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

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

Thank you Ed! You're a swell guy, as they say in the 50's.

I will reply to you next week, when I get a chance to actually perform
these steps.

--Sam

On Mon, May 16, 2016 at 12:25 PM, Ed Maste <em...@fr...> wrote:
> On 15 May 2016 at 22:05, Sam Habiel <sam...@gm...> wrote:
>>
>> 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:
>
> Sorry about that - I wasn't sure how much or little detail to provide.
> I'm happy to work through the details with you.
>
>> 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?
>
> That's correct.
>
> jkoshy@ and others developed the BSD-licensed libelf in FreeBSD
> starting in the mid-2000s, and it's still that version that's in
> FreeBSD 10.
>
> libelf and other tools moved from FreeBSD to the ELF Tool Chain
> project  out to ELF Tool Chain later on, and were reimported into
> FreeBSD for FreeBSD 11.
>
>> 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).
>
> You can get it here:
> svn checkout svn://svn.code.sf.net/p/elftoolchain/code/trunk elftoolchain-code
> A top level 'make' will build libelf, libdwarf, and ELF Tool Chain
> versions of strip, nm, size, etc.
>
> Adding -L (and -I) options to CFLAGS when building your software
> should be sufficient to pick it up. You mentioned that it works with a
> libelf from ports, and the same scheme used to build against that one
> should work for your own elftoolchain build.
>
>> 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?
>
> Yes. You can build the library with -g, and -O0 to make debugging work
> better. E.g., with flags for 2. and 3.:
> CFLAGS="-g -O0 -L/example/src/elftoolchain/libelf
> -I/example/src/elftoolchain/libelf" make
>
> You can set a breakpoint on elf_update, and then step through to find
> out where the error is returned.



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