[gentoo-dev] libffi-3.4 is on the horison (unkeyworded for now, ~arch soon)

[gentoo-dev] libffi-3.4 is on the horison (unkeyworded for now, ~arch soon)

[Sergei Trofimovich]

Tl;DR
-----

  libffi-3.4 entered ::gento without KEYWORDS today.
  After some testing it will be promoted into ~arch.

  libffi has two modes:
  1. USE=-exec-static-trampoline: old (default, safe)
  2. USE=exec-static-trampoline: new (cool, might expose latent bugs)

  +toralf@ (CC):
    Toralf, can we set a tinderbox run for [1.]
      >=dev-libs/libffi-3.4[-exec-static-trampoline]
    case?

    [2.] would also be nice:
      >=dev-libs/libffi-3.4[exec-static-trampoline]
    My worry is that it will generate a lot of collateral
    breakage (at least some percentage of dev-haskell/*).

  Tracker: https://bugs.gentoo.org/801109
  Known examples: https://wiki.gentoo.org/index.php?title=Project:Toolchain#libffi-3.4

More help
---------

If you happen to maintain a Gentoo package that uses libffi
you can try libffi-3.4 early to see how it behaves.

- Try [1.] on packages you maintain.
- If you are brave try [2.] as well but be ready to recover
  your system! A few packages are already known to be affected:
    https://wiki.gentoo.org/index.php?title=Project:Toolchain#libffi-3.4

Add new bugs you found as blockers to the libffi-3.4 tracker:
    https://bugs.gentoo.org/801109

More words
----------

In this release most probably impactful change is a trampoline
code handling change.

Before 3.4 libffi generated all code at runtime in a single
executable chunk of executable memory.

Since 3.4 libffi uses does not use runtime code generation and
uses statically defined trampoline in a very clever way:
    https://sourceware.org/pipermail/libffi-discuss/2021/002579.html

This should not be a problem for most applications, but two
are already known to fail:

- ghc: https://gitlab.haskell.org/ghc/ghc/-/issues/20051
- gobject-introspection: https://gitlab.gnome.org/GNOME/gobject-introspection/-/merge_requests/283

The symptoms are SIGSEGVs and erratic behaviour.

To workaround widespread breakage libffi-3.4 provides a fallback mode
that reuses libffi-3.3 style trampoline layout via USE=-exec-static-trampoline.

Also note that libffi-3.4 also changes SONAME from libffi.so.7
to libffi.so.8. It will rebuild a few packages as a result.
It's a good time to check for missing rebuild slot operator in
depends.

If you broke your system with USE=exec-static-trampoline try to
recover with USE=-exec-static-trampoline first. It should avoid
rebuilding revdeps back to .so.7.

Debugging help
--------------

If you suspect your package is affected then CC toolchain@
to the relevant bug and we'll try to sort it out together.

Have fun!

-- 

  Sergei

[gentoo-dev] Re: libffi-3.4 is on the horison (unkeyworded for now, ~arch soon)

[Toralf Förster]

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On 7/8/21 1:20 AM, Sergei Trofimovich wrote:
> Tl;DR
> -----
> 
>    libffi-3.4 entered ::gento without KEYWORDS today.
>    After some testing it will be promoted into ~arch.
> 
>    libffi has two modes:
>    1. USE=-exec-static-trampoline: old (default, safe)
>    2. USE=exec-static-trampoline: new (cool, might expose latent bugs)
> 
>    +toralf@ (CC):
>      Toralf, can we set a tinderbox run for [1.]
>        >=dev-libs/libffi-3.4[-exec-static-trampoline]
>      case?
> 
>      [2.] would also be nice:
>        >=dev-libs/libffi-3.4[exec-static-trampoline]
>      My worry is that it will generate a lot of collateral
>      breakage (at least some percentage of dev-haskell/*).
> 
>    Tracker: https://bugs.gentoo.org/801109
>    Known examples: https://wiki.gentoo.org/index.php?title=Project:Toolchain#libffi-3.4

will do

> Have fun!
> 
sure

-- 
Toralf
PGP 23217DA7 9B888F45


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Re: [gentoo-dev] libffi-3.4 is on the horison (unkeyworded for now, ~arch soon)

[Sergei Trofimovich]

On Thu, 8 Jul 2021 00:20:58 +0100
Sergei Trofimovich <slyfox@gentoo.org> wrote:

> Tl;DR
> -----
> 
>   libffi-3.4 entered ::gento without KEYWORDS today.
>   After some testing it will be promoted into ~arch.
> 
>   libffi has two modes:
>   1. USE=-exec-static-trampoline: old (default, safe)
>   2. USE=exec-static-trampoline: new (cool, might expose latent bugs)

Default USE=-exec-static-trampoline did not expose any new
failures over past week.

If next week will be as calm we can unleash libffi into
~arch next weekend (~24 July 2021).

-- 

  Sergei

Re: [gentoo-dev] libffi-3.4 is on the horison (unkeyworded for now, ~arch soon)

[Sergei Trofimovich]

On Sat, 17 Jul 2021 20:14:52 +0100
Sergei Trofimovich <slyfox@gentoo.org> wrote:

> On Thu, 8 Jul 2021 00:20:58 +0100
> Sergei Trofimovich <slyfox@gentoo.org> wrote:
> 
> > Tl;DR
> > -----
> > 
> >   libffi-3.4 entered ::gento without KEYWORDS today.
> >   After some testing it will be promoted into ~arch.
> > 
> >   libffi has two modes:
> >   1. USE=-exec-static-trampoline: old (default, safe)
> >   2. USE=exec-static-trampoline: new (cool, might expose latent bugs)  
> 
> Default USE=-exec-static-trampoline did not expose any new
> failures over past week.
> 
> If next week will be as calm we can unleash libffi into
> ~arch next weekend (~24 July 2021).

libffi-3.4.2 pushed to ~arch as:
    https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=e03b5b8d5f1a5023dff4c341bb40578690471acb

-- 

  Sergei