Subject: Re: bug#30626: 26.0.91; Crash when traversing a `stream-of-directory-files'

From: Noam Postavsky <[email-masked]>
Date: Sat, 17 Mar 2018 11:53:36 -0400

Eli Zaretskii <[email-masked]> writes:

> In frame #4852, we have found an object, and we are marking it.  Did
> you try looking at that object?  With these caveats:
>
>> > Also note that for Lisp objects that are marked you need to reset
>> > their mark bit before trying to determine their type and value.

Okay, I think xpr takes care of that, right?  (I've restarted the debug
sessions a few times, so numbers may not match exactly)

#4853 0x000000000060f429 in mark_maybe_pointer (p=0x2e64c90) at ../../src/alloc.c:4936
4936		mark_object (obj);
(gdb) p obj
$60 = XIL(0x2e64c95)
(gdb) xpr
Lisp_Vectorlike
PVEC_NORMAL_VECTOR
$61 = (struct Lisp_Vector *) 0x2e64c90
{XIL(0x2efcb63), make_number(1000000), XIL(0x2efcb53), XIL(0x2efcb73), XIL(0x2efcb83), 
  XIL(0x20ab5b0), XIL(0xc090)}
(gdb) p $61->contents[0]
$62 = XIL(0x2efcb63)
(gdb) xpr
Lisp_Cons
$63 = (struct Lisp_Cons *) 0x2efcb60
{
  [...]
      car = make_number(2369), 
      [...]
        chain = 0x0
[...]
(gdb) p $61->contents[1]
$64 = make_number(1000000)
(gdb) p $61->contents[2]
$65 = XIL(0x2efcb53)
(gdb) xpr
Lisp_Cons
[...] car = make_number(1), [...] chain = 0x0 [...]
(gdb) p $61->contents[3]
$67 = XIL(0x2efcb73)
(gdb) xpr
[...] car = XIL(0xc090), [...] chain = 0x0 [...]
(gdb) p $61->contents[4]
[...] car = XIL(0x2efc443), [...] chain = 0x0 [...]
(gdb) p $61->contents[5]
[...]
$72 = (struct Lisp_Symbol *) 0x2e97ef0
"stream-range"
(gdb) p $61->contents[6]
[...]
$74 = (struct Lisp_Symbol *) 0xdf89d0 <lispsym+49296>
"t"

It looks like a the lexical environment of a bytecode function, probably
the initial stream, e.g., (stream-range 1 1000000) gives:

(--stream-- #[256 "\211\203\303\242\207\303\242\204 \304\300\242\305\300\242\302\242\\\301\302\242#B\240\210\303\306\240\210\304\242\207" 
              [(1) 1000000 (1) (nil) (nil) stream-range t] 7 "
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

(fn &optional CHECK)"])

Not sure where to go next with this.