How to set up a C++ function so that it can be used by p/invoke?

Question

Hopefully this is a brainlessly easy question, but it shows my lack of expertise with C++. I\'m a C# programmer, and I\'ve done extensive work with P/Invoke in the past wit

Answer 1

Extending Reed's correct answer.

Another issue you can run into when exposing a C++ function via PInvoke is using invalid types. PInvoke can really only support marshalling of primitive types and plain old data struct / class types.

For example, suppose TestFunc had the following signature

void TestFunc(std::string input);

Even adding extern "C" and __declspec(dllexport) would not be enough to expose the C++ function. Instead you would need to create a helper function which exposed only PInvoke compatible types and then called into the main function. For example

void TestFunc(const std::string& input) { ... }

extern "C" _declspec(dllexport)  void TestFuncWrapper(char* pInput) {
  std::string input(pInput);
  TestFunc(input);
}