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c#pinvokedllimportdllexport
Tom Davies
Tom Davies

Reputation: 2446

PInvokeStackImbalance when calling a dll function from C#

I'm writing a WPF app that needs to call some C++ code that exists in a dll I've written. I'm always getting PInvokeStackImbalance errors, even with the the most rudimentary test functions. Eg, in the C++ dll:

extern "C" __declspec(dllexport) void Test( int foo);

The function does nothing. The c# side looks like this:

    [DllImport("myDll.dll", CharSet = CharSet.Auto)]
    private static extern void Test( int foo);

And I call this c# function like so:

Test(1)

... and I get a PInvokeStackImbalance!! How can this be?

Thanks in advance...

Tom

Upvotes: 2

Views: 556

Answers (2)

Hans Passant
Hans Passant

Reputation: 942207

Your [DllImport] declaration is missing the CallingConvention. Required, your Test function is Cdecl since you didn't use the __stdcall keyword. The difference between __cdecl and __stdcall is the way the stack gets cleaned up after the call. __cdecl is the default for most C++ compilers, including Microsoft's. To fix it on the C++ side, you'd declare it like this:

extern "C" __declspec(dllexport) 
void __stdcall Test( int foo);

Upvotes: 3

Felice Pollano
Felice Pollano

Reputation: 33272

Try to specify CallingConvention.Cdecl. There is an example in the doc. The default calling convention is Winapi on desktop windows; but your function is declared as extern C.

Upvotes: 4

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