when use DPI, pass arrays of type byte to C function

[jimnan]

How to pass pass arrays of type byte to C function in Systemverilog DPI ?

Below are my test code, VCS seem convert char to int.
Why a[1]~ a[3] become 0 ?
They should be 3/5/7 respectively.
(LRM 3.1 spec. said SV could pass datatype byte as argument )

Can anyone try this code in modelsim or ncverilog ?


///// C code

int arr_read( char *a)
{
int i;
for(i=0; i<5; i++) {
printf("in c code , a[%d] =%d\n",i, a); }
}


///// system verilog codeimport "DPI-C" function arr_read(byte a[5]);
module test ();
byte array_src[5] = {2,3,5,7,9};
initial begin : t1_label
$display("array_src[0] is %h", array_src[0]);
$display("array_src[1] is %h", array_src[1]);
$display("array_src[2] is %h", array_src[2]);
arr_read(array_src, array_src2, error);
end : t1_labelendmodule

// output display

> array_src[0] is 02
> array_src[1] is 03
> array_src[2] is 05
> in c code , a[0] =2
> in c code , a[1] =0
> in c code , a[2] =0
> in c code , a[3] =0
> in c code , a[4] =3

 

[echo47]

I couldn't run your code due to various syntax errors and undefined variables. Try this:

import "DPI-C" function void arr_read(byte a[5]);
module test ();
  byte array_src[5] = '{2,3,5,7,9};
  initial begin : t1_label
    $display("array_src[0] is %h", array_src[0]);
    $display("array_src[1] is %h", array_src[1]);
    $display("array_src[2] is %h", array_src[2]);
    arr_read(array_src);
  end : t1_label
endmodule

#include <stdio.h>
void arr_read(char *a)
{
  int i;
  for(i=0; i<5; i++)
    printf("in c code , a[%d] =%d\n",i, a[i]);
}

I used MinGW to compile the C into a Windows DLL. Here is ModelSim's output:

# array_src[0] is 02
# array_src[1] is 03
# array_src[2] is 05
# in c code , a[0] =2
# in c code , a[1] =3
# in c code , a[2] =5
# in c code , a[3] =7
# in c code , a[4] =9

Interesting little experiment! This is the first time I've tried SystemVerilog and DPI.

 

[jimnan]

Hi echo47,
Thanks for your testing!
I thnink VCS has problem when pass datatype byte array.
And I'm waiting for their reply.

SV co-work with C is powerful ~
^_^

 

[darylz]

Sure, SV co-work with C/C++ is very powerful...
But presently, in the simulation env, it's very difficult to debug C/C++...