[DVDnav-discuss] Bug report for specific DVD

[gnosygnu]

On Fri, Aug 15, 2014 at 12:23 PM, Michael Russo <greatquux at gmail.com> wrote:

> That did help and I was now able to compile libdvdnav with TRACE defined.
>  I still ran vlc through gdb in order to get a backtrace.  There was a LOT
> of tracing going on, and now the SIGSEGV occurred inside of printf()
> because it was trying to print out the invalid memory address.   Hopefully
> there's something here you can use to track down what's going on.  It's
> likely some weird form of copy protection.
>

Hi. I took a look at the log file, but am not able to make much of the
cause. I summarize some points below. Hopefully someone else can help.

----

>From the log below, it looks like it tries to jump to the root menu, and
then hits a recursive loop.

* The same 3 lines repeat over and over again in the call stack (see below)
* The bulk of the log has the same repeating section.
** It starts with "play_PGC: (vm->state).pgcN (1)"
** 28 lines later, it ends with "** Fell of the end of the pgc, continuing
in NextPGC"
* When it fails, it fails on vm_print_registers. Note that
vm_print_registers is responsible for the register dump ("libdvdnav:
#     0 |  1 |  2 |  3..."). It had worked on each of the previous 13700+
iterations, so I'm assuming there's some sort of out of memory issue when
it finally fails.

Due to the PGC messages, I'd guess that the problem is somewhere in the IFO
files. (It's basically trying to find a title to start at). However, I
can't think of any particular way to identify what's wrong from the
libdvdnav point of view...

#5  vm_print_registers (registers=0x7fffb4056e28) at src/vm/decoder.c:768
#6  0x00007ffff7bcd4ee in vmEval_CMD (commands=0x7fffb40086a0,
num_commands=4,
    registers=registers at entry=0x7fffb4056e28,
return_values=return_values at entry=0x7fffeb8f7ee0)
    at src/vm/decoder.c:597
#7  0x00007ffff7bd06c2 in play_PGC (vm=vm at entry=0x7fffb4056e10) at
src/vm/play.c:72
....
#13778 0x00007ffff7bd07e0 in play_PGC_post (vm=vm at entry=0x7fffb4056e10) at
src/vm/play.c:153
#13779 0x00007ffff7bd0542 in play_PG (vm=vm at entry=0x7fffb4056e10) at
src/vm/play.c:168
#13780 0x00007ffff7bd0675 in play_PGC (vm=vm at entry=0x7fffb4056e10) at
src/vm/play.c:83
#13781 0x00007ffff7bd07e0 in play_PGC_post (vm=vm at entry=0x7fffb4056e10) at
src/vm/play.c:153
#13782 0x00007ffff7bd0542 in play_PG (vm=vm at entry=0x7fffb4056e10) at
src/vm/play.c:168
#13783 0x00007ffff7bd0675 in play_PGC (vm=vm at entry=0x7fffb4056e10) at
src/vm/play.c:83
#13784 0x00007ffff7bd00f0 in vm_jump_menu (vm=vm at entry=0x7fffb4056e10,
menuid=menuid at entry=DVD_MENU_Title)
    at src/vm/vm.c:647
#13785 0x00007ffff7bcae2b in dvdnav_menu_call (this=0x7fffb4002480,
menu=menu at entry=DVD_MENU_Title)
    at src/searching.c:489
#13786 0x00007fffec80dab8 in Open (p_this=0x7fffb4008798) at dvdnav.c:342