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Undefined refence to '_imp__FunctionName'

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  • SGaistS Offline
    SGaistS Offline
    SGaist
    Lifetime Qt Champion
    wrote on last edited by
    #2

    Hi,

    Where the symbols of that method properly exported ?
    Is that compiler compatible with the one you are using currently ? You can't mix and match libraries from different compilers. For example MinGW and VS cannot be mixed.
    Is the library of the same architecture as your main application ?

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    Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

    M 2 Replies Last reply
    0
    • SGaistS SGaist

      Hi,

      Where the symbols of that method properly exported ?
      Is that compiler compatible with the one you are using currently ? You can't mix and match libraries from different compilers. For example MinGW and VS cannot be mixed.
      Is the library of the same architecture as your main application ?

      M Offline
      M Offline
      MNag
      wrote on last edited by
      #3

      @SGaist

      Hi, Thanks for reply!!

      I am new to C++ builder not sure about the compiler compatible need to check on that.

      this is how i am exporting the function in dll source code using Emberacadero C++ builder.

      extern "C" __declspec(dllexport) void myfun ( int * a);

      1 Reply Last reply
      0
      • SGaistS SGaist

        Hi,

        Where the symbols of that method properly exported ?
        Is that compiler compatible with the one you are using currently ? You can't mix and match libraries from different compilers. For example MinGW and VS cannot be mixed.
        Is the library of the same architecture as your main application ?

        M Offline
        M Offline
        MNag
        wrote on last edited by
        #4

        @SGaist

        BCC32C this is the compiler name which is used in Embarcadero C++ builder

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        • SGaistS Offline
          SGaistS Offline
          SGaist
          Lifetime Qt Champion
          wrote on last edited by
          #5

          You seem to be doing some pretty convoluted things here.

          Your method seems to be a pure C method that you try to wrap in a C++ library so you should rather build a C dll that does not have the same constraints as a C++ dll. As for your use of the __declspec instruction, it's wrong. You have to export the symbol on build and then import the symbol when linking to the library.

          For building C++ shared library, the dedicated chapter in Qt's documentation explains it pretty well.

          Interested in AI ? www.idiap.ch
          Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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          • SGaistS SGaist

            You seem to be doing some pretty convoluted things here.

            Your method seems to be a pure C method that you try to wrap in a C++ library so you should rather build a C dll that does not have the same constraints as a C++ dll. As for your use of the __declspec instruction, it's wrong. You have to export the symbol on build and then import the symbol when linking to the library.

            For building C++ shared library, the dedicated chapter in Qt's documentation explains it pretty well.

            M Offline
            M Offline
            MNag
            wrote on last edited by MNag
            #6

            @SGaist

            i tried as below aswell but still have same issue

            #ifdef IN_DLL
            #define EXPORT_IMPORT __export
            #else
            #define EXPORT_IMPORT Q_DECL_IMPORT //__import
            #endif

            #ifdef BORLANDC
            extern "C" void __stdcall EXPORT_IMPORT myfun( int * a);
            #else
            extern "C" void __stdcall EXPORT_IMPORT myfun( int * a);
            #endif

            Earlier i was using:

            i was exporting on C++ builder side and importing in QT using following

            QT:
            extern "C" __declspec(dllimport) void myfun( int * a);

            C++ Builder:
            extern "C" __declspec(dllexport) void myfun( int * a);

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            • SGaistS Offline
              SGaistS Offline
              SGaist
              Lifetime Qt Champion
              wrote on last edited by
              #7

              Again: why are you trying to make a C++ library if you have only C functions ? It really complicate things for nothing.

              Interested in AI ? www.idiap.ch
              Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

              M 1 Reply Last reply
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              • SGaistS SGaist

                Again: why are you trying to make a C++ library if you have only C functions ? It really complicate things for nothing.

                M Offline
                M Offline
                MNag
                wrote on last edited by
                #8

                @SGaist

                Actually i want to migrate old dll project (big project) to C++ Builder in that they are using above mentioned method soi thought it will be convenient to do the same.

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                • SGaistS Offline
                  SGaistS Offline
                  SGaist
                  Lifetime Qt Champion
                  wrote on last edited by
                  #9

                  That starts to make things a bit clearer.

                  On a side note, you used the Qt macros wrongly.

                  So your original dll is a C dll that you would like to port to C++ and you are using the technique you saw from the use of the library by the Borland compiler ?

                  Interested in AI ? www.idiap.ch
                  Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                  • SGaistS SGaist

                    That starts to make things a bit clearer.

                    On a side note, you used the Qt macros wrongly.

                    So your original dll is a C dll that you would like to port to C++ and you are using the technique you saw from the use of the library by the Borland compiler ?

                    M Offline
                    M Offline
                    MNag
                    wrote on last edited by
                    #10

                    @SGaist

                    Yes, that's Correct.

                    What's wrong with Qt macros?

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                    • SGaistS Offline
                      SGaistS Offline
                      SGaist
                      Lifetime Qt Champion
                      wrote on last edited by
                      #11

                      You did not use Q_DECL_EXPORT.

                      Interested in AI ? www.idiap.ch
                      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                      • SGaistS SGaist

                        You did not use Q_DECL_EXPORT.

                        M Offline
                        M Offline
                        MNag
                        wrote on last edited by
                        #12

                        @SGaist said in Undefined refence to '_imp__FunctionName':

                        Q_DECL_EXPORT.

                        Thought of using the C++ builder macro for exporting since i am exporting in C++ builder and importing in Qt so i used Qt macro for importing.

                        1 Reply Last reply
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