[erlang-questions] Turning on ASSERT's in OTP code.

[Rapsey]

I'm using a NIF library that sends messages from a thread and have not seen
such crashes.
The environment gets invalidated after a send. Are you calling
enif_clear_env or enif_free_env after enif_send?


Sergej

On Mon, Jun 28, 2010 at 8:12 AM, Paul Davis <paul.joseph.davis@REDACTED>wrote:

> I've stumbled across a weird segfault when sending terms from a thread
> spawned by a NIF. Investigating this i followed a traceback to
> erts/emulator/beam/erl_alloc_util.c. Glancing at the code in
> erl_alloc_util.c I notice that the line before the crash is an assert.
> Checking the value in gdb shows that the assertion is violated. My
> first thought was to try and enable these asserts but I'm not sure
> where to look for docs on how to do such a thing. Looking through the
> code I see them looking for DEBUG to be defined yet nothing in
> ./configure's help suggests a flag to set.
>
> In the interest of trying things I tried CFLAGS="-DDEBUG" ./configure
> && CFLAGS="-DDEBUG" make but it dies with an error about pcre.
>
> Anyone have a pointer on where to look for getting these enabled?
>
> Here's a copy of the traceback if it helps anyone. The lines in
> erl_alloc_util.c starting at 598:
>
>    ASSERT(crr->prev);
>    crr->prev->next = crr->next;
>
> gdb shows that crr is valid and crr->prev is NULL.
>
> #0  0x08085e82 in unlink_carrier (allctr=0xa2dc140, blk=<value optimized
> out>)
>    at beam/erl_alloc_util.c:599
> #1  destroy_carrier (allctr=0xa2dc140, blk=<value optimized out>)
>    at beam/erl_alloc_util.c:1615
> #2  0x08087161 in do_erts_alcu_free (type=148, unused=0x8250b60,
> p=0xa2dd7f0)
>    at beam/erl_alloc_util.c:2648
> #3  erts_alcu_free_thr_pref (type=148, unused=0x8250b60, p=0xa2dd7f0)
>    at beam/erl_alloc_util.c:2699
> #4  0x081535da in erts_free (env=0xa2dd7f0) at beam/erl_alloc.h:210
> #5  enif_free_env (env=0xa2dd7f0) at beam/erl_nif.c:256
> #6  0x00e21218 in job_destroy (obj=0xa2dd7c0) at c_src/job.c:32
> #7  0x00e21cda in queue_done (queue=0xa2dd718, item=0xa2dd7c0)
>    at c_src/queue.c:184
> #8  0x00e23849 in worker_exec (vm=0xa2a7d10) at c_src/worker.c:124
> #9  0x00e2376d in worker_run (arg=0xa2dd628) at c_src/worker.c:85
> #10 0x081d2a2c in thr_wrapper (vtwd=0xb64e5020) at common/ethread.c:480
> #11 0x0068296e in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
> #12 0x00260a4e in clone () from /lib/tls/i686/cmov/libc.so.6
>
>
> Thanks,
> Paul Davis
>
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