[SOLVED] Issue when using class created with my Dll

[BlackMamba]

Hello,
I created a C++ Dll Obo which compiles fine.

• #include "obo_global.h"
• class OBOSHARED_EXPORT Obo
  {
  public:
  Obo();
  std::vector<EI*> generate();
  };

where EI is a class defined in another part of code.
Now I want to test this Obo library in a separate code OboTester but don't know why but I can't use this EI class as I have a unresolved external symbol, even whith the "EI.h" included in OboTester.
Here is the code :

• int main(int argc, char argv[])
  {
  QCoreApplication a(argc, argv);
  Obo myObo;
  std::vector<EI> res = myObo.generate();
  // until here it works fine
  EI myEI; // crashes at compile time
  return a.exec();
  }

What did I do wrong here?
Thanks

[mcosta]

Hi,

I don't know if is a type but in header file generate returns a std::vector<El*> and in main you assign it to a std::vector<El>.

BTW, before access to element [0] you should check the vector is not empty.

Can you post the compile/link error?

[BlackMamba]

Hi,
Sorry I edited with something more concrete, its not a problem of empty vector, it doesn't compile when I want to instantiate the class EI.
The error :
main.obj:-1: erreur : LNK2019: unresolved external symbol "public: __cdecl EI::EI(void)" (??0EI@@QEAA@XZ) referenced in function main

[mcosta]

How is defined El ??

Seems El doesn't have a default constructor

[BlackMamba]

@mcosta
Well, its defined in the Obo project library as a standard class.
It has a default constructor :
EI::EI()
{

}

[mcosta]

Can you post the code and the qmake project file??

[BlackMamba]

Well, which code? Obo is around 40k lines of code :/
Which qMake file? The one from the library?

Can this be related to EXporting DLL classes? I am not familiar with that at all :(

[mcosta]

@BlackMamba said:

OBOSHARED_EXPORT

Do you used this also for El?
The library .pro file should be enough.

Seems the the El constructor in not available outside the library.

[BlackMamba]

I didn't use this for the EI class, let me try that !

[BlackMamba]

Now it compiles but crashes immediately when I execute the code.
Here is the pro file :

• include(Obo.pri)
  QT -= gui
  TARGET = Obo
  TEMPLATE = lib
  DEFINES += Obo_LIBRARY
  SOURCES += Obo.cpp
  HEADERS += Obo.h
  Obo_global.h
  unix {
  target.path = /usr/lib
  INSTALLS += target
  }

and the .pri file :

• SOURCES +=
  ...
  $$PWD/src/OboInterface/EI.cpp
  HEADERS +=
  $$PWD/src/OboInterface/EI.h
  ...
  DEPENDPATH += $$PWD/src/OboInterface
  INCLUDEPATH+= $$PWD/src/OboInterface

[mcosta]

Ok,

where's the crash? which line? Are you able to collect a crash dump?

[BlackMamba]

It crashes at the same line, when I try to instantiate the object :
EI myEI;

[mcosta]

How is defined El??

Try to provide as much information as possible; otherwise we'll be not able to help you

[BlackMamba]

With an empty class, I have the same issue :

• #ifndef EI_H
  #define EI_H

class EI
{
public:
EI();
~EI();
};

#endif // EI_H

main.obj:-1: erreur : LNK2019: unresolved external symbol "public: __cdecl EI::EI(void)" (??0EI@@QEAA@XZ) referenced in function main

With this :

#ifndef EI_H
#define EI_H

#include "obo_global.h"

class OBOSHARED_EXPORT EI
{
public:
EI();
~EI();
};

#endif // EI_H

same error :(

[mcosta]

I mean the implementation of El.

Can you post the crash dump?

[BlackMamba]

After some clean, good news, I have a new mistake when I add OB0SHARED_EXPORT for the EI class:
main.obj:-1: erreur : LNK2019: unresolved external symbol "__declspec(dllimport) public: __cdecl EI::EI(void)" (_imp??0EI@@QEAA@XZ) referenced in function main

[BlackMamba]

@mcosta I gave youi the implementation, I deleted all the methods, its an empty class with ctor and dtor only.

[mcosta]

Sorry, if you don't show the code I can't help you!

[BlackMamba]

@mcosta Please read my last answer ;)

[mcosta]

So, now you have the link error or still the crash??

You said before you was able to compile and link but you get a crash and now again the link error. It's a little bit confusing

[BlackMamba]

Now the crash ... Yes, its confusing for me too.
Thats looks so simple, I don't understand what I am doing wrong.
The crash means he cant find the EI cpp implementation at runtime.

[BlackMamba]

OMG!!!!! I am soooooo stupid ... I didn't update the copy of the Obo.dll .....
Sorry for your time mcosta !

You gave me the right answer by adding OB0SHARED_EXPORT for the classes you need to use after ...
Thanks !

[mcosta]

Ok, no problem!

Happy programming