Re: [Elftoolchain-developers] elf_update() returns error "Invalid data buffer descriptor" on FreeBSD 10.3

[Sam H. <sam...@gm...>]

Ed, thank you for your reply.

It will take me a while to get back to you... as this is a hobby thing
and I will get back to it when I get a chance.

Having said that though, I don't have enough experience in FreeBSD to
be able to answer all your questions; and I never had to use gdb to
debug a linked library before. Let me answer and ask in turns:

1. I downloaded FreeBSD 10.3 and libelf came with the system without
me installing anything. I presume then it's in the FreeBSD source tree
since I didn't install that one from the ports tree, correct?
2. Where is the upstream version? And how can I compile it to replace
the ones that my makefile grabs? (I think I can figure this one out,
but a hint will help).
3. How do use gdb to step into such a library? Would just typing "s"
take you into the code if everything else is in place?

--Sam

On Sun, May 15, 2016 at 4:47 PM, Ed Maste <em...@fr...> wrote:
> On 15 May 2016 at 16:43, Sam Habiel <sam...@gm...> wrote:
>> First time on list,
>>
>> Failure here: https://github.com/shabiel/fis-gtm/blob/freebsd/sr_x86_64/obj_filesp.c#L322
>>
>> I added a line after it:
>>                 FPRINTF(stderr, elf_errmsg(elf_errno()));
>>
>> And this line says: Invalid data buffer descriptor.
>>
>> Ports tree libelf doesn't have this problem.
>>
>> root@:~/repos/fis-gtm # uname -a
>> FreeBSD  10.3-RELEASE FreeBSD 10.3-RELEASE #0 r297264: Fri Mar 25
>> 02:10:02 UTC 2016
>> ro...@re...:/usr/obj/usr/src/sys/GENERIC  amd64
>
> To confirm, this is the libelf in the FreeBSD source tree, not the
> upstream elftoolchain version? If so, can you test the upstream
> version? I don't anticipate any differences, but it will be a better
> base for experimentation and debugging.
>
> I see three
> LIBELF_SET_ERROR(DATA, 0);
> in libelf/elf_update.c. If you can run the application under a
> debugger I would set a breakpoint on them and see which case returned
> the error, which should give a suggestion on next steps.
>
> -Ed



-- 
Sam Habiel, Pharm.D.
VISTA Expertise Network