struct NestedLoopArg* args = (NestedLoopArg*)calloc(2, sizeof(NestedLoopArg));

args[0].ptr_type            = 0;  /* array */
args[0].ptr.array.elem_size = sizeof(int);
args[0].ptr.array.length    = 5;
args[0].ptr.array.ptr       = calloc(arg[0].array.length, arg[0].array.elem_size);

args[1].ptr_type            = 1;  /* func */
args[1].ptr.func.ptr        = my_func;
struct MyFuncPad arg1_pad;
arg1_pad.count = 5;
args[1].ptr.func.pad        = &arg1_pad;

NestedLoops(args);

... free memory allocated for args ...