Re: getting the line of a function when walking the stack with libbfd

[Vincent Torri <vincent dot torri at gmail dot com>]

Hey

On Fri, Mar 23, 2012 at 10:24 AM, Alan Modra <amodra@gmail.com> wrote:
> On Fri, Mar 23, 2012 at 08:47:25AM +0100, Vincent Torri wrote:
>> Is there a way to get the frames with libbfd?
>
> No. ?It's not hard to write for one ABI. ?For example, see
> glibc/debug/backtrace.c.

I have modified the code a bit to create a shared lib and a test
program (see attached archive). All the tests below are done in linux
(arch: i686, in case it's important)

i've tested a bit, using addr2line with the addresses that the glibc
code returns. It's not perfect, it even depends on the optimization
flag I pass.

In the test program (it's actually the backtrace test program of
glibc) , there are 2 functions: compress() (which calls the backtrace
function) and main() which calls compare()

If I pass no optimization flag:

1) the line returned by addr2line with the first address is the line
where the backtrace function is called, so it's good.
2) the line returned by addr2line with the second address is *not* the
line where the compress() function is called (compress() is called 2
line below.)

If I pass -O2:

1) the line returned by addr2line with the first address is *not* the
line where the backtrace function is called (backtrace() is called 1
line below.)
2) the line returned by addr2line with the second address is the line
where the compress() function is called,  so it's good.

Is it normal to not get the correct lines ?

Vincent

Attachment: bt.tar.bz2
Description: BZip2 compressed data