linker-plugin-lto stopped working in Rust 1.45.0

[heftig]

After upgrading from Rust 1.44.1 to Rust 1.45.0, Firefox's LTO build failed to link a crate build script with undefined reference to '__rust_probestack'.

The system is Arch Linux, which has binutils 2.34, GCC 10.1.0, LLVM 10.0.0, Clang 10.0.0.

Originally posted at https://bugzilla.mozilla.org/show_bug.cgi?id=1640982#c30:

I can replicate the error with rustup and the rusqlite crate (https://github.com/rusqlite/rusqlite) like this:

rusqlite> CARGO_PROFILE_RELEASE_LTO=true RUSTFLAGS="-Clinker-plugin-lto=LLVMgold.so" cargo +stable build --release                
    Updating crates.io index
   Compiling pkg-config v0.3.18
   Compiling libc v0.2.73
   Compiling bitflags v1.2.1
   Compiling memchr v2.3.3
   Compiling linked-hash-map v0.5.3
   Compiling fallible-streaming-iterator v0.1.9
   Compiling smallvec v1.4.1
   Compiling fallible-iterator v0.2.0
   Compiling lru-cache v0.1.2
   Compiling libsqlite3-sys v0.19.0 (/home/jan/vc/rusqlite/libsqlite3-sys)
   Compiling time v0.1.43
error: linking with `cc` failed: exit code: 1
  |
  = note: "cc" "-Wl,--as-needed" "-Wl,-z,noexecstack" "-m64" "-Wl,-plugin=LLVMgold.so" "-Wl,-plugin-opt=O3" "-Wl,-plugin-opt=mcpu=x86-64" "-L" "/home/jan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib" "/home/jan/vc/rusqlite/target/release/build/libsqlite3-sys-f447ce3cb2731b7a/build_script_build-f447ce3cb2731b7a.build_script_build.7mwl8gcz-cgu.0.rcgu.o" "/home/jan/vc/rusqlite/target/release/build/libsqlite3-sys-f447ce3cb2731b7a/build_script_build-f447ce3cb2731b7a.build_script_build.7mwl8gcz-cgu.1.rcgu.o" "/home/jan/vc/rusqlite/target/release/build/libsqlite3-sys-f447ce3cb2731b7a/build_script_build-f447ce3cb2731b7a.build_script_build.7mwl8gcz-cgu.10.rcgu.o" "/home/jan/vc/rusqlite/target/release/build/libsqlite3-sys-f447ce3cb2731b7a/build_script_build-f447ce3cb2731b7a.build_script_build.7mwl8gcz-cgu.11.rcgu.o" "/home/jan/vc/rusqlite/target/release/build/libsqlite3-sys-f447ce3cb2731b7a/build_script_build-f447ce3cb2731b7a.build_script_build.7mwl8gcz-cgu.12.rcgu.o" "/home/jan/vc/rusqlite/target/release/build/libsqlite3-sys-f447ce3cb2731b7a/build_script_build-f447ce3cb2731b7a.build_script_build.7mwl8gcz-cgu.13.rcgu.o" "/home/jan/vc/rusqlite/target/release/build/libsqlite3-sys-f447ce3cb2731b7a/build_script_build-f447ce3cb2731b7a.build_script_build.7mwl8gcz-cgu.14.rcgu.o" "/home/jan/vc/rusqlite/target/release/build/libsqlite3-sys-f447ce3cb2731b7a/build_script_build-f447ce3cb2731b7a.build_script_build.7mwl8gcz-cgu.15.rcgu.o" "/home/jan/vc/rusqlite/target/release/build/libsqlite3-sys-f447ce3cb2731b7a/build_script_build-f447ce3cb2731b7a.build_script_build.7mwl8gcz-cgu.2.rcgu.o" "/home/jan/vc/rusqlite/target/release/build/libsqlite3-sys-f447ce3cb2731b7a/build_script_build-f447ce3cb2731b7a.build_script_build.7mwl8gcz-cgu.3.rcgu.o" "/home/jan/vc/rusqlite/target/release/build/libsqlite3-sys-f447ce3cb2731b7a/build_script_build-f447ce3cb2731b7a.build_script_build.7mwl8gcz-cgu.4.rcgu.o" "/home/jan/vc/rusqlite/target/release/build/libsqlite3-sys-f447ce3cb2731b7a/build_script_build-f447ce3cb2731b7a.build_script_build.7mwl8gcz-cgu.5.rcgu.o" "/home/jan/vc/rusqlite/target/release/build/libsqlite3-sys-f447ce3cb2731b7a/build_script_build-f447ce3cb2731b7a.build_script_build.7mwl8gcz-cgu.6.rcgu.o" "/home/jan/vc/rusqlite/target/release/build/libsqlite3-sys-f447ce3cb2731b7a/build_script_build-f447ce3cb2731b7a.build_script_build.7mwl8gcz-cgu.7.rcgu.o" "/home/jan/vc/rusqlite/target/release/build/libsqlite3-sys-f447ce3cb2731b7a/build_script_build-f447ce3cb2731b7a.build_script_build.7mwl8gcz-cgu.8.rcgu.o" "/home/jan/vc/rusqlite/target/release/build/libsqlite3-sys-f447ce3cb2731b7a/build_script_build-f447ce3cb2731b7a.build_script_build.7mwl8gcz-cgu.9.rcgu.o" "-o" "/home/jan/vc/rusqlite/target/release/build/libsqlite3-sys-f447ce3cb2731b7a/build_script_build-f447ce3cb2731b7a" "/home/jan/vc/rusqlite/target/release/build/libsqlite3-sys-f447ce3cb2731b7a/build_script_build-f447ce3cb2731b7a.497gn0w79xbcp3uz.rcgu.o" "-Wl,--gc-sections" "-pie" "-Wl,-zrelro" "-Wl,-znow" "-Wl,-O1" "-nodefaultlibs" "-L" "/home/jan/vc/rusqlite/target/release/deps" "-L" "/home/jan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-Wl,-Bstatic" "/home/jan/vc/rusqlite/target/release/deps/libpkg_config-800dea52ae78bc9e.rlib" "-Wl,--start-group" "/home/jan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libstd-c147cd9c030850ef.rlib" "/home/jan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libpanic_unwind-7e62a3a07bb85bc1.rlib" "/home/jan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libhashbrown-000f77165d4d2d36.rlib" "/home/jan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_std_workspace_alloc-7dc0cb59ed386ac6.rlib" "/home/jan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libbacktrace-9248bfbd7273ac3d.rlib" "/home/jan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libbacktrace_sys-b75363fb938de39d.rlib" "/home/jan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_demangle-7bbe96f555da4ad6.rlib" "/home/jan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libunwind-a145493c64eeb044.rlib" "/home/jan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcfg_if-9577436fc6fce6bc.rlib" "/home/jan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/liblibc-b3376c0a2b35415c.rlib" "/home/jan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/liballoc-5708f6b2b59b6e0f.rlib" "/home/jan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_std_workspace_core-e9fd09201d99d6f4.rlib" "/home/jan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcore-914c6ef6f5cf354a.rlib" "-Wl,--end-group" "/home/jan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcompiler_builtins-1445b6c7903692a2.rlib" "-Wl,-Bdynamic" "-ldl" "-lrt" "-lpthread" "-lgcc_s" "-lc" "-lm" "-lrt" "-lpthread" "-lutil" "-ldl" "-lutil"
  = note: /usr/bin/ld: /tmp/lto-llvm-7519f5.o: in function `std::sys::unix::fs::copy':
          /rustc/5c1f21c3b82297671ad3ae1e8c942d2ca92e84f2//src/libstd/sys/unix/fs.rs:1172: undefined reference to `__rust_probestack'
          collect2: error: ld returned 1 exit status
          

