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Tl;DR |
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----- |
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|
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libffi-3.4 entered ::gento without KEYWORDS today. |
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After some testing it will be promoted into ~arch. |
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|
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libffi has two modes: |
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1. USE=-exec-static-trampoline: old (default, safe) |
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2. USE=exec-static-trampoline: new (cool, might expose latent bugs) |
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|
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+toralf@ (CC): |
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Toralf, can we set a tinderbox run for [1.] |
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>=dev-libs/libffi-3.4[-exec-static-trampoline] |
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case? |
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|
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[2.] would also be nice: |
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>=dev-libs/libffi-3.4[exec-static-trampoline] |
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My worry is that it will generate a lot of collateral |
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breakage (at least some percentage of dev-haskell/*). |
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|
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Tracker: https://bugs.gentoo.org/801109 |
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Known examples: https://wiki.gentoo.org/index.php?title=Project:Toolchain#libffi-3.4 |
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|
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More help |
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--------- |
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|
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If you happen to maintain a Gentoo package that uses libffi |
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you can try libffi-3.4 early to see how it behaves. |
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|
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- Try [1.] on packages you maintain. |
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- If you are brave try [2.] as well but be ready to recover |
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your system! A few packages are already known to be affected: |
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https://wiki.gentoo.org/index.php?title=Project:Toolchain#libffi-3.4 |
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|
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Add new bugs you found as blockers to the libffi-3.4 tracker: |
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https://bugs.gentoo.org/801109 |
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|
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More words |
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---------- |
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|
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In this release most probably impactful change is a trampoline |
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code handling change. |
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|
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Before 3.4 libffi generated all code at runtime in a single |
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executable chunk of executable memory. |
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|
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Since 3.4 libffi uses does not use runtime code generation and |
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uses statically defined trampoline in a very clever way: |
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https://sourceware.org/pipermail/libffi-discuss/2021/002579.html |
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|
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This should not be a problem for most applications, but two |
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are already known to fail: |
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|
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- ghc: https://gitlab.haskell.org/ghc/ghc/-/issues/20051 |
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- gobject-introspection: https://gitlab.gnome.org/GNOME/gobject-introspection/-/merge_requests/283 |
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|
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The symptoms are SIGSEGVs and erratic behaviour. |
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|
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To workaround widespread breakage libffi-3.4 provides a fallback mode |
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that reuses libffi-3.3 style trampoline layout via USE=-exec-static-trampoline. |
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|
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Also note that libffi-3.4 also changes SONAME from libffi.so.7 |
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to libffi.so.8. It will rebuild a few packages as a result. |
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It's a good time to check for missing rebuild slot operator in |
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depends. |
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|
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If you broke your system with USE=exec-static-trampoline try to |
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recover with USE=-exec-static-trampoline first. It should avoid |
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rebuilding revdeps back to .so.7. |
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|
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Debugging help |
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-------------- |
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|
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If you suspect your package is affected then CC toolchain@ |
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to the relevant bug and we'll try to sort it out together. |
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|
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Have fun! |
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|
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-- |
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|
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Sergei |
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