[Pkg-d-devel] Installing libphobos2-ldc75

[Matthias Klumpp]

Hi!

2017-11-08 9:08 GMT+01:00 Russel Winder <russel at winder.org.uk>:
> Hi,
>
> I see that libphobos2-ldc75 states it has a conflict with libphobos2-
> ldc74 but this seems against the philosophy of Debian that allows for
> many versions of libraries.
>
> In this case the update is blocked because tilix depends on libphobos2-
> ldc74 and so libphobos2-ldc75 fails to install blocking the
> installation of ldc 1.5.0.
>
> If both libphobos2-ldc74 and libphobos2-ldc75 could both be installed,
> the compiler upgrade would not block.

This is intentional, check the LDC changelog.
While usually it is very discouraged to have library packages conflict
(and most of the time a sign that you are doing something wrong), in
this case it is justified because we want to ensure that the current
LDC transition does not break the user's systems or unrelated
packages.
In the past it happened often that some packages up in the dependency
chain (e.g. gtk-d) were compiled with newer versions of LDC, and some
packages lower in the chain were still on the old version (e.g. tilix)
which caused them to just break without notice for users who had
updated their system. This was made worse by LLVM and LDC bugs which
got packages stuck in this state for quite a long time.

By making the new Phobos library conflict with the old one, we ensure
users do only update to the new LDC runtime packages when nothing on
their system uses the old ones anymore, effectively ensuring we don't
break anything for them with the transition.
This is far from ideal (ideally D would have a stable ABI...), but
IMHO it's better than the previous state.

At the moment this is an experiment, if we find serious issue with it
we'll have to think of something else to fix this issue (but at the
moment it's working as expected).
Just wait for all the stuff to be rebuilt with the new LDC, and then
you should be able to easily update to the new version.

Cheers,
    Matthias


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