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"undefined symbol" when loading dylib compiled on >1.36.0 #67070
Description
undefined symbol: _ZN42_$LT$$RF$T$u20$as$u20$core..fmt..Debug$GT$3fmt17hd0ba07f053fd4c7fE
My project structure:
parent
main.rs # binary, loads libchild.so via libloading
lib.rs # dylib, shared code
child
lib.rs # dylib, dynamically linked to libparent.so
This compiles fine, but fails to load libchild.so when compiled on anything newer than 1.36.0. If the parent library is made non-dylib, it works fine, however this is not a viable solution for my project as it causes libchild.so to contain all the shared code, and my project has many libchild.so-equivalent crates.
Demo case: https://github.com/GinjaNinja32/rust-issues/tree/undefined-symbol-core-fmt-debug (has 70 dependency crates, mostly indirect; I'm not sure exactly where it goes wrong or how to make it smaller)
Bisected to merge dbebcee, #59752.
rustc 1.39.0 (4560ea788 2019-11-04)
binary: rustc
commit-hash: 4560ea788cb760f0a34127156c78e2552949f734
commit-date: 2019-11-04
host: x86_64-unknown-linux-gnu
release: 1.39.0
LLVM version: 9.0
Activity
GinjaNinja32 commentedon Dec 5, 2019
...and now my test project does the same thing on 1.36.0.
My real project works fine on 1.36.0, so maybe my test project just has a different bug that happens to give the same error? I have no idea what's going on with this.
The bisection results were with my real project, though, so those should be accurate for the issue I'm actually seeing there.
jonas-schievink commentedon Dec 5, 2019
Caused by #59752
nagisa commentedon Dec 8, 2019
Possible duplicate of #65610.
The linked issue as the fix you can make to the code to make this work again (you need theMy bad, this project does not involve extern blocks.#[link]annotations on yourexternblocks)GinjaNinja32 commentedon Feb 20, 2020
Rust 1.42 seems to fix this for my real project; the test project I linked above remains broken even on nightly 2020-02-19.
My real project now doesn't even build on 1.37-1.41 (see #69328), but it builds and runs fine on both 1.36 and 1.42.