Sharing memory between SV and DPI-C methods

Someone just asked me how to malloc() memory in a DPI-C import task (his reference model) such that the memory could be shared with the calling SV code. Because SV has some extra gubbins to track the array's properties, you cannot just use malloc() in C; even if you pass the pointer as an open array handle to the SV caller, SV won't know that you changed the array size.
A simple solution to this is to create a DPI-C export task in SV, that does the malloc for you in the SV domain.
Your C code can then call this function and use the array just as though you'd use C's malloc(), with the benefit that SV is aware of the array.

Here's an example.
// dpi.c
#include "svdpi.h"
#include <stdio.h>
#include <stdlib.h>
#include "vpi_user.h"

extern void allocate_mem ( int size );

void ref_model ( svOpenArrayHandle p )
{
  int unsigned *pp;
  int i;
  vpi_printf("c: Ref model started\n");
  allocate_mem(10);
  pp = ( int unsigned * ) svGetArrayPtr(p);
  for(i=0;i<10;i++) {
    pp[i] = i+1;
    vpi_printf("c: pp[%0d]=%0d\n",i,i+1);
  }
  vpi_printf("c: Ref model finished\n");
}

// dpi.sv
module top;
  typedef int unsigned mem_t;
  mem_t mem[];

  import "DPI-C" context task ref_model ( inout mem_t m[] );
  export "DPI-C" task allocate_mem;

  task allocate_mem ( input int size );
    $display("SV: allocating new SV DA of size %0d", size);
    mem = new[size];
  endtask

  initial begin
    ref_model(mem);
    $display("SV: ref model finished, mem.size()=%0d", mem.size());
    foreach (mem[i]) $display("SV: mem[%0d]=%0d", i,mem[i]);
  end
endmodule

And here's the corresponding output from "irun dpi.c dpi.sv"

c: Ref model started
SV: allocating new SV DA of size 10
c: pp[0]=1
c: pp[1]=2
c: pp[2]=3
c: pp[3]=4
c: pp[4]=5
c: pp[5]=6
c: pp[6]=7
c: pp[7]=8
c: pp[8]=9
c: pp[9]=10
c: Ref model finished
SV: ref model finished, mem.size()=10
SV: mem[0]=1
SV: mem[1]=2
SV: mem[2]=3
SV: mem[3]=4
SV: mem[4]=5
SV: mem[5]=6
SV: mem[6]=7
SV: mem[7]=8
SV: mem[8]=9
SV: mem[9]=10

Enjoy!