MATLAB interface to C library: defineargument() doesn't define the 'length' argument if already mentioned as part of the pointer argument

Hello,

MATLAB Version: 9.13.0.2049777 (R2022b)

Operating System: Microsoft Windows 10 Enterprise Version 10.0 (Build 19045)

I am trying to call C function (in a shared object) from MATLAB following the documentation in 'MATLAB interface to C library'.

1. I am able to generate the interface dll file successfully. For the function "void mean(float32_t *v, uint32_t len);", I modified the SHAPE parameter for the argument 'v' to 'len' as instructed in the documentation.

defineArgument(meanDefinition, "v", "clib.array.library.Float", "input", "len", "Description", "[in] v Pointer to input array"); % <MLTYPE> can be "clib.array.library.Float", or "single"

defineArgument(meanDefinition, "len", "uint32", "Description", "[in] len Number of elements in array");

After this, I built the interface file and it's successful as well. However, when I call the function from matlab like this, clib.library.mean(buffer, size), it throws an error as incorrect number of arguments. So when I print the summary of the interface file, I notice that the type of second argument 'len' is missing/not defined.

=> clib.library.mean(clib.array.library.Float)

But when I don't specify the SHAPE parameter of 'v' argument as 'len' but just as 1 (for the sake of debugging),

defineArgument(meanDefinition, "v", "clib.array.library.Float", "input", 1, "Description", "[in] v Pointer to input array"); % <MLTYPE> can be "clib.array.library", or "single"

and build it, the summary has the second argument defined.

=> clib.library.mean(clib.array.library.Float,uint32)

2. Also the argument “v” is supposed to be of direction “inputoutput”. Because the list of values it points to are modified by the function. So when I change to it, it throws the following error,

Error using clibgen.FunctionDefinition/defineArgument

Invalid direction specified for argument 'v'. Expected direction is 'input'

Thanks,

Jerome.

[Stefanie Schwarz]

@Jerome Almon Moderator comment: Removed the MATLAB license number from the post.

[Liam]

For point 2. Use lib.Pointer. (https://uk.mathworks.com/help/matlab/matlab_external/working-with-pointers.html). InputOutput would suggest your method returns the pointer which it doesn't.

For point 1. Would also appreciate information.