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Re: gcc-cross-dev details and future plans

+++ Helmut Grohne [2014-12-18 12:49 +0100]:
> On Thu, Dec 18, 2014 at 11:16:34AM +0000, Wookey wrote:
> > re gcc-source versioning:
> > Dima5: We could also make cross-gcc-dev contain the actual patched gcc
> >        source. that would still make its installation set the same size as
> >        when it depends on gcc-4.9-source, but it would always be installable
> This seems to be wrongly attributed. I said this.

> When I suggested this, it was just a thought exercise furthering the
> idea of cross-gcc-dev Depending on gcc-4.9-source. (I'm not yet
> convinced that this is indeed necessary.)

As you say, 'just an idea'. 
> > So, yes a given gcc is only guaranteed to work with the matching
> > version of libgcc1 (According to toolchain engineers, I checked), so
> > the dependency really should be '='. We changed this in the
> > cross-toolchains. Now in practice it usually will work with some
> > nearby versions, so we could be more flexible, but '=' is safe.
> Given the situation in sid, something seems wrong here. gcc-4.8 Depends
> on libgcc-4.8-dev (>= ...) which Depends on libgcc1 (>= ...). But the
> libgcc1 it actually ends up with is the one from gcc-4.9. Cleary,
> gcc-4.8 (as packaged in Debian) is not using a nearby libgcc1 version.
> So either that toolchain engineer you are referring to is wrong or the
> gcc-4.8 package in Debian is quite broken.

Yes. I agree that doesn't seem to make much sense. I asked Marcus
Shawcroft (aarch64 gcc lead) who generally knows what he's talking
about. libgcc1 contains various useful runtime subroutines. I don't
know what guarantees gcc makes about the interface to libgcc1
remaining consistent across versions. 

I did ask for clarification in 770413, but didn't get any. 

Doko, what are the restrictions on gcc/libgcc matching? Is >= in fact
correct, even across different gcc minor versions (4.8/4.9 etc) and we
can assume forwards compatibility?

Principal hats:  Linaro, Debian, Wookware, ARM

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