Qt dll loading failed

CBenussi

Hello, I have Qt 5.7 for MinGw 32-bit installed on my Windows 7 64-bit OS. I am trying to load programmatically a dll with the following code:

#include "mainwindow.h"
#include "QLibrary"
#include "QDebug"
#include "QString"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QLibrary myLib("ucrtbased.dll");
    myLib.load();

    if(!myLib.isLoaded()){
        qDebug() <<  myLib.errorString() ;
    } else {
        qDebug() << "All ok";
    }
    return a.exec();
}

and it works with some dll, like ucrtbased.dll, which under the "file" command (in terminal) appears as:

ucrtbased.dll: PE32 executable (DLL) (Console) Intel 80386, for MS Windows

while if I try to load the dll I want to use, which has the following format:

mylib.dll: PE32 executable (DLL) (GUI) Intel 80386, for MS Windows

I get the following error from qDebug():

"Cannot load library mylib.dll: Could not find the specified module."

Both the libraries are in the same directory, so I believe is a format problem. Anyway, the only difference between the two is the (GUI) instead of (console) attribute, but I don't know what it means and how it could affect the loading of the library.

Any suggestion? Thanks in advance.

mrjj

Hi
Is it possible mylib.dll have dependencies on some Qt*.DLLS ?
So when you try to load it, it fails to load those libraries.?

You can use
http://www.dependencywalker.com/
to see if that is the case.

I assume you :
1: compiled the mylib.dll with mingw compiler
2: have mylib.dll near the exe or it can be found via path so that
" Could not find the specified module." do not mean , cannot find mylib.dll

kshegunov

In addition to what @mrjj said, be sure to check if there is such a file at all:

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    if (!QFileInfo("ucrtbased.dll").exists())
        qDebug() << "No such file";
 
    // ...
}

CBenussi

I have found the problem, a silly one actually, so sorry for having you wasting time. The executable file built by Qt resides in another folder from where I was putting the dll (which I did put in the folder of the project/source files), so my program was actually not finding the dll, but ucrtbased.dll had a copy in the library_path so it was loaded anyway. I moved mydll in the exe folder and it works.

Thanks for the support.