Debugger

Debugger

We added a debugger in v8.0. Use command ./nasal -dbg xxx.nas to use the debugger, and the debugger will print this:

source code:
--> var fib = func(x) {
        if (x<2) return x;
        return fib(x-1)+fib(x-2);
    }
    for(var i=0;i<31;i+=1)
        print(fib(i),'\n');


next bytecode:
    0x0003a8    07:00 00 00 00 00 00 00 00     pnil    0x0 (std/lib.nas:413)
    0x0003a9    56:00 00 00 00 00 00 00 00     ret     0x0 (std/lib.nas:413)
    0x0003aa    03:00 00 00 00 00 00 00 56     loadg   0x56 (std/lib.nas:413)
--> 0x0003ab    0b:00 00 00 00 00 00 03 af     newf    0x3af (test/fib.nas:1)
    0x0003ac    02:00 00 00 00 00 00 00 03     intl    0x3 (test/fib.nas:1)
    0x0003ad    0d:00 00 00 00 00 00 00 22     para    0x22 (x) (test/fib.nas:1)
    0x0003ae    3e:00 00 00 00 00 00 03 be     jmp     0x3be (test/fib.nas:1)
    0x0003af    45:00 00 00 00 00 00 00 01     calll   0x1 (test/fib.nas:2)

vm stack (0x7fca7e9f1010, limit 16, total 0)
>>

If want help, input h to get help.

When running the debugger, you could see what is on stack. This will help you debugging or learning how the vm works:

source code:
    var fib = func(x) {
-->     if (x<2) return x;
        return fib(x-1)+fib(x-2);
    }
    for(var i=0;i<31;i+=1)
        print(fib(i),'\n');


next bytecode:
    0x0003a8    07:00 00 00 00 00 00 00 00     pnil    0x0 (std/lib.nas:413)
    0x0003a9    56:00 00 00 00 00 00 00 00     ret     0x0 (std/lib.nas:413)
    0x0003aa    03:00 00 00 00 00 00 00 56     loadg   0x56 (std/lib.nas:413)
    0x0003ab    0b:00 00 00 00 00 00 03 af     newf    0x3af (test/fib.nas:1)
    0x0003ac    02:00 00 00 00 00 00 00 03     intl    0x3 (test/fib.nas:1)
    0x0003ad    0d:00 00 00 00 00 00 00 22     para    0x22 (x) (test/fib.nas:1)
    0x0003ae    3e:00 00 00 00 00 00 03 be     jmp     0x3be (test/fib.nas:1)
--> 0x0003af    45:00 00 00 00 00 00 00 01     calll   0x1 (test/fib.nas:2)

vm stack (0x7fca7e9f1010, limit 16, total 8)
  0x000007    | pc   | 0x3c7
  0x000006    | addr | 0x0
  0x000005    | nil  |
  0x000004    | nil  |
  0x000003    | num  | 0
  0x000002    | nil  |
  0x000001    | nil  |
  0x000000    | func | <0x5573f66ef5f0> func(elems...) {..}
>>

Also you could use r to see the status of vm registers:

>> r
registers (main)
  [pc    ]    | pc   | 0x3af
  [global]    | addr | 0x7fca7e8f0010
  [local ]    | addr | 0x7fca7e9f1030
  [memr  ]    | addr | 0x0
  [canary]    | addr | 0x7fca7eaf0ff0
  [top   ]    | addr | 0x7fca7e9f1080
  [funcr ]    | func | <0x5573f66ec1f0> func(x) {..}
  [upval ]    | nil  |
>>