incomplete disassembly?

[Robert Brown]

When I compile and load the following function

(defun doit2 (x)
  (declare (type fixnum x)
           (optimize (speed 3) (safety 0)))
  (labels ((even (x)
             (declare (type fixnum x))
             (if (zerop x)
                 t
                 (odd (- x 1))))
           (odd (x)
             (declare (type fixnum x))
             (if (zerop x)
                 nil
                 (even (- x 1)))))
    (list (even x) (odd x))))

then execute (disassemble 'doit2), the output includes "JMP L4" but there's no line of assembly code with an L4 label. Maybe the disassembly is truncated?

[Stas Boukarev (stassats)]

It's showing only the current function, if you want to see everything you need to use sb-disassem:disassemble-code-component.

[Robert Brown (robert-brown)]

Thanks very much. Also, sb-c:dis seems output what I was expecting.

[Fedorov Alexander (gleefre)]

I believe that it is a valid bug -- such "undefined" labels don't make any sense.

A bit of context:

Local functions are not shown by DISASSEMBLE since sbcl-2.2.1; or more exactly after this commit: https://github.com/sbcl/sbcl/commit/be5c6d037ba032717638f21d515444cf255e4cbd. As mentioned in its message:
> This makes previously visible local functions disappear, but they were not consistently included either.

I think that the next sentence could've been a FIXME instead:
> A different mechanism is needed to decide whether a local function is called by the target function.

A fuller example:

* (defun foo ()
    (labels ((rec (l) (and l (cons l (rec (cdr l))))))
      (rec '(1 2 3))))
FOO
* (disassemble 'foo)
; disassembly for FOO
; Size: 20 bytes. Origin: #x54E1025F ; FOO
; 5F: 498B4510 MOV RAX, [R13+16] ; thread.binding-stack-pointer
; 63: 488945F8 MOV [RBP-8], RAX
; 67: 488B35C2FFFFFF MOV RSI, [RIP-62] ; '(1 2 3)
; 6E: EB03 JMP L0 ; <----------- here!
; 70: 8F4508 POP QWORD PTR [RBP+8]

It can also be shown in a note -- when a function is compiled by a file compiler and then loaded:

;;;; foo.lisp
(defun foo ()
  (labels ((rec (x)
             (if (= x 0)
                 0
                 (1+ (rec (1- x))))))
    #'rec))

* (compile-file "foo")
; ...
* (load "foo")
T
* (disassemble 'foo)
; disassembly for FOO
; Size: 17 bytes. Origin: #x5515C08F ; FOO
; 8F: 498B4510 MOV RAX, [R13+16] ; thread.binding-stack-pointer
; 93: 488945F8 MOV [RBP-8], RAX
; 97: 8D150E000000 LEA EDX, [RIP+14] ; = L0 ; <----------- here!
; 9D: C9 LEAVE
; 9E: F8 CLC
; 9F: C3 RET
NIL

I tested this on both sbcl-master & sbcl-2.4.0; linux, x86-64.

uname -a:
Linux grolter-T16 6.2.0-39-generic #40-Ubuntu SMP PREEMPT_DYNAMIC Tue Nov 14 14:18:00 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux