"Undefined symbols"

"Undefined symbols"

[Xinan Tang]

Hi
    I am using GNU ld version 2.10 (with BF 2.10) and I found out
the FUND' symbols are not reported as error in the link stage.

    For example, the `objdump -t a.out' result looks like:
___________________________________________
00000000  w      *UND*	00000000 L31

____________________________________________

   The label L31 was not defined anywhere in the test program. However,
`ld' did not catch this (I purposely set the label attribute to 'w').

   Could anyone point to me which part of ld source code I should look into?

Thanks


-- 
Dr. Xinan Tang                    Member of Technical Staff
EMail: xinant@cognigine.com       Cognigine Corp.
Voice: 510.743.4930               6120 Stevenson Boulevard
Fax:   510.743.4910               Fremont, CA  94538

Re: "Undefined symbols"

[Nick Clifton]

Hi Dr Xinan,

>     I am using GNU ld version 2.10 (with BF 2.10) and I found out 

2.10 is an old version of GNU ld.  I would first recommend upgrading
to the latest released version (2.11.1) or the latest CVS sources.


> the FUND' symbols are not reported as error in the link stage.
> 
>     For example, the `objdump -t a.out' result looks like:
> ___________________________________________
> 00000000  w      *UND*	00000000 L31
> ____________________________________________
> 
>    The label L31 was not defined anywhere in the test
> program. However, `ld' did not catch this (I purposely set the label
> attribute to 'w').

L31 is a local label, which may be why it is being ignored by the
linker.

You could try adding "--trace-symbol L31" to your linker command line
to see if this helps.

If you can provide a small test case and also tell us which target
configuration you are using then we may be able to reproduce the
problem and offer further insights.

Cheers
        Nick

Re: "Undefined symbols"

[Xinan Tang]

Hi Nick,

Nick Clifton wrote:

> 
> L31 is a local label, which may be why it is being ignored by the
> linker.
> 
> You could try adding "--trace-symbol L31" to your linker command line
> to see if this helps.


   Thanks for your tips.

   I have found the solution. Basically, adding such a piece of code in

   `elf32-target.c' (target is our target name like elf32-mips.c)

________________________________________________________________________

   if (bfd_is_und_section (symbol->section) && (abfd == (bfd *) NULL)) {
         return bfd_reloc_undefined;
    }
    return bfd_reloc_ok;

__________________________________________________________________________

  Therefore, when linker tries to resolve a relocated symbol at last pass,

it will first check whether the symbol is still in the `UND' section.
If that is the case, it will return an undefined error.

Thanks

--Xinan

Re: "Undefined symbols"

[Philip Blundell]

>> ___________________________________________
>> 00000000  w      *UND*	00000000 L31
>> ____________________________________________
>> 
>>    The label L31 was not defined anywhere in the test
>> program. However, `ld' did not catch this (I purposely set the label
>> attribute to 'w').
>
>L31 is a local label, which may be why it is being ignored by the
>linker.

Eh, doesn't "w" signify a weak symbol? 

p.

Re: "Undefined symbols"

[Nick Clifton]

Hi Xinan,

>    Thanks for your tips.
> 
>    I have found the solution. Basically, adding such a piece of code in
> 
>    `elf32-target.c' (target is our target name like elf32-mips.c)
> 
> ________________________________________________________________________
> 
>    if (bfd_is_und_section (symbol->section) && (abfd == (bfd *) NULL)) {
>          return bfd_reloc_undefined;
>     }
>     return bfd_reloc_ok;
> 
> __________________________________________________________________________
> 
>   Therefore, when linker tries to resolve a relocated symbol at last pass,

If you want to submit an official patch we will consider it for
inclusion into the binutils sources.

Cheers
        Nick