[GSOC2013] Dynamic object file loading

[Peng Fan]

It works when I add a 'int rtems(int argc, char **argv)' function. Thanks.


2013/4/20 Chris Johns <chrisj at rtems.org>

> Peng Fan wrote:
>
>>
>>     Added the code, I can see the three files: libx.a shell-init  x.rap
>>
>>     Here appears another problem:
>>
>>     When"rap ld ./x.rap", it tells"error: loading: (0)"
>>
>>     When"dlo x.rap","error: duplicate global symbol: hello". However,
>>  dlo libx.a:xa.c.1.o and dlo libx.a:x-long-name-to-create-**gnu-extension-in-archive.c.1.o
>> is ok.
>>
>>
>> Tried to find why "When "rap ld ./x.rap", it tells "error: loading: (0)""
>>
>
> Did you grep for the string and set a break point in it and then look at
> the back trace ? This is a pretty bad error message. Something is wrong
> here.
>
>
>  I trace rtld using sparc-rtems4.11-gdb.
>> In rap.c, there are two functions to do the loading ,linking and finding
>> symbol job, dlopen foucsing on loading and resolving symbols, while
>> dlsym returns the symbol address.
>>
>
> Correct.
>
>  When debugging dlopen returns sucessfully, but "init = dlsym
>> (app->handle, "*rtems*");" returns with "init=NULL".Thus rap load failed.
>>
>
> What is "*rtems*" ? Wild cards will not work.
>
>
>  In dlsym, It first try find the symbol in it's local "global_table".
>>
>
> Correct.
>
>  In
>> x.rap, It's global_table includes "hello", "w_writeln" ,"x_writeln",
>> "y_writeln", "z_writeln", "public", "my_main". with no one matches
>> "*rtems*". Then It tries to find the symbol in global symbol which maybe
>>
>> generated in rtld-gsyms.c using a hash method.However, it still can not
>> find the    match "rtems" symbol. Thus, failed.
>>
>
> Oh ok I get what is happening, yes this is correct. The symbols is 'rtems'
> and it is a kind of 'main' for the RTEMS application. It is nothing more
> than that. The x.rap is a progression and I ended up testing the whole
> think with a waf based libbsdports that create a RAP image. I need to get
> this out onto a server somewhere.
>
>
>
>> I do not know the "rtems" symbol means what. I see it is assigned to
>> init, and then init(*, *). I am confusing  about why "rtems".
>>
>>
> This is understandable because I failed to add the reason to the doco. As
> I said this is an RTEMS Application's main. I did not want to use main
> because this has a well known and understood use.
>
> Well done on getting this far. If you add an 'rtems' function to the x.rap
> and have it print something the load should work.
>
> Chris
>
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