Dynamic Libraries

[Joel Sherrill]

Marek Prochazka wrote:
> Please, anyone having a hint how to deal with the problem described
> below? Or should I consider the issue being hard to solve in an easy way
> and hence Cexp not being able to use on sparc-rtems? Sorry but I have to
> keep pushing as I have to decide reasonably quickly whether I can use
> Cexp for my project or not.
>
>   
AFAIK this is an ld issue not specifically Cexp.  I saw this message about
this error message on an  old thread on the binutils list (typed in so I 
hope
the URL is right):

http://sourceware.org/ml/binutils/2003-04/msg00540.html

Maybe you can tell from that discussion what is going on with this linker
script.  I don't think this is as much SPARC specific as an odd side-effect
of your test case and linker script.

--joel
> Thanks.
>
> Best regards,
> Marek Prochazka
>
>   
>> -----Original Message-----
>> From: Marek Prochazka [mailto:Marek.Prochazka at scisys.co.uk] 
>> Sent: 12 September 2006 17:18
>> To: Till Straumann
>> Cc: rtems-users at rtems.com
>> Subject: RE: Dynamic Libraries
>>
>> Hi,
>>
>> I have successfully linked a Cexp "loader" application on 
>> Linux and was
>> able to load modules at runtime. Quite good stuff!
>>
>> When I am trying to do the same for sparc-rtems target, I get the
>> following message when linking:
>>
>> /opt/rtems-4.6/lib/gcc-lib/sparc-rtems/3.2.3/../../../../sparc
>> -rtems/bin
>> /ld: ADDR forward reference of section .text
>>
>> My link_helper file looks like this:
>>
>> __cexp__dummy_alias_0 = ADDR( .text ) ;
>> __cexp__dummy_alias_1 = ADDR( .data ) ;
>> __cexp__dummy_alias_2 = ADDR( .bss ) ;
>> __cexp__dummy_alias_3 = ADDR( .jcr ) ;
>>
>> Corresponding part of mysymbtab.c is
>>
>> static CexpSymRec systemSymbols[] = {
>> 	{
>> 		.name       =".text",
>> 		.value.ptv  =(void*)&__cexp__dummy_alias_0,
>> 		.value.type =TVoid,
>> 		.size       =0,
>> 		.flags      =0|CEXP_SYMFLG_SECT,
>> 	},
>> 	{
>> 		.name       =".data",
>> 		.value.ptv  =(void*)&__cexp__dummy_alias_1,
>> 		.value.type =TVoid,
>> 		.size       =0,
>> 		.flags      =0|CEXP_SYMFLG_SECT,
>> 	},
>> 	{
>> 		.name       =".bss",
>> 		.value.ptv  =(void*)&__cexp__dummy_alias_2,
>> 		.value.type =TVoid,
>> 		.size       =0,
>> 		.flags      =0|CEXP_SYMFLG_SECT,
>> 	},
>> 	{
>> 		.name       =".jcr",
>> 		.value.ptv  =(void*)&__cexp__dummy_alias_3,
>> 		.value.type =TVoid,
>> 		.size       =0,
>> 		.flags      =0|CEXP_SYMFLG_SECT,
>> 	},
>> 	...
>>
>> I have built libcexp for sparc-rtems and xsyms on Linux for 
>> sparc-rtems
>> target. When I tried to build xsyms on top of libelf (--disable-bfd
>> --disable-cexp) then the mysymtab.c file generated by xsyms 
>> is actually
>> a binary file - so I do not know how use it.
>>
>> Any hints related to this?
>>
>> Many thanks,
>> Marek
>>
>>
>>     
>>> -----Original Message-----
>>> From: Marek Prochazka [mailto:Marek.Prochazka at scisys.co.uk] 
>>> Sent: 12 September 2006 09:28
>>> To: Till Straumann
>>> Cc: rtems-users at rtems.com
>>> Subject: RE: Dynamic Libraries
>>>
>>> Hi,
>>>
>>> thanks, this helped me to link it! BTW my version of the 
>>>       
>> README file,
>>     
>>> which comes from Cexp 1.5 sources downloaded from the Cexp 
>>>       
>> home page,
>>     
>>> does not mention the trick with "> link_helper" in points 2) and 4).
>>>
>>> Regards,
>>> Marek
>>>
>>>       
>>>> Allan is correct. RTMF (see step 4), please [from the README]:
>>>>
>>>>  >  1) compile and link all sources, libraries etc.; build an 
>>>> executable
>>>>  >  2) xsyms -C executable  mysymtab.c > link_helper
>>>>  >  3) compile mysymtab.c (set -I to Cexp source directory, since
>>>>  >     cexpsyms.h is included)
>>>>  >  4) link application again, but this time add 
>>>>         
>> 'mysymtab.c' to the
>>     
>>>>  >     list of sources and 'link_helper' to the list of files to
>>>>  >     be linked.
>>>>  >  NOTE: Step 1) linking succeeds without a symtab.o 
>>>>         
>>> because there's
>>>       
>>>>  >        a weak NULL-ptr alias for the builtin symtab.
>>>>
>>>> HTH
>>>> -- Till
>>>>
>>>>         
>>>       
>>     
>
>