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PODLL project on Windows: Unresolved External Symbol
 

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  1. PODLL project on Windows: Unresolved External Symbol
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    <p>I'm creating a DLL project with Visual Studio 2012 with the intent of calling the functions from a Delphi project. I've already turned off C++ name mangling by wrapping my functions in extern "C" { /* ... */ } but to avoid the C name decoration, I'm using a DEF file.</p> <p>Here's a snippet of code describing how I have things laid out:</p> <pre><code>// MyFile.h #ifdef MYPROJECT_EXPORTS #define MYPROJECT_API __declspec(dllexport) #else #define MYPROJECT_API __declspec(dllimport) #endif extern "C" { extern MYPROJECT_API void __stdcall do_something(); } </code></pre> <p>The .cpp file is equivalently structured. Everything matches fine. </p> <p>I added a .def file to my project folder containing the following content:</p> <pre><code>LIBRARY MyProject EXPORTS do_something=_do_something@0 </code></pre> <p>When I build my project, everything works okay. However when I add the linker option</p> <pre><code>/DEFS:MyProject.def </code></pre> <p>I start getting errors regarding unresolved external symbols. Has anybody had this kind of issue before? I'm not new to either C++ or C but this is my first time building a DLL on Windows, as I'm primarily a Unix developer. My hypothesis is that I'm either misunderstanding or misusing the __declspec decorator, as it only breaks when I link in the def file: when I remove that flag from the linker options it builds cleanly, except with C-style decorated symbols.</p> <p>EDIT: Thanks for the comments everyone, but I've gotten myself figured out now. My issue came from the fact that I was using the def file during the linking phase during creation of my DLL. I need to use the def file when using the DLL, not creating it, and everything is peachy.</p>
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    1. COI guess the linker doesn't find `_do_something@0`. Have you tried leaving just `do_something` or `do_something=do_something` in your EXPORTS section (instead of `=_do_something@0`)?
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      1. PODLL project on Windows: Unresolved External Symbol
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    2. COI believe you want to use the .DEF file or the __declspec, but not both.
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      1. PODLL project on Windows: Unresolved External Symbol
      1. USAdrian McCarthy
    3. CONothing obviously wrong. Then again, we can't see the linker errors. Don't make us guess at them.
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      1. PODLL project on Windows: Unresolved External Symbol
      1. USHans Passant
 

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