Unable to find an entry point when loading an unmanaged DLL

[Jordan C Atlas]

Hello, I have an unmanaged C++ dll that I would like to load in a managed C++ application. I can call methods in the dll from an *unmanaged* program with no issues. I set up the import using: // Set up the import [DllImportAttribute("lib.dll")] int function(); The project is correctly set to find the libary files. When I run the compiled program, it throws an execption at the line: function(); The exception is: An unhandled exception of type 'System.EntryPointNotFoundException' occurred in testManaged.exe Additional information: Unable to find an entry point named function in DLL lib.dll. This error indicates that it cannot find the function in my libarary, but I know the function is there and accessible because I can access it from unmanged code. Is there something wrong with my import statement? Anything else? Thanks, --Jordan -- modified at 23:40 Thursday 19th January, 2006

[Stephen Hewitt]

Try adding a ExactSpelling=true. I think the syntax would be like this: [DllImportAttribute("lib.dll", ExactSpelling=true)] int function(); But I'm not a dotNET guru... Steve

[Jordan C Atlas]

The ExactSpelling attribute did not fix it (I get the same exception), but thank you for the suggestion. --Jordan

[Stephen Hewitt]

Can you post the declaration of the unmanaged function (so I can check the calling convention) - The C++ code. Steve -- modified at 0:06 Friday 20th January, 2006 FIXED errors

[Jordan C Atlas]

I found the problem -- I was using an improper function prototype for the shared function. I reset the import to say: // Set up the import [DllImportAttribute("lib.dll")] extern "C" int function(); I'm not sure why the extern "C" is necessary, so here is a link to the article that tipped me off: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconcreatingprototypesinmanagedcode.asp[^] Thanks again to Stephen for his suggestion. --Jordan

[Jordan C Atlas]

Stephen, The function was declared as: LIB_API int function(void); where I have #define LIB_API __declspec(dllexport) Changing it to: extern "C" LIB_API int function(void); seems to have fixed the problem -- I'd be happy to hear an explanation for that if you have one. Thanks, --Jordan -- modified at 0:14 Friday 20th January, 2006