Search code examples
c++visual-studio-2010dlldllexport

How to generate DLL from existing C++ code using DEF file in Visual Studio 2010

I've inherited a C++ project, and I need to transform it in a DLL, to use it in other projects.

The code is framed in a Visual Studio 2010 solution. I'm able to compile it and generate a DLL file, but there's no associated lib file. I'm not a Windows developer, but seems that I need to export the functions that I want to be used, and there are two ways:

First option would imply to manually add __declspec(ddlexport) in front of every class or function I want to export. As there are a lot of classes, and I don't have the control of all the apps which are going to link against the library, the second option (DEF files) looks more promising.

Is there any way to generate a DEF file from existing DLL file? I've tried different solutions:

  • Using expdef. It just crash with no info at all.

  • Using dumpbin. I don't see functions names. Just this:

    File Type: DLL

    Summary

        1000 .data
    2000 .idata
   18000 .rdata
    5000 .reloc
    1000 .rsrc
   98000 .text
   48000 .textbss

Nothing more. I guess that means I'm not exporting anything. But, that's exactly what I'm trying to do. How do I do it?

Solution

  • After repeatedly coming across this problem for a couple of years I've today found a solution. It's a little hacky, but it actually might be the best possible way with Visual Studio.

    Since you don't want to export EVERY possible symbol (especially since your DLL may include large static libraries itself), and you can't edit the files with symbols you want to have available (for me it's because they're 3rd party libraries which must be statically linked to follow their usage pattern), and DEF is the best solution.

    If we have:

    • Application (EXE)
    • Library (DLL)
    • Library has .DEF file which means that when you build, symbols listed in the .DEF will be exported to the Library .DLL and listed in the .LIB file.
    • .DEF file is empty
    • Application links Library's LIB file

    NOW BUILD!

    OK, we get a lot of linker errors... Linker errors

    Now go to the "Output" tab, and notice that within the text of the output is the symbol names at the end of each linker error line:

    Linker error text

    We can create a little script with takes the last 'word' of every line, takes off the brackets, and then put that in your DEF file. And it works!

    Like I said it's a little hacky (since you only end up with the symbols used by the Application at that time). But actually since you don't want to export everything, and you might need symbols in the libraries which that library statically links, it's probably the most accurate way of going about this.

    (NB : In my case it's mostly a problem with trying to get the plugin DLL have access to symbols in the application EXE)