DPI-C: passing string as an argument from C to SV task

SystemVerilog
,
1

Hello,
I am trying to pass a string from C to a SV task, but in SV domain, the string looks corrupted instead of alphabetical characters of the original value (“/home/dir/”) in C. Any idea why? Thanks.

extern "C" void Print_String_SV (string dir);
void Init_CSP_Mem_BD () { // this is a C function
    char *a_string = "/home/dir/";
    Print_String_SV (a_string);
}
module module_t ();
   export "DPI-C" task Print_String_SV;
   task Print_String_SV (string str);
       $display ("This is string value %s", str);
   endtask
endmodule
2

In reply to dnguyen82us:

I am surprised this even compiled for you. A C++
string is a class, not a pointer to a
char

extern "C"
int Init_CSP_Mem_BD();

extern "C" int
Print_String_SV( const char * str);

int Init_CSP_Mem_BD () {
  char a_string[] = "/home/dir/";
    Print_String_SV (a_string);
    return 0;
}

module module_t ();
   import "DPI-C" context task Init_CSP_Mem_BD();
   export "DPI-C" task Print_String_SV;
   task Print_String_SV (string str);
       $display ("This is string value %s", str);
   endtask : Print_String_SV
   initial Init_CSP_Mem_BD;
   
endmodule : module_t

Note that some tools can automatically generate the correct C prototypes as a header file that you can include. That way you are guaranteed to get a compiler error if you argument types do not match.