Why are the functions from the dll loaded into MATLAB using LOADLIBRARY unavailable?

I am attempting to use LOADLIBRARY from the MATLAB Interface to Shared Libraries (i.e. GenericDLLs) to access a .dll file in MATLAB. It appears that I have successfully loaded the library into MATLAB, except for some warning messages.

The code below demonstrates the loading of my Windows dll:

loadlibrary('FOO.dll','C:/MyD/Libraries/FOO_Prototypes.h','includepath','C:/MyD/Libraries/')

After loading the dll into MATLAB, I receive the following warning messages:

 Warning: The data type 'error' used by function VPX_InsertMessageRequest does not exist

 (Type "warning off MATLAB:loadlibrary:typenotfound" to suppress this warning.)

 Warning: The data type 'error' used by function VPX_InsertMessageRequest does not exist

 (Type "warning off MATLAB:loadlibrary:typenotfound" to suppress this warning.)...

I verified that the dll is loaded into MATLAB by using the LIBISLOADED function:

libisloaded('FOO')

However, when I attempt to view the functions in the DLL with LIBMETHODSVIEW, I receive an error:

libmethodsview('FOO')

 ??? Error using ==> libmethodsview

 No class lib.FOO can be located or no methods for class lib.FOO

Answer 1

[MathWorks Support Team]

The problem of the dll functions not being available within MATLAB can be attributed to a number of things:

1. The improper use of

 __declspec(dllexport)

This should be

 __declspec(dllimport)

Or, you can avoid using the keyword entirely.

2. There is a bug in the LOADLIBRARY tool that causes a failure when multiple variables are declared on a line in a struct definition.

3. Avoid using variables or typedef names that begin with native C data types.