MIPS, libsupc++ and -G 0

[Jonathan Larmour]

Richard Sandiford wrote:
> Zack Weinberg <zack@codesourcery.com> writes:
> 
>>Richard Sandiford <rsandifo@redhat.com> writes:
>>
>>>The only reliable way to get what you want is to either (a) add -G0
>>>multilibs or (b) change the default -G setting.  Perhaps a configure
>>>option would be useful here.  Maybe something like --with-sdata-limit,
>>>to go alongside options like --with-arch and --with-tune?
>>
>>Or perhaps an -m option to put stuff in .sdata as normal, but generate
>>code as if nothing is in there?
> 
> 
> Maybe (and I realise other ports do) but in some ways it gives the worst
> of both worlds.  libsupc++ and libstdc++ will end up eating chunks of the
> small data area without getting any real benefit from it.
> 
> A configure-time option is likely to be more convenient for folks who
> use -G0 because you don't have to coerce every build system to add it
> on the command line.  And it wouldn't penalise those who want to use
> the usual -G8.

Unfortunately the decision to use or not use -G 0 isn't taken on a 
per-compiler basis usually, but a per-application one. A -G 0 multilib 
doesn't seem good either because someone may have an application that 
doesn't link with -G 8, but might with -G 4, and at least get some benefit 
from small data. Or arguably -G 2.

I think for what is in effect a system library, Zack's proposal seems least 
bad, even though it has drawbacks. And potentially no drawbacks if someone 
ever implements linker relaxation for MIPS.

Jifl