[lttng-dev] Request change name of function lookup_enum in libbabeltrace to make GDB use this lib

Thu Dec 20 08:46:37 EST 2012

On Tue, Dec 11, 2012 at 11:18 PM, Hui Zhu <teawater at gmail.com> wrote:
> On Mon, Dec 10, 2012 at 10:05 PM, Mathieu Desnoyers
> <mathieu.desnoyers at efficios.com> wrote:
>> * Hui Zhu (teawater at gmail.com) wrote:
>>> On Thu, Dec 6, 2012 at 11:57 PM, Pedro Alves <palves at redhat.com> wrote:
>>> > On 12/05/2012 12:08 PM, Mathieu Desnoyers wrote:
>>> >> * Hui Zhu (teawater at gmail.com) wrote:
>>> >>> Hi,
>>> >>>
>>> >>> I am working on add CTF support to GDB.  You can see my patch review threads in:
>>> >>> http://sourceware.org/ml/gdb-patches/2012-11/msg00552.html
>>> >>> http://sourceware.org/ml/gdb-patches/2012-11/msg00554.html
>>> >>> http://sourceware.org/ml/gdb-patches/2012-11/msg00553.html
>>> >>> http://sourceware.org/ml/gdb-patches/2012-11/msg00555.html
>>> >>> http://sourceware.org/ml/gdb-patches/2012-11/msg00556.html
>>> >>>
>>> >>> To make GDB support CTF read, I use libbabeltrace with GDB.  You can
>>> >>> see the patch in
>>> >>> http://sourceware.org/ml/gdb-patches/2012-11/msg00555.html.
>>> >>> I have a issue is  libbabeltrace have a function called lookup_enum
>>> >>> that is same with a GDB function.
>>> >>> I change the function name of GDB to handle this issue in my patch.
>>> >>>
>>> >>> But Tom said let libbabeltrace to change function name is better.
>>> >>> So I send this mail to ask do you mind change the function name of
>>> >>> lookup_enum?   If you can change the function name that will be really
>>> >>> helpful for us.  Thanks a lot.
>>> >>> And I post a patch about change the function name in libbabeltrace.
>>> >>
>>> >> I'm CCing Julien Desfossez on this one. From what I see,
>>> >> include/babeltrace/types.h is not included into the system, so it should
>>> >> not be considered to be a public header of libbabeltrace.
>>> >
>>> > I've just built and installed babeltrace 1.0.0 (where's the mainline repository,
>>> > BTW?), and indeed, I'm not seeing the types.h file anywhere in the
>>> > installed tree:
>>> >
>>> > $ ~/src/babeltrace/install/include> find
>>> > .
>>> > ./babeltrace
>>> > ./babeltrace/trace-handle.h
>>> > ./babeltrace/list.h
>>> > ./babeltrace/babeltrace.h
>>> > ./babeltrace/context.h
>>> > ./babeltrace/iterator.h
>>> > ./babeltrace/ctf
>>> > ./babeltrace/ctf/callbacks.h
>>> > ./babeltrace/ctf/events.h
>>> > ./babeltrace/ctf/iterator.h
>>> > ./babeltrace/format.h
>>> > ./babeltrace/clock-types.h
>>> >
>>> > The GDB patch is including types.h explicitly:
>>> >
>>> > +#ifdef HAVE_LIBBABELTRACE
>>> > +#include <babeltrace/babeltrace.h>
>>> > +#include <babeltrace/types.h>
>>> > +#include <babeltrace/ctf/events.h>
>>> > +#include <babeltrace/ctf/iterator.h>
>>> >
>>> > So indeed, Hui, you'll need to make sure your patch works against an
>>> > installed babeltrace, making sure it does not pick up headers
>>> > from babeltrace's source directory.  If there's really no reason to
>>> > include that types.h header (since it seems you don't really need any
>>> > function declared in that file), maybe there's actually nothing for
>>> > babeltrace to do.
>>>
>>> Oops, sorry for I miss something.
>>> I use include babeltrace/types.h because I use function
>>> get_int_signedness that defined inside it.
>>
>> Can you use:
>>
>> include/babeltrace/ctf/events.h: bt_ctf_get_int_signedness() instead ?
>>
>> This one is within an exported header,
>>
>> Thanks,
>>
>> Mathieu
>
> Great! My part is OK now.  Thanks for your help.
>
> Best,
> Hui
>

