(debug, debug|release): LIBS += -L$PWD/Libs/pHash-0.9.4/debug -lpHash

INCLUDEPATH += $PWD/Libs/pHash-0.9.4
DEPENDPATH += $PWD/Libs/pHash-0.9.4

win32:CONFIG(release, debug|release): PRE_TARGETDEPS += $PWD/Libs/pHash-0.9.4/release/pHash.lib
else:win32:CONFIG(debug, debug|release): PRE_TARGETDEPS += $PWD/Libs/pHash-0.9.4/debug/pHash.lib

But no one function of the library is working. When I try to use one, I have build error "undefined reference to pHashFunction". There is an example of use :

#include "myclass.h"

#define HAVE_IMAGE_HASH 1 // config
#include "pHash.h"

void MyClass::perform() {
    const char *msg = ph_about();
    qDebug() << msg;
}

Then there is the build log :

C:/Qt/Tools/mingw492_32/bin/mingw32-make -f Makefile.Debug clean
mingw32-make[1]: Entering directory 'C:/Users/vi/Documents/Programmation/QtWorkspace/build-myProject-Desktop_Qt_5_5_0_MinGW_32bit-Debug'
rm -f debug/qrc_qml.cpp
rm -f debug/moc_myclass.cpp
rm -f debug/main.o debug/myclass.o debug/qrc_qml.o debug/moc_myclass.o
mingw32-make[1]: Leaving directory 'C:/Users/vi/Documents/Programmation/QtWorkspace/build-myProject-Desktop_Qt_5_5_0_MinGW_32bit-Debug'
C:/Qt/Tools/mingw492_32/bin/mingw32-make -f Makefile.Release clean
mingw32-make[1]: Entering directory 'C:/Users/vi/Documents/Programmation/QtWorkspace/build-myProject-Desktop_Qt_5_5_0_MinGW_32bit-Debug'
rm -f release/qrc_qml.cpp
rm -f release/moc_myclass.cpp
rm -f release/main.o release/myclass.o release/qrc_qml.o release/moc_myclass.o
mingw32-make[1]: Leaving directory 'C:/Users/vi/Documents/Programmation/QtWorkspace/build-myProject-Desktop_Qt_5_5_0_MinGW_32bit-Debug'
01:31:34: Le processus "C:\Qt\Tools\mingw492_32\bin\mingw32-make.exe" s'est terminé normalement.
01:31:34: Configuration inchangée, étape qmake sautée.
01:31:34: Débute : "C:\Qt\Tools\mingw492_32\bin\mingw32-make.exe" 
C:/Qt/Tools/mingw492_32/bin/mingw32-make -f Makefile.Debug
mingw32-make[1]: Entering directory 'C:/Users/vi/Documents/Programmation/QtWorkspace/build-myProject-Desktop_Qt_5_5_0_MinGW_32bit-Debug'
g++ -c -pipe -fno-keep-inline-dllexport -g -frtti -Wall -Wextra -fexceptions -mthreads -DUNICODE -DQT_QML_DEBUG -DQT_DECLARATIVE_DEBUG -DQT_QUICK_LIB -DQT_GUI_LIB -DQT_QML_LIB -DQT_NETWORK_LIB -DQT_CORE_LIB -DQT_NEEDS_QMAIN -I../myProject -I. -I../myProject/Libs/pHash-0.9.4 -IC:/Qt/5.5/mingw492_32/include -IC:/Qt/5.5/mingw492_32/include/QtQuick -IC:/Qt/5.5/mingw492_32/include/QtGui -IC:/Qt/5.5/mingw492_32/include/QtANGLE -IC:/Qt/5.5/mingw492_32/include/QtQml -IC:/Qt/5.5/mingw492_32/include/QtNetwork -IC:/Qt/5.5/mingw492_32/include/QtCore -Idebug -IC:/Qt/5.5/mingw492_32/mkspecs/win32-g++  -o debug/main.o ../myProject/main.cpp
g++ -c -pipe -fno-keep-inline-dllexport -g -frtti -Wall -Wextra -fexceptions -mthreads -DUNICODE -DQT_QML_DEBUG -DQT_DECLARATIVE_DEBUG -DQT_QUICK_LIB -DQT_GUI_LIB -DQT_QML_LIB -DQT_NETWORK_LIB -DQT_CORE_LIB -DQT_NEEDS_QMAIN -I../myProject -I. -I../myProject/Libs/pHash-0.9.4 -IC:/Qt/5.5/mingw492_32/include -IC:/Qt/5.5/mingw492_32/include/QtQuick -IC:/Qt/5.5/mingw492_32/include/QtGui -IC:/Qt/5.5/mingw492_32/include/QtANGLE -IC:/Qt/5.5/mingw492_32/include/QtQml -IC:/Qt/5.5/mingw492_32/include/QtNetwork -IC:/Qt/5.5/mingw492_32/include/QtCore -Idebug -IC:/Qt/5.5/mingw492_32/mkspecs/win32-g++  -o debug/myclass.o ../myProject/myclass.cpp
