post  QString::toWCharArray error LNK2019

davinci (5)   Link to this post
Hi!
I'm fairly new to programming in C++ (only done Java before). I try to read data from a *.dat file.
As this file is selcted by the user via a GUI(done with QT) there isn't one special file to test with.

I wrote the following method to read the data - there are 3 times 2 bytes at the beginning of each *.dat file which specify the amount of data given for x, y and z direction
- this is why I only try to read these 2 bytes for the beginning

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void MainWindow::loadFileData(const QString &fileName){
ifstream is;
WCHAR * file;
fileName.toWCharArray(file); 
is.open (file, ios::binary );
	

int length=2;
char * sizeX = new char [length];
char * sizeY = new char [length];
char * sizeZ = new char [length];
	
is.read (sizeX,length);
is.read (sizeY,length);
is.read (sizeZ,length);
}


I did include:
#include <QtGui>
#include <iostream>
#include <fstream>
#include <QString>
#include <string>

#include "mainwindow.h"
#include "glwidgetmain.h"
#include "window.h"
#include "stdio.h"

when trying to build the project I receive the following error:

1>------ Build started: Project: Visualisierung, Configuration: Debug Win32 ------
1>Compiling...
1>mainwindow.cpp
1>c:\vislu\vis_proj\mainwindow.cpp(194) : warning C4700: uninitialized local variable 'file' used
1>Linking...
1>mainwindow.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: int __thiscall QString::toWCharArray(wchar_t *)const " (__imp_?toWCharArray@QString@@QBEHPA_W@Z) referenced in function "private: void __thiscall MainWindow::loadFileData(class QString const &)" (?loadFileData@MainWindow@@AAEXABVQString@@@Z)
1>C:\vislu\vis_proj\Debug\Visualisierung.exe : fatal error LNK1120: 1 unresolved externals
1>Build log was saved at "file://c:\vislu\vis_proj\Debug\BuildLog.htm"
1>Visualisierung - 2 error(s), 1 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========


I guess I missed an include but I can't get rid of this error so far no matter what I try.

Thanks for your help!
Last edited on
guestgulkan (1037)   Link to this post
Have you linked against the appropriate QT library?.
davinci (5)   Link to this post
yes I linked against "$(QTDIR)\lib"; where QTDIR is defined in the windows environment variables as path to the QT folder
all other methods needing QT do work fine - so I guess linking QT is ok
guestgulkan (1037)   Link to this post
It is just that:
1. The QString stuff is in the qtcore library (QT has about 30 libraries)
2. The QString::toWCharArray function did not appear in QT until version 4.2


(And another thing is that you actually have to allocate the WCHAR buffer - which you are not actually doing);
davinci (5)   Link to this post
Thanks for your help so far!

I use QT 4.5.3 - do I have to link each library needed on its own? I do link the whole library folder which holds QtCore4.lib as well. Is this the one meant?

concerning the WCHAR issue I added the following:

int namelength = fileName.length();
WCHAR * file;
file = (WCHAR *) malloc (namelength);
fileName.toWCharArray(file);

to allocate the buffer - I'm not sure wether I did it correctly?
Unfortunately I still receive the same error!
guestgulkan (1037)   Link to this post
You link libraries as required.
QtCore4.lib is the one I'm particularly thinking about (QtCore4d.lib is the debugging version)
How are you using qt - are you using an IDE - if so which one - we should be able to get this thing sorted in no time at all.
davinci (5)   Link to this post
I'm not using an IDE - I downloaded the QT sources, compiled them and installed the addin for msvc
I started using the QT creator but switched to doing the GUI moddeling without creator
guestgulkan (1037)   Link to this post
Ah, that is what I use. I really like it.
Bring up the project properties dialog and go linker ->input
What (libraries) have you got listed in the Additional Dependencies box??
davinci (5)   Link to this post
yeah QT works quite nice - but it's a big change to switch from Java and especially Eclipse to C++ and MSVC

this is what I've got as Additional Dependencies:

opengl32.lib glu32.lib gdi32.lib user32.lib $(QTDIR)\lib\qtmaind.lib $(QTDIR)\lib\QtOpenGLd4.lib $(QTDIR)\lib\QtGuid4.lib $(QTDIR)\lib\QtCored4.lib glew32.lib devil.lib

guestgulkan (1037)   Link to this post
Damn, looks like the appropriate library is being linked.
I will try to duplicate the error tomorrow.
guestgulkan (1037)   Link to this post
I tried the function and it worked for me.

(My QT version is 4.3.3).


(Do a project clean and rebuild and see what happens)

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