Hi Mathieu.,

I am so sorry that I still have issue with the function name of lookup_enum.
What I met is a crash when try to use libbabeltrace in GDB:
#0  0x00000000005d0cfc in block_static_block (block=0x7ffff6e5ee3e) at
../../gdb/gdb/block.c:343
#1  0x00000000005d42ae in lookup_symbol_aux_local (name=0xf70c70
"\240!\224\001", block=0x7ffff6e5ee3e,
    domain=STRUCT_DOMAIN, language=language_c) at ../../gdb/gdb/symtab.c:1429
#2  0x00000000005d40b5 in lookup_symbol_aux (name=0xf70c70
"\240!\224\001", block=0x7ffff6e5ee3e, domain=STRUCT_DOMAIN,
    language=language_c, is_a_field_of_this=0x0) at ../../gdb/gdb/symtab.c:1345
#3  0x00000000005d3cae in lookup_symbol_in_language (name=0xf70c70
"\240!\224\001", block=0x7ffff6e5ee3e,
    domain=STRUCT_DOMAIN, lang=language_c, is_a_field_of_this=0x0) at
../../gdb/gdb/symtab.c:1231
#4  0x00000000005d3cff in lookup_symbol (name=0xf70c70
"\240!\224\001", block=0x7ffff6e5ee3e, domain=STRUCT_DOMAIN,
    is_a_field_of_this=0x0) at ../../gdb/gdb/symtab.c:1246
#5  0x000000000062f372 in lookup_enum (name=0xf70c70 "\240!\224\001",
block=0x7ffff6e5ee3e)
    at ../../gdb/gdb/gdbtypes.c:1287
#6  0x00007ffff6e479b5 in ctf_read_event (ppos=0xf6cca8,
stream=0xf6cc10) at ../../../babeltrace/formats/ctf/ctf.c:434
#7  0x00007ffff7071204 in stream_read_event (sin=<optimized out>) at
../../babeltrace/lib/iterator.c:65
#8  0x00007ffff7071eb3 in bt_iter_init (iter=0x13ec820, ctx=0xf4b8b0,
begin_pos=0x7fffffffdad0, end_pos=<optimized out>)
    at ../../babeltrace/lib/iterator.c:703
#9  0x00007ffff6e4a6ac in bt_ctf_iter_create (ctx=0xf4b8b0,
begin_pos=0x7fffffffdad0, end_pos=0x0)
    at ../../../babeltrace/formats/ctf/iterator.c:53
#10 0x000000000050d4b1 in bt_ctf_open (dirname=0xd98c1b
"/home/teawater/gdb/ctf/kernel/") at ../../gdb/gdb/ctf.c:1289

You can see that when function ctf_read_event of libbabeltrace try to
call function lookup_enum.  It call the function of GDB.  Then it got
crash.

So could you help me with it?

Thanks,
Hui

>>
>>>
>>> Thanks,
>>> Hui
>>>
>>>
>>> >
>>> >> Julien, is there an publically exposed babeltrace API that performs
>>> >> something similar to the internal lookup_enum() ?
>>> >>
>>> >> Hui, are you using other functions from include/babeltrace/types.h ?
>>> >
>>> > --
>>> > Pedro Alves
>>> >
>>
>> --
>> Mathieu Desnoyers
>> Operating System Efficiency R&D Consultant
>> EfficiOS Inc.
>> http://www.efficios.com