In file included from ../myProject/myclass.cpp:3:0:
../myProject/Libs/pHash-0.9.4/pHash.h:299:21: warning: 'cimg_library::CImg<float>* ph_dct_matrix(int)' declared 'static' but never defined [-Wunused-function]
 static CImg<float>* ph_dct_matrix(const int N);
                     ^
'C:\Qt\5.5\mingw492_32\bin\rcc.exe' -name qml ../myProject/qml.qrc -o debug/qrc_qml.cpp
g++ -c -pipe -fno-keep-inline-dllexport -g -frtti -Wall -Wextra -fexceptions -mthreads -DUNICODE -DQT_QML_DEBUG -DQT_DECLARATIVE_DEBUG -DQT_QUICK_LIB -DQT_GUI_LIB -DQT_QML_LIB -DQT_NETWORK_LIB -DQT_CORE_LIB -DQT_NEEDS_QMAIN -I../myProject -I. -I../myProject/Libs/pHash-0.9.4 -IC:/Qt/5.5/mingw492_32/include -IC:/Qt/5.5/mingw492_32/include/QtQuick -IC:/Qt/5.5/mingw492_32/include/QtGui -IC:/Qt/5.5/mingw492_32/include/QtANGLE -IC:/Qt/5.5/mingw492_32/include/QtQml -IC:/Qt/5.5/mingw492_32/include/QtNetwork -IC:/Qt/5.5/mingw492_32/include/QtCore -Idebug -IC:/Qt/5.5/mingw492_32/mkspecs/win32-g++  -o debug/qrc_qml.o debug/qrc_qml.cpp
'C:\Qt\5.5\mingw492_32\bin\moc.exe' -DUNICODE -DQT_QML_DEBUG -DQT_DECLARATIVE_DEBUG -DQT_QUICK_LIB -DQT_GUI_LIB -DQT_QML_LIB -DQT_NETWORK_LIB -DQT_CORE_LIB -DQT_NEEDS_QMAIN -D__GNUC__ -DWIN32 -IC:/Qt/5.5/mingw492_32/mkspecs/win32-g++ -IC:/Users/vi/Documents/Programmation/QtWorkspace/myProject -IC:/Users/vi/Documents/Programmation/QtWorkspace/myProject/Libs/pHash-0.9.4 -IC:/Qt/5.5/mingw492_32/include -IC:/Qt/5.5/mingw492_32/include/QtQuick -IC:/Qt/5.5/mingw492_32/include/QtGui -IC:/Qt/5.5/mingw492_32/include/QtANGLE -IC:/Qt/5.5/mingw492_32/include/QtQml -IC:/Qt/5.5/mingw492_32/include/QtNetwork -IC:/Qt/5.5/mingw492_32/include/QtCore -I. ../myProject/myclass.h -o debug/moc_myclass.cpp
g++ -c -pipe -fno-keep-inline-dllexport -g -frtti -Wall -Wextra -fexceptions -mthreads -DUNICODE -DQT_QML_DEBUG -DQT_DECLARATIVE_DEBUG -DQT_QUICK_LIB -DQT_GUI_LIB -DQT_QML_LIB -DQT_NETWORK_LIB -DQT_CORE_LIB -DQT_NEEDS_QMAIN -I../myProject -I. -I../myProject/Libs/pHash-0.9.4 -IC:/Qt/5.5/mingw492_32/include -IC:/Qt/5.5/mingw492_32/include/QtQuick -IC:/Qt/5.5/mingw492_32/include/QtGui -IC:/Qt/5.5/mingw492_32/include/QtANGLE -IC:/Qt/5.5/mingw492_32/include/QtQml -IC:/Qt/5.5/mingw492_32/include/QtNetwork -IC:/Qt/5.5/mingw492_32/include/QtCore -Idebug -IC:/Qt/5.5/mingw492_32/mkspecs/win32-g++  -o debug/moc_myclass.o debug/moc_myclass.cpp
g++ -Wl,-subsystem,windows -mthreads -o debug/myProject.exe debug/main.o debug/myclass.o debug/qrc_qml.o debug/moc_myclass.o  -lmingw32 -LC:/Qt/5.5/mingw492_32/lib -lqtmaind -lshell32 -LC:/Users/vi/Documents/Programmation/QtWorkspace/myProject/Libs/pHash-0.9.4/debug -lpHash -lQt5Quickd -lQt5Guid -lQt5Qmld -lQt5Networkd -lQt5Cored 
debug/myclass.o: In function `ZN6myclass7performEv':
C:\Users\vi\Documents\Programmation\QtWorkspace\build-myProject-Desktop_Qt_5_5_0_MinGW_32bit-Debug/../myProject/myclass.cpp:11: undefined reference to `ph_about'
collect2.exe: error: ld returned 1 exit status
Makefile.Debug:83: recipe for target 'debug/myProject.exe' failed
mingw32-make[1]: *** [debug/myProject.exe] Error 1
mingw32-make[1]: Leaving directory 'C:/Users/vi/Documents/Programmation/QtWorkspace/build-myProject-Desktop_Qt_5_5_0_MinGW_32bit-Debug'
makefile:34: recipe for target 'debug' failed
mingw32-make: *** [debug] Error 2

