Cannot resolve the symbols from a custom dll

[magpielover]

Hello,
I am very close to tear all my hairs out. I have been trying to resolve the functions from my custom dll but so far, no luck.

Here is the template I use:

QLibrary library("E:/QT_works/myDll.dll");
 
if(library.load())
    qDebug()<<"Loading done";
 
 
 typedef void (*MyPrototype)();
 MyPrototype myFunction = (MyPrototype) myLib.resolve("myFunction");
 if (myFunction)
     myFunction();

QLibrary library("E:/QT_works/myDll.dll");

if(library.load())
    qDebug()<<"Loading done";


 typedef void (*MyPrototype)();
 MyPrototype myFunction = (MyPrototype) myLib.resolve("myFunction");
 if (myFunction)
     myFunction();

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Loading is successful. However, symbols cannot be resolved.
I used debugger and after the myLib.resolve step, the following error appears on the window where name and values are shown;

bq. errorString "Cannot resolve symbol "myFunction" in E:/QT_works/myDll.dll: The specified procedure could not be found." QString

I also used

HINSTANCE hDLLFeX;
              hDLLFeX=LoadLibrary(L"myDll.dll");
              if(hDLLFeX)
                  qDebug()<<"LOAD SUCCESSFUL";
 
             MyPrototype myFunction = (MyPrototype)  GetProcAddress(hDLLFeX, "myFunction");

HINSTANCE hDLLFeX;
              hDLLFeX=LoadLibrary(L"myDll.dll");
              if(hDLLFeX)
                  qDebug()<<"LOAD SUCCESSFUL";

             MyPrototype myFunction = (MyPrototype)  GetProcAddress(hDLLFeX, "myFunction");

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Both return a null pointer.
It's obvious that I cannot find the function declared in the library source file, but I guess I used correct syntax when declaring my function. What I used was

extern "C" {
...
void myFunction(int,int)
 
}

extern "C" {
...
void myFunction(int,int)

}

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It's good to mention that the same dll was used by someone else earlier in VS 6.0.

I also downloaded DependencyWalker and check the names of the functions inside myDll.dll. I noticed something which seemed to be interesting. The name of the function which dependencywalker shows is _Z8myFunctionPd, _Z8 in front and Pd at the end of the function. I guess it shouldn't be a problem.
I am not sure if I should resolve the symbols by the name shown in dependencywalker or the original name declared in extern "C".

I am hoping someone might be able to help me.

Thanks

[high_flyer]

did you export the class/function ?

[magpielover]

I am using the below in the common API.h file.
#ifndef FEX_API_H
#define FEX_API_H

#ifdef WIN32
#ifndef DLLEXPORT
#define DLLEXPORT __declspec(dllexport)
#endif
#endif

extern "C" {

...
....
typedef int DLLEXPORT (*MyPrototype )(double*);

}

[high_flyer]

Well,

int MyPrototype(double *);

int MyPrototype(double *);

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is not the same as

void MyPrototype();

void MyPrototype();

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which you are calling.

[magpielover]

Hello,
I used identifiers in Qlibrary template so sorry for the mistake I made. I have found the solution.
I had directly converted the code from VS 6.0 so .def file is used to add the export directive to the object file. However, in the newer versions of compilers such as MinGW and VS 11, __declspec(dllexport) is used to add the export directive automatically. I just added declared the functions with __declspec(dllexport) keyword and problem is solved.
Thank you. I really appreciate the helpful comments.