[LAU] reporting a bug: getting a backtrace

[Robin Gareus]

On 01/17/2012 10:27 PM, Renato wrote:
> Hi, I'm getting a consistent crash in ams I'd like to report, but for it
> to be useful I think I have to provide a backtrace, right? 
> 
> How do I compile ams to get that? I don't see any "debug" option or
> similar in ./configure --help...
>

Hi Renato,

You need to compile the program with gcc's '-g' option in order to
produce useful backtraces. Some software has this flag turned on by
default (check the output of `make`) but duplicating it does not hurt.

With most autotools' configured projects you can that with environment
variables:
  CFLAGS=-g CXXFLAGS=-g ./configure

(Custom configure scripts often accept '--with-cflags=-g' or similar
options - usually documented in ./INSTALL)


Next run the program under the GNU debugger:

gdb --args ./path/to/binary [options]
## inside gdb:
run
## wait until it crashes, then type
thread apply all bt
## and send the output upstream.


gdb slows things down. If the application-under-test is a jack-client:
It may cause jack-timeouts and eventually jackd may kick out the client
(You should not be running jackd with realtime privileges at the same
time as jack-client under gdb). An Alternative to running the program
inside the debugger is to create core-dump of the crash, and later
analyze the dump with gdb:

ulimit -c unlimited
./my/bad/program
## crash
ls -l core.XXXXX
gdb ./my/bad/program core.XXXXX
thread apply all bt


HTH,
robin