[PATCH] Update relocation values for ARC platform.

[Nick Clifton]

Hi Ramana,

>> I am worried about this.  What has happened to the old relocation 
>> values (1, 2, 3) ?  What about backwards compatibility ?

> FSF mainline was not ABI compliant with respect to these relocation 
> values. (The relocation values 1, 2 and 3 are actually reserved for the 
> relocation types R_ARC_8, R_ARC_16, R_ARC_24. ostensibly generated by 
> the other toolchain for the ARC cores. ) which the GNU tools does not 
> generate / handle currently.Mainline seems to have the values of 1,2,3 
> for these relocation types since the first revision.
> 
> With respect to backwards compatibility, if anything this should enable 
> users to link in GNU compiled binaries with the other propreitary 
> toolchain with a few more patches that are still in my pipeline. A 
> persistent complaint has been this inability to link object files 
> generated by the 2 toolsets for the ARC platform .

Ok - that is a reasonable reason to break backwards compatibility,

> Would a NEWS item indicating this change  be a valid thing to do 
> indicating that mainline would be broken w.r.t 2.16 branch. ?

Maybe, but see below.

> Or would 
> you want to put in some sort of version checks in the linker based on 
> version info emitted by the assembler ?

Well I think that a nicer solution might be to be put code into 
bfd/elf32-arc.c to handle the "old" style relocation values with a 
warning that support for them will be removed with the next release of 
binutils (ie 2.17).  Obviously you would then have to remember to remove 
this support after the 2.17 branch is cut, whenever that might be.

If this is too long term for you, eg if you are planning to update the 
bfd sources in the near future so that they hand the R_ARC_8, R_ARC_16 
and R_ARC24 relocs, then perhaps a heuristic could be developed to 
distinguish between an object with the old (non ABI compliant) relocs 
and an object file with relocs created by a foreign compiler.  The 
linker could then issue a suitable error message saying that the old 
relocs are no longer supported and that a 2.16 version of the linker is 
needed.

Cheers
   Nick