[Qt-creator] libgdbmacros.so won't get loaded fordebuggedapplication

[Eike Ziller]

Hm, now I see that the thread somehow got split up in my mail client,
so I didn't see that you already found a solution, please ignore me :)

++ Eike

On Jan 5, 2009, at 12:47 PM, Ziller Eike (Nokia-D-Qt/Berlin) wrote:

> On Dec 30, 2008, at 10:08 PM, ext Illich Jan wrote:
>
>> Andre Poenitz wrote:
>>>
>>>> 1. On an older systems (CentOS 4.6) the libgdbmacros.so won't get
>>>> loaded into the debugged application. I know that the  
>>>> distribution's
>>>> gdb (old 6.3 version) is not supported, but I have relatively
>>>> up-to-date versions of development tools installed (Qt 4.4.1, gdb
>>>> 6.7.1, gcc 4.1.2). Debugged app is linked against Qt 4.4.1.
>>>
>>> I assume that Options -> Debugger -> Gdb  points to the 6.7.1 gdb...
>>>
>>> Could you check whether 'ldd libgdbmacros.so.1.0.0' does not yield
>>> unresolved libraries, and also whether the Qt version it points to
>>> is the same as the one used by your application?
>>
>> I've dug around a bit and found out that it's some sort of dynamic
>> linker or gdb symbol resolver issue (even upgrading to latest gdb
>> 6.8 did not help).
>>
>> When qtcreator tries to send 'call dlopen("...libgdbmacros"...)' to
>> gdb, gdb responds 'No symbol "dlopen" in current context.'
>>
>> As a temporary workaround, dlopen()ing libgdbmacros.so in debugged
>> app's main() makes it work (Qt structures are shown correctly then).
>>
>> For some obscure reason, gdb cannot resolve 'dlopen' symbol, only
>> dlopen's procedure linkage table (PLT) proxy 'dlopen at plt'. I tried
>> an ugly hack: changing the line
>>
>> sendCommand("call dlopen(\"" + lib + "\", " + flag + ")");
>> to
>> sendCommand("call 'dlopen at plt'(\"" + lib + "\", " + flag + ")");
>>
>> in src/plugins/debugger/gdbengine.cpp makes it work - provided that
>> dlopen has been called at least once from debugged app (for any
>> library) before gdb gets this command. For some reason the PLT proxy
>> does not work correctly if it's called from gdb context to resolve
>> the real function address (which is done first time the proxy is
>> called).
>
> Could you try
>         sendCommand("call (void)dlopen(\"" + lib + "\", " + flag +
> ")");
> like it is done in the Q_OS_MAC part of the code?
>
> Thanks, Eike
>
> --
> Eike Ziller
> Software Engineer
> Nokia, Qt Software
> Phone  +49 (0)30 6392 3255
> Fax    +49 (0)30 6392 3256
> E-mail eike.ziller at nokia.com
>
>
>
>
> _______________________________________________
> Qt-creator mailing list
> Qt-creator at trolltech.com
> http://lists.trolltech.com/mailman/listinfo/qt-creator

-- 
Eike Ziller
Software Engineer
Nokia, Qt Software
Phone  +49 (0)30 6392 3255
Fax    +49 (0)30 6392 3256
E-mail eike.ziller at nokia.com