Re: PATCH: Share the dwarf2 unwind code between glibc and gcc 3.0

["H . J . Lu" <hjl at lucon dot org>]

On Mon, Jul 09, 2001 at 10:10:10AM -0700, Geoff Keating wrote:
> > > I don't understand what you mean by "share the dwarf2 unwind code".
> > > There should be only one copy on a system at a time.  Either that copy
> > > is from GCC or from glibc, but if there is only one of it, the copy
> > > cannot come from two places.  
> > 
> > Exactly. They have to be the same in functionality. By `shaere', I
> > meant the same code can be used in both gcc and glibc so that we are
> > sure either copy will do the job right.
> 
> Only one copy can be used.  Which copy should it be?  Or do you intend

It depends on how a DSO is built and by which vesion of gcc. The
key is only one copy can be used at the run time. The copies in libgcc
and glibc have to work the same.

> that the last one installed wins?  Have you tested this?

Yes. It is kind of tricky to set it up.

> > What do you mean by that? My patch shouldn't change anything in gcc.
> > It just makes it possible to compile the same gcc code in glibc.
> 
> I mean, I don't understand how you think this should work, and I want
> to see documentation.

It is no major difference from the glibc compiled with gcc pre 3.0. I
assume you do know that there is a frame unwinder in libc.so. The only
difference my patch makes is the new frame unwinder in libc.so supports
both the gcc v2 and v3 frames. We achieve that by putting the gcc v3
frame unwinder in glibc plus the the frame unwinder from gcc 2.9x.

> Not just the ABI, although that is certainly necessary, but an
> interface document that says which parts glibc is responsible for, and
> which parts are from GCC, and how the parts interact, and which parts
> change, and which parts don't change, and which parts get tested, and
> what does the testing, and how the parts get updated, and how system
> integrators package them, and so on.
> 

Good idea. Where should I put it?

> > Can we have it now since we are on it?
> 
> Yes.  If you write some documentation, I will review it.

I don't have the time to write the libgcc ABI documentation.


H.J.