[erlang-questions] how can I debug errors in linked-in drivers or nif loaded as shared library?

[caox]

hi

I got a segmentation fault and a core.dump file when tested my linked-in driver. How could I debug it with gdb?
For an executable c file, we can just call 'gdb a.out core.dump'. How can I do this for a .so file loaded by erlang?
Thanks.
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[Attila Rajmund Nohl]

2010/12/24, caox <ca...@lightpole.net>:

> hi
>
> I got a segmentation fault and a core.dump file when tested my linked-in
> driver. How could I debug it with gdb?
> For an executable c file, we can just call 'gdb a.out core.dump'. How can I
> do this for a .so file loaded by erlang?

If I remember correctly, you should use the path to the erl binary in
place of 'a.out'.

[Kevin A. Smith]

I've edited the erl script which comes with the standard Erlang release to allow easy use of GDB for just such situations:

if [ ! -z "$USE_GDB" ]; then
gdb $BINDIR/erlexec --args $BINDIR/erlexec ${1+"$@"}
else
exec $BINDIR/erlexec ${1+"$@"}
fi

#exec $BINDIR/erlexec ${1+"$@"}

Define the env var "USE_GDB" before launching Erlang and you'll get a debugger prompt when your NIF/driver crashes. GDB's backtrace command is especially helpful :-)

Credit to Dave Smith @ Basho for originally suggesting this approach.

--Kevin

[caox]

thanks a lot. I will try it.