Compilation Error 3

anand471

I am developing a Qt dll project (SampleCOMDll.dll) with a library project named "samplelibrary" in Qt 5.2.1. using Qt Creator 3.0.1.
On compilation I am getting a errors (Error 3).

How do I fix this? Do I need any other pack to be installed.

Project Details:
I created an empty dll project named "SampleCOMDll" and a then a library project named "samplelibrary" (Template: Library --> C++ Library --> Shared Library)
And I have an created an object for "samplelibrary" in "SampleCOMDll".

On compilation of "SampleCOMDll" project, my application is giving a compile Error 3 without generating the idl file.
But "SampleCOMDll.dll" is getting generated. I am not able to use the .dll in my application. (Error details are listed below).

How do I fix this? Do I need any other pack to be installed?

Also I observed that if I do not craete any object of "samplelibrary" in "SampleCOMDll", there are no compilation errors and idl is generated.

P.S: I am using installation from pack "qt-opensource-windows-x86-mingw48_opengl-5.2.1.exe" and I have Microsoft Visual Studio 2008 installed.

Compile output has the following errors.

bq. C:\Qt\Qt5.2.1\5.2.1\mingw48_32\bin\idc.exe debug\SampleCOMDll.dll /idl debug/SampleCOMDll.idl -version 1.0
debug\SampleCOMDll.idl
Couldn't load library file debug\SampleCOMDll.dll
Class has no metaobject information (error in debug\SampleCOMDll.dll)!
Makefile.Debug:78: recipe for target 'debug\SampleCOMDll.dll' failed
mingw32-make[1]: [debug\SampleCOMDll.dll] Error 3 (ignored)

I am giving my Project Details below:

Project "SampleCOMDll.pro" File:

@TEMPLATE = lib
TARGET = SampleCOMDll

CONFIG += warn_off dll
QT += axcontainer
QT += axserver
QT += widgets
QT += opengl
QT += core
RC_FILE = SampleCOMDll.rc
DEF_FILE = SampleCOMDll.def
HEADERS +=
sampleclass.h
SOURCES +=
sampleclass.cpp

win32: LIBS += -L$$PWD/../Bin/debug/ -lSampleLibrary
INCLUDEPATH += $$PWD/../Bin/debug
DEPENDPATH += $$PWD/../Bin/debug@

Project "samplelibrary" File:

@QT += widgets opengl

TARGET = SampleLibrary
TEMPLATE = lib

DEFINES += SAMPLELIBRARY_LIBRARY

SOURCES += samplelibrary.cpp

HEADERS += samplelibrary.h
samplelibrary_global.h

unix {
target.path = /usr/lib
INSTALLS += target
}@

sierdzio

MinGW and MSVC compilers are not compatible, you should use the same compiler for compiling both projects (I am not sure whether you are doing that or not).

anand471

Thanks for the reply.

I am actually using Qt Creator 3.0.1 to compile both the projects. I hope QT Creator IDE uses MinGW compilers. Am I correct?

sierdzio

Most probably you are. You can check it in your project settings ("Project" panel on the keft hand side of Qt Creator window).

ambershark

I noticed the compile is trying to use a dll. If you are using qt creator and mingw then DLLs would be named as .so files and libs would be .a. So if it is trying to use a DLL inside of a mingw project it won't work, and would indeed say it couldn't find any symbols.

Looks like what sierdzio said is happening and you are mixing 2 different compilers/binaries.