Pass a struct from Unity to C++ library

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Hello,

I'm using a C++ custom library I built for Unity in one of my projects. I'm sending a C# struct while invoking a method in the C++ library. These structs are using the exact same names and order in its members on both C++ and C# classes. But only some of the struct members are being received correctly on the C++ side. Others are going back to default value. I only have int and bool members in the struct. No arrays. Any idea what might be happening?

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Answer by Bunny83 · May 24 at 10:04 PM

Like Captain P. said, you should share your code. Keep in mind to use export "C" on the C++ side to avoid name mangling.

On the managed C# side you have to use [StructLayout(LayoutKind.Sequential)] on your struct to ensure a sequential memory layout.

Finally keep in mind that depending on the compiler and platform, in C++ the actual size of an int, long, etc can vary. So again, it would be way easier to provide a clear answer if we had your actual code as reference. If you want to provide the code, feel free to edit your question and add the relevant code snippets.

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SRJMerge · May 25 at 12:02 PM 0

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@Bunny83 Thank you for the response. I indeed needed to add the [StructLayout(LayoutKind.Sequential)] attribute to the struct. I also ended up having to use [MarshalAs(UnmanagedType.U1)] for all the bools and [MarshalAs(UnmanagedType.R4)] for floats inside the struct. This resolved my issue.

Pass a struct from Unity to C++ library

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