[2/16][binutils][AARCH64]Add relocation support for large memory model. [LD]Add BFD_RELOC_AARCH64_LD64_GOTOFF_LO15 Support.

[Nick Clifton]

Hi Marcus,

>> +                 /* For local symbol, we have done absolute relocation in
>> static
>> +                    linking stage.  While for share library, we need to
>> update
>> +                    the content of GOT entry according to the share objects
>> +                    loading base address.  So we need to generate a
>> +                    R_AARCH64_RELATIVE reloc for dynamic linker.  */
>> +                 s = globals->root.srelgot;
>> +                 if (s == NULL)
>> +                   abort ();

> This is checking internal consistency, the existing practice both here
> and in _bfd_final_link_relocate which it wraps is to handle internal
> inconsistency with an abort(), so this part of the proposed patch
> seems to me to be consistent with existing practice.

The reason for avoiding calls to abort() inside library functions is 
that the library does not know what the user is trying to do.  For 
example they may be trying out various different ways of linking 
together some object files to find one that works.  A failure to link in 
this case is not a problem for the user - they just go on to try the 
next alternative - but if the library function aborts then they are stuck.

The other problem with calling abort() is that it does not require an 
explanatory message.  Sometime the programmer will have put a helpful 
comment in the code, but not always.  Plus when the user encounters the 
abort they are given no clue as to what is wrong.  They just have to 
report the bug to us and hope that we will fix it.

Still, having said all of that, I do agree that with internal errors, 
sometimes an abort is that best choice.  I would just like to encourage 
contributors to avoid using abort unless there really is no, sensible, 
alternative.

Cheers
   Nick