Thank you in advance for your help :)

Answer 1

尝试将.c和.cpp添加到您的项目中（dirent.c，ph_fft.c，pHash.cpp，phcomplex.c），但我认为问题在于.dll和.lib不在与您的Qt版本兼容，因为它是使用Visual Studio编译的。

Answer 2

The library pHash is no longer supported and there are many problems.

1. The compiler MinGW 4.9.2 used by Qt is not compatible with .dll files built in MSVC.

2. It is not enough to use the trick "MSVC and MinGW DLLs" , since the function ph_about() is not exported from pHash.dll , for example Building the pHash library on Windows

3. It is possible to integrate all pHash files into Qt project, so the library can be built together with the application. Since the library project is prepared for Visual Studio I would say that the Qt should also be based on VC. However, the library pHash is old. It was written for Visual Studio 2008. Now it gives error on deprecated Windows function SHGetSpecialFolderPathA .

4. It is still prossible to compile everything using Qt MinGW 4.9.2 compiler. In that case it is needed to add DEFINES += HAVE_IMAGE_HASH=1 to the project .pro file to enable that macro also for pHash compilation. However, to use native support for images the libraries libjpeg and libpng also should be compiled with the same compiler, for example Compiling libjpeg If the image libraries are not used, Cimg tries to run some external executable gm.exe (probably from GraphicsMagick).

If the library is needed for some quick task it is possible to consider virtual Linux, since here it can be used out of the box https://stackoverflow.com/a/33002746/4023446