module built with debugging symbols but backtrace: 0x00000050 in ?? ()

module built with debugging symbols but backtrace: 0x00000050 in ?? ()

[Jack Bates]

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I am trying to debug an Apache module. I compiled it with "-g", however
the first line of my backtrace is:

(gdb) bt
#0  0x00000050 in ?? ()
#1  0xb782f852 in call_get_cert_callback (session=0x81e5550, issuers_dn=0x0, 
    issuers_dn_length=0, pk_algos=0x0, pk_algos_length=0) at auth_cert.c:430
#2  0xb782fd1b in _gnutls_server_select_cert (session=0x81e5550, 
    requested_algo=4294967295) at auth_cert.c:1811
[...]

Here is a complete log of compiling and debugging the module:
http://cgi.sfu.ca/~jdbates/tmp/mod-gnutls/200809120/screenlog

I think that the module was built with debugging symbols. Here is the
output from "readelf -w":
http://cgi.sfu.ca/~jdbates/tmp/mod-gnutls/200809150/screenlog

I apologize - I am a gdb novice - my question is: If the module was
built with debugging symbols, why can't I tell from the first line of
the backtrace, where in the module's source code is this segmentation
fault? Why is the first line of the backtrace: 0x00000050 in ?? () -
instead of something more descriptive?

Here is the tread discussing this segmentation fault on
modules@outoforder.cc:
http://lists.outoforder.cc/pipermail/modules/2008-September/000164.html

Thank you! Jack

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Re: module built with debugging symbols but backtrace: 0x00000050 in ?? ()

[Daniel Jacobowitz]

On Mon, Sep 15, 2008 at 11:28:22AM -0700, Jack Bates wrote:
> I am trying to debug an Apache module. I compiled it with "-g", however
> the first line of my backtrace is:
> 
> (gdb) bt
> #0  0x00000050 in ?? ()

That's not a valid address for a function.  Usually, this means you've
called something that was not a valid function pointer.  Go up to
frame 1:

> #1  0xb782f852 in call_get_cert_callback (session=0x81e5550, issuers_dn=0x0, 
>     issuers_dn_length=0, pk_algos=0x0, pk_algos_length=0) at auth_cert.c:430

And see what it's trying to call.

-- 
Daniel Jacobowitz
CodeSourcery