error: aborting due to previous error

error: could not compile `libsqlite3-sys`.

To learn more, run the command again with --verbose.
warning: build failed, waiting for other jobs to finish...
error: build failed

This works with 1.44.1:

rusqlite> CARGO_PROFILE_RELEASE_LTO=true RUSTFLAGS="-Clinker-plugin-lto=LLVMgold.so" cargo +1.44.1 build --release
   Compiling libc v0.2.73
   Compiling pkg-config v0.3.18
   Compiling memchr v2.3.3
   Compiling bitflags v1.2.1
   Compiling linked-hash-map v0.5.3
   Compiling smallvec v1.4.1
   Compiling fallible-streaming-iterator v0.1.9
   Compiling fallible-iterator v0.2.0
   Compiling lru-cache v0.1.2
   Compiling libsqlite3-sys v0.19.0 (/home/jan/vc/rusqlite/libsqlite3-sys)
   Compiling time v0.1.43
   Compiling rusqlite v0.23.1 (/home/jan/vc/rusqlite)
    Finished release [optimized] target(s) in 3.56s

---

Using clang -flto as the linker instead of GCC with explicit LLVMgold.so behaves analogously:

fails:    CARGO_PROFILE_RELEASE_LTO=true CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang RUSTFLAGS="-Clinker-plugin-lto -Clink-arg=-flto" cargo +stable build --release
succeeds: CARGO_PROFILE_RELEASE_LTO=true CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang RUSTFLAGS="-Clinker-plugin-lto -Clink-arg=-flto" cargo +1.44.1 build --release

Using LLD or gold instead of the BFD linker also makes it work:

