bug#17817: 24.3.91; Assertion failure in bidi.c (Cygwin-w32 build)

[Ken Brown]

On 6/20/2014 3:21 PM, Eli Zaretskii wrote:
> > Date: Fri, 20 Jun 2014 14:42:05 +0100
> > From: Ken Brown <kbrown@cornell.edu>
> >
> > I just got the following assertion failure:
> >
> >     bidi.c:329: Emacs fatal error: assertion failed: UNKNOWN_BT <= type
> > && type <= NEUTRAL_ON
>
> Is this the same 64-bit Cygwin-w32 build that was reported lately to
> produce nonsensical backtraces?

Yes.

> > #0  terminate_due_to_signal (sig=6, backtrace_limit=2147483647) at emacs.c:351
> > No locals.
> > #1  0x00000001005ba95d in die (
> >      msg=0x100a2e538 <DEFAULT_REHASH_SIZE+64> "UNKNOWN_BT <= type && type <= NEUTRAL_ON", 
> > file=0x100a2e530 <DEFAULT_REHASH_SIZE+56> "bidi.c", line=329)
> >      at alloc.c:6826
> > No locals.
> > #2  0x00000001004fb4fe in bidi_check_type (type=STRONG_L) at bidi.c:329
> > No locals.
> > #3  0x0000000100500630 in bidi_level_of_next_char (bidi_it=0x2267d8)
> >      at bidi.c:2430
> >          type = STRONG_L
> >          level = 0
> >          prev_level = 0
> >          next_for_neutral = {
> >            bytepos = 0,
> >            charpos = -1,
> >            type = UNKNOWN_BT,
> >            type_after_w1 = UNKNOWN_BT,
> >            orig_type = UNKNOWN_BT
> >          }
> >          next_char_pos = 1
>
> This makes no sense at all: STRONG_L is one of the bidi types defined
> by 'enum bidi_type_t' (see dispextern.h), and therefore its value
> _must_ be between UNKNOWN_BT (whose value is zero) and NEUTRAL_ON, the
> last tag in the enumeration type.
>
> Can you see the numerical value of 'type' in frame #2?  Like this:
>
>   (gdb) fr 2
>   (gdb) p type + 0
> Also, using a similar technique, display the values of UNKNOWN_BT and
> of NEUTRAL_ON.

(gdb) p type + 0
$2 = 1
(gdb) p UNKNOWN_BT + 0
$3 = 0
(gdb) p NEUTRAL_ON + 0
$4 = 23

So, as you said, this is nonsense.

Ken