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Re: [PATCH] Bump LTO_major_version
On Mon, 29 Nov 2010, Jan Hubicka wrote:
> >
> > This bumps the LTO major version and makes us reject LTO objects built
> > with 4.5 instead of crash in the option handling code.
>
> Uh, thanks for looking into this!
> >
> > I tried to look at incorporating some checksum like we do for PCH, but
> > the mechanism can't be easily re-used and I'm somewhat lost how to
> > tackle the Makefile dependency issues given that LTO isn't always
> > enabled (I thought of doing a lto1-checksum.c similar to the cc1
> > and cc1plus ones and just re-use the same checksum in all frontends -
> > which makes their link depend on lto1-checksum.c, conditionally).
>
> Perhaps we can take the route of Andi's patch that checksums objects rather
> than binaries (he did that to speedup bootstrap-lto). Then we can checksum
> libbackend objects only.
It just also occured to me that I would have disliked having the
(for example lto1) checksum as part of the object - that way tracking
down SPEC 2k6 link-time bugs by patching around in the source would
have been very very annoying ...
So I guess we really don't want _this_ strict testing ...
Thus, let's not care for trunk builds and try to make sure we don't
break compatibility too much on a branch (or remember to bump
the LTO minor version).
Richard.