Debug Assertion Failed when calling dll function

[Jordan C Atlas]

Hello, I am using managed code to call a function in an unmanaged DLL. When I call the function, the program runs until the end of the function, and then gives a "Debug Assertion Failed!" dialog box for "Expression: _CrtIsValidHeapPoint(pUserData)". The error occurs no matter what code I have inside the function. For example, removing all the code in the dll function, so that it's just an empty function, does not prevent the error. The only thing that I've done to prevent the error is to comment out the line that calls the dll function. This is how I import the function: // Set up the import [DllImportAttribute("lib.dll")] extern "C" int func(string inputFileName); This is the function declaration in the DLL code: __declspec(dllexport) int func(string inputFileName) Does anyone have any suggestions for how to track this down? Thanks, --Jordan -- modified at 13:10 Friday 20th January, 2006

[Chris Losinger]

what does the DLL's exported function look like ? Cleek | Image Toolkits | Thumbnail maker

[Jordan C Atlas]

Even if I remove the whole function body, I get the same error. So, right now it looks like this: __declspec(dllexport) int func(string inputFileName) { } -- modified at 13:10 Friday 20th January, 2006

[Chris Losinger]

so, you're exporting a function that takes a std::string as input ? i suspect then that the std string ctor is going to be called even if there isn't any code in the body of the function. that could be related to the problem. what if you change that to:

__declspec(dllexport) int func(const char *inputFileName)
{
}

? Cleek | Image Toolkits | Thumbnail maker -- modified at 13:15 Friday 20th January, 2006

[Jordan C Atlas]

Yes! That fixed it. Thanks. So it's not allowed to create a managed function that uses an unmanaged class as input? --Jordan

[Chris Losinger]

Jordan C. Atlas wrote:

So it's not allowed to create a managed function that uses an unmanaged class as input?

i wish i could answer that... but i really don't know. :) glad my suggestion helped, though. Cleek | Image Toolkits | Thumbnail maker