Question

There is no difference in argument passing between calls from SystemVerilog to C and calls from C to System- Verilog. Tasks and functions exported from SystemVerilog cannot have open arrays as arguments. Apart from this restriction, the same types of formal arguments can be declared in SystemVerilog for exported tasks and functions and imported tasks and functions. A task or function exported from SystemVerilog shall have the same function header in C as would an imported function with the same function result type and same formal argument list. In the case of arguments passed by reference, an actual argument to SystemVerilog task and function called from C shall be allocated using the same layout of data as SystemVerilog uses for that type of argument; the caller is responsible for the allocation. It can be done while preserving the binary compatibility, see Annex E.11.5 and Annex E.11.11.

Calling a SystemVerilog task from C is the same as calling a SystemVerilog function from C with the exception that the return type of an exported task is an int value which has a special meaning related to disable statements. Please see Section 27.8 for details on disable processing by DPI imported tasks and functions.