Is a .def File Required To Export Functions From DLL?...

Is a .def File Required To Export Functions From DLL?...

• ASharif

  No a DEF file ist not needed. using declspec export is enough.
  To see the exports of a DLL just load the DLL in the dependencies viewer (DEPENDS.EXE).
  If using declspec export and the function belongs to a C++ namespace you have to take care about the name mangeling. May be you have to use extern "C".
  
  

• Aspera

  Yes you can! As you can use any of the system DLLs you can use custom written C++ DLL's too.
  
  The problem with declspec(export) is that the function name still has a leading '_'!
  Using the def file you can define your name without a _!

  
  
  

• deadeye

  Is that means that, we can use C++ _declspec(export) functions from a .NET C# application
  
  When i tried to use that, I received the following error:
  
  Unable to find an entry point named fnSampleDLL in DLL E:\DotNet\Test\SampleDLL\
  Debug\SampleDLL.dll.
  
  I was able to call this function, after defining a module definition file (.def).
  
  Please help me,
  
  Thanks in Advance.
  
  
  

• Will McAfee

  Thanks for the info Martin.  It is appreciated.
  
  

• EddieR

  I created a VS.NET 2003 VC++ Win32 DLL project with the Export Symbols option checked. The Wizard generated a sample .cpp / .h with a __declspec(dllexport) class and function.
  
  In your previous reply, you told that dlls can be used in a C# application even functions are not explicitly exported using module definition (.def) file. I tried calling the created dll from C# console application with the DllImport attribute, It failed throwing the above error (see my previous reply).
  
  But i was able to call the function when i defined that function name in the .def file. Which makes it true that If we can't to use function in the dll which has been exported using __declspec(dllexport) and not exported in the .def file.
  
  So if we want to call a c++ dll function from a c# code, that function needs to be specified with __declspec(dllexport) and also need to mentioned in the .def file.
  
  Code:
  
  file.cpp
  
  //...
  
  __declspec(dllexport) int fnSampleDLL(void)
  {
     return 42;
  }
  
  //...
  
  Please confirm my understanding. Thanks for your reply.
  
  Thanks in Advance.

  
  
  
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