LibraryImportAttribute emits DllImport in generated code

[PhilPJL]

I've been experimenting changing some p-invoke DllImport statements to use LibraryImport. For example a simple one:

    [DllImport(Constants.DLLFileName, EntryPoint = "H5Pclose",
        CallingConvention = CallingConvention.Cdecl),
    SuppressUnmanagedCodeSecurity, SecuritySafeCritical]
    public static extern herr_t close(hid_t plist);

changes to (I know these SuppressUnmanagedCodeSecurity, SecuritySafeCritical are null-ops in .NET core)

    [LibraryImport(Constants.DLLFileName, EntryPoint = "H5Pclose"),
    SuppressUnmanagedCodeSecurity, SecuritySafeCritical]
    [UnmanagedCallConv(CallConvs = new Type[] { typeof(CallConvCdecl) })]
    public static partial herr_t close(hid_t plist);

I'm surprised to see that the generated code still uses DllImport

    internal static unsafe partial class H5P
    {
        [System.Runtime.InteropServices.DllImportAttribute("hdf5", EntryPoint = "H5Pclose", ExactSpelling = true)]
        public static extern partial int close(long plist);
    }

Is this correct/expected?

[alexrp]

Yes. The goal isn't to avoid DllImport, it's to avoid runtime marshaling of parameters and return values. The generated DllImport-decorated method will only use blittable types, while the wrapper does marshaling through source generation before/after calling it.

[PhilPJL]

Ok, I see. Thanks.