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POUnmanaged struct as return value to managed
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  1. POUnmanaged struct as return value to managed
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    copied!<p>I have a unmanaged third party library (C). I'm trying to write a wrapper in C++/CLI, so I can use the library from C#. I have several C examples, but I can't figure out how to bridge the unmanaged and managed heaps.</p> <p>One of the functions in the library returns a struct, which I need to keep in my managed wrapper. This struct is then used as a parameter for other functions.</p> <p>Working C-example:</p> <p>library.h</p> <pre><code>typedef struct FOO_BAR_STRUCT* FOO_BAR; DLLEXPORT FOO_BAR FooBarCreate(); </code></pre> <p>Example.c</p> <pre><code>#include &lt;library.h&gt; int main(int argc, char* argv[]) { char* address = "127.0.0.1"; FOO_BAR fb = NULL; fb = FooBarCreate(); FooBarRegister(fb, address); } </code></pre> <p>So in my Wrapper, I try to recreate what the example do. I've figured out that the problem is which heap the struct is on, but I haven't been able to figure out how to solve this.</p> <p>My C++ code, compiled as a C++/CLI .dll for use in my C# project.</p> <p>FooBarComm.h</p> <pre><code>#include &lt;library.h&gt; ref class FooBarComm { public: FooBarComm(char* address); ~FooBarComm(); private: FOO_BAR fb; }; </code></pre> <p>FooBarComm.cpp</p> <pre><code>#include "FooBarComm.h" FooBarComm::FooBarComm(char* address) { fb = FooBarCreate(); FooBarRegister(fb, address); } FooBarComm::~FooBarComm() { } </code></pre> <p>And this fails. How can I get the instance of the FOO_BAR struct from the unmanaged code into the managed class, then use it as a argument in later functions.</p> <p>Edit:</p> <blockquote> <p>I fails with a warning LNK4248: unresolved typeref token (0100000D)<br /> error LNK2028: unresolved token (0A00000A) "extern "C" struct FOO_BAR_STRUCT<br /> error LNK2019: unresolved external symbol "extern "C" struct FOO_BAR_STRUCT</p> </blockquote> <p>I guess the problem is that I don't have a definition of the FOO_BAR_STRUCT in any header files that came with the library. I'm starting to dislike this library.</p> <p>Is it sensible to create a unmanaged class that holds the reference to the struct, and then reference this unmanaged class from a managed class?</p> <p>If I change to a "normal" C++ class, I get a different compile error:</p> <p>FooBarComm.h</p> <pre><code>#include &lt;library.h&gt; #pragma unmanaged class FooBarComm { ... </code></pre> <p>I get the compile error:</p> <blockquote> <p>error LNK2019: unresolved external symbol _FooBarCreate referenced</p> </blockquote> <p>Edit 2: </p> <p>Ofcourse it was a missing link to the .lib file.</p>
 

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