Re: Using vdr-dpg package for bug hunting?

Am 15.11.24 um 19:25 schrieb Marko Mäkelä:
> Thu, Nov 14, 2024 at 01:37:42PM +0100, schorpp wrote:
>> Hello,

Hi,

>>
>> I'm about fixing this old BUG exiting VDR on every 1st recording start:
>>
>> # gdb attach <pid of vdr>
>>
>> Program received signal SIGFPE, Arithmetic exception.
>> [Switching to Thread 0x9c801b40 (LWP 8182)]
>> 0x08136f6a in cFrameDetector::Analyze(unsigned char const*, int) ()
>> (gdb) bt
>> #0  0x08136f6a in cFrameDetector::Analyze(unsigned char const*, int) ()
> 
> On Debian and many other GNU/Linux distributions, executables are 
> without debug symbols by default. The debug symbols are separately 
> available in another repository, which you can add to a file in
> /etc/apt/sources.list.d:
> 
> deb http://deb.debian.org/debian-debug/ bookworm-debug main
> 
> (Replace bookworm with your Debian version of choice.)
> 
> After an apt-update, you should be able to execute
> 
> sudo apt install vdr-dbgsym
> 
> to get some files under /usr/lib/debug/.build-id/ that should match the 
> BuildID that should be reported by the following command:
> 
> file /usr/bin/vdr
> 
> That said, sometimes it is possible to find the bug by executing simply 
> the following commands in GDB:
> 
> disassemble 0x08136f6a
> info registers
> 
> If GDB complains that it does not know the function boundaries, you can 
> try to start disassembly from a few bytes earlier:
> 
> x/32i 0x08136f50

cool, thanks, i forgot so many things :-)

> 
> Hopefully this will show the problem, and this is easy enough to match 
> with the source code. If not, the debugging symbols for your vdr 
> executable should help you to produce a fully resolved stack trace 
> including the values of local variables (backtrace full).
> 
>> I've installed the vdr-dbg debian package to provide debugging symbols
> 
> I can't find a package with that name at https://packages.debian.org.

$ apt-cache policy vdr-dbg
vdr-dbg:
   Installiert:           2.0.6-6yavdr1~woprr
   Installationskandidat: 2.0.6-6yavdr1
   Versionstabelle:
      2.0.6-6yavdr1 0
         995 http://ppa.launchpad.net/yavdr/stable-vdr/ubuntu/ 
precise/main i386 Packages
  *** 2.0.6-6yavdr1~woprr 0
         100 /var/lib/dpkg/status
      2.0.3-3 0
         500 http://archive.debian.org/debian/ jessie/main i386 Packages
      1.7.28-1 0
         500 http://archive.debian.org/debian/ wheezy/main i386 Packages

$ diff -U3 /usr/sbin/runvdr.precise /usr/sbin/runvdr
--- /usr/sbin/runvdr.precise	2014-07-20 02:47:00.000000000 +0200
+++ /usr/sbin/runvdr	2024-11-15 10:08:21.700827294 +0100
@@ -7,7 +7,7 @@
     VDR_ENV="$VDR_ENV VDR_CHARSET_OVERRIDE=$VDR_CHARSET_OVERRIDE"
  fi

-VDRCMD="$VDR_ENV /usr/bin/vdr $*"
+VDRCMD="$VDR_ENV /usr/bin/vdr-dbg $*"

did the trick

Attaching to process 29155
Reading symbols from /usr/bin/vdr...Reading symbols from 
/usr/lib/debug/.build-id/10/e8b576883246ca77ad6f40e2c26053ba2d357c.debug...done.
done.

bt full / thread apply all bt
#2  0x081330f4 in cRemote::Get (WaitMs=10, UnknownCode=0x0) at remote.c:194
         MutexLock = {mutex = 0x822feb0, locked = true}
#3  0x080f225b in cInterface::GetKey (this=0x9ee02c8, Wait=<optimized 
out>) at interface.c:41
No locals.
#4  0x080aeda3 in main (argc=0, argv=<optimized out>) at vdr.c:1066
         Now = 1731696012
         Interact = <optimized out>
         key = <optimized out>
         PreviousChannelIndex = 0
         LastChannelChanged = 1731695003
         IsInfoMenu = false
         Menu = 0x0
         LastChannel = 18
         LastTimerChannel = 54
         PreviousChannel = {18, 2}
         CurrentSkin = <optimized out>
         LastInteract = 1731696012
         MaxLatencyTime = 6
         InhibitEpgScan = false
         VideoDirectory = 0x38 <Address 0x38 out of bounds>
         ResourceDirectory = 0x8194440 "/usr/share/vdr"
         EpgDataFileName = <optimized out>
         AudioCommand = 0x0
         CacheDirectory = 0x8194431 "/var/cache/vdr"

...

Strange is the the bug does no more occur using the vdr-dbg exe?
Maybe some left over debug break point or C++ assertion...

> 
> Best regards,
> 
>      Marko

y
tom