Question

DPI allows calling SystemVerilog functions from another language. However, such functions must adhere to the same restrictions on argument types and results as are imposed on imported functions. It is an error to export a function that does not satisfy such constraints.

SystemVerilog functions that can be called from foreign code need to be specified in export declarations. Export declarations are allowed to occur only in the scope in which the function being exported is defined. Only one export declaration per function is allowed in a given scope.

Note that class member functions cannot be exported, but all other SystemVerilog functions can be exported.

Similar to import declarations, export declarations can define an optional c_identifier to be used in the foreign language when calling an exported function.

dpi_import_export ::=     // from Annex A.2.6
    | export "DPI" [c_identifier =] function function_identifier;

Syntax 27-2—DPI export declaration syntax (excerpt from Annex A)

c_identifier is optional here. It defaults to function_identifier. For rules describing c_identifier, see Section 27.3. Note that all export functions are always context functions. No two functions in the same SystemVerilog scope can be exported with the same explicit or implicit c_identifier. The export declaration and the definition of the corresponding SystemVerilog function can occur in any order. Only one export declaration is permitted per SystemVerilog function.