CARGO_PROFILE_RELEASE_LTO=true RUSTFLAGS="-Clinker-plugin-lto=LLVMgold.so -Clink-arg=-fuse-ld=gold" cargo +stable build --release
CARGO_PROFILE_RELEASE_LTO=true RUSTFLAGS="-Clinker-plugin-lto=LLVMgold.so -Clink-arg=-fuse-ld=lld" cargo +stable build --release
CARGO_PROFILE_RELEASE_LTO=true CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang RUSTFLAGS="-Clinker-plugin-lto -Clink-arg=-flto -Clink-arg=-fuse-ld=gold" cargo +stable build --release
CARGO_PROFILE_RELEASE_LTO=true CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang RUSTFLAGS="-Clinker-plugin-lto -Clink-arg=-flto -Clink-arg=-fuse-ld=lld" cargo +stable build --release

[heftig]

In https://bugzilla.mozilla.org/show_bug.cgi?id=1654465, Mozilla is switching from setting CARGO_PROFILE_RELEASE_LTO=true to -Cembed-bitcode=yes (for Rust 1.45+ only), but this does not seem to affect this issue.

fails   : RUSTFLAGS="-Clinker-plugin-lto=LLVMgold.so" cargo +stable build --release
succeeds: RUSTFLAGS="-Clinker-plugin-lto=LLVMgold.so" cargo +1.44.1 build --release
fails   : RUSTFLAGS="-Clinker-plugin-lto=LLVMgold.so -Cembed-bitcode=yes" cargo +stable build --release

fails   : CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang RUSTFLAGS="-Clinker-plugin-lto -Clink-arg=-flto" cargo +stable build --release
succeeds: CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang RUSTFLAGS="-Clinker-plugin-lto -Clink-arg=-flto" cargo +1.44.1 build --release
fails   : CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang RUSTFLAGS="-Clinker-plugin-lto -Cembed-bitcode=yes -Clink-arg=-flto" cargo +stable build --release

succeeds: RUSTFLAGS="-Clinker-plugin-lto=LLVMgold.so -Clink-arg=-fuse-ld=gold" cargo +stable build --release
succeeds: RUSTFLAGS="-Clinker-plugin-lto=LLVMgold.so -Clink-arg=-fuse-ld=lld" cargo +stable build --release
succeeds: RUSTFLAGS="-Clinker-plugin-lto=LLVMgold.so -Cembed-bitcode=yes -Clink-arg=-fuse-ld=gold" cargo +stable build --release
succeeds: RUSTFLAGS="-Clinker-plugin-lto=LLVMgold.so -Cembed-bitcode=yes -Clink-arg=-fuse-ld=lld" cargo +stable build --release

succeeds: CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang RUSTFLAGS="-Clinker-plugin-lto -Clink-arg=-flto -Clink-arg=-fuse-ld=gold" cargo +stable build --release
succeeds: CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang RUSTFLAGS="-Clinker-plugin-lto -Clink-arg=-flto -Clink-arg=-fuse-ld=lld" cargo +stable build --release
succeeds: CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang RUSTFLAGS="-Clinker-plugin-lto -Cembed-bitcode=yes -Clink-arg=-flto -Clink-arg=-fuse-ld=gold" cargo +stable build --release
succeeds: CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang RUSTFLAGS="-Clinker-plugin-lto -Cembed-bitcode=yes -Clink-arg=-flto -Clink-arg=-fuse-ld=lld" cargo +stable build --release

[foutrelis]

The issue is also reproducible on Ubuntu 20.04 with rust 1.45.0 installed using rustup.rs. Bisecting points to 1357af3 which sounds relevant.

For the bisect, I used cargo-bisect-rustc to test if rusqlite builds with RUSTFLAGS="-Clinker-plugin-lto=LLVMgold.so" cargo build --release.

[spastorino]

@rustbot ping cleanup

To see if we can minimize this issue.

[rustbot]

Hey Cleanup Crew ICE-breakers! This bug has been identified as a good
"Cleanup ICE-breaking candidate". In case it's useful, here are some
instructions for tackling these sorts of bugs. Maybe take a look?
Thanks! <3

cc @AminArria @camelid @chrissimpkins @contrun @DutchGhost @elshize @ethanboxx @h-michael @HallerPatrick @hdhoang @hellow554 @imtsuki @kanru @KarlK90 @LeSeulArtichaut @MAdrianMattocks @matheus-consoli @mental32 @nmccarty @Noah-Kennedy @pard68 @PeytonT @pierreN @Redblueflame @RobbieClarken @RobertoSnap @robjtede @SarthakSingh31 @senden9 @shekohex @sinato @spastorino @turboladen @woshilapin @yerke

[spastorino]

Assigning P-highmeanwhile we figure out more information about this issue, as discussed as part of the Prioritization Working Group procedure and removing I-prioritize.