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Re: RFC: Patch to fix MIPS -mno-shared with multi-got...


On Thu, Mar 03, 2005 at 03:57:04PM -0800, David Daney wrote:
> Thiemo Seufer wrote:
> >David Daney wrote:
> >[snip]
> >
> >>>WRT possible breakge to things expecting the real "_gp": I agree that
> >>>might be a problem.  One possibility would be to define a new symbol,
> >>>something like __gnu_local_gp, and make -mno-shared use that instead
> >>>of plain _gp.  -mno-shared is a new option, so there's no backwards
> >>>compatiblity problem.
> >>
> >>OK, I kind of like this idea.  But I am not an ABI authority.  I am 
> >>assuming the the meaning of "_gp_disp" is defined somewhere in the ABI 
> >>specs.  I know _gp is specified.  Does anybody have objections to adding 
> >>the new magic __gnu_local_gp symbol?
> >
> >
> >I have the general (and still vague) idea to have multigot-capable object
> >files, with _gp _gp.1 .. _gp.n and _gp_disp _gp_disp.1 .. _gp_disp.n
> >depending on the GOT in use, and with the single got case staying binary
> >compatible. I think this would cover your case as well, but it's of
> >course much more work.

As David said, I think this solves a different problem.

> Yes, it makes my head hurt just to think about it.
> 
> In lieu of doing that I present the attached patch.
> 
> The main question being:  Use _gp or __gnu_local_gp ?
> 
> The pros of using _gp are that Thiemo's plan to magically rename _gp 
> would be binary compatible.
> 
> The pros of using __gnu_local_gp are that existing code using _gp 
> outside of .cpload would continue to work.
> 
> I am inclined to use _gp as it does not create a gnu specific ABI 
> extension, but I am apprehensive about what will happen when I try to 
> build glibc.

We can handle __gnu_local_gp.1 just as easily as _gp.1, once someone
does the work :-)  I don't have much of a preference.

-- 
Daniel Jacobowitz
CodeSourcery, LLC


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