x86_64-pc-windows-gnu can't link libtest with LTO=thin

[ehuss]

x86_64-pc-windows-gnu is unable to build a test binary with LTO=thin.

Reproduction:

1. touch foo.rs
2. rustc +nightly-x86_64-pc-windows-gnu -Clto=thin --test foo.rs

Error:

error: linking with `x86_64-w64-mingw32-gcc` failed: exit code: 1
  |
  = note: "x86_64-w64-mingw32-gcc" "-fno-use-linker-plugin" "-Wl,--dynamicbase" "-Wl,--disable-auto-image-base" "-m64" "-Wl,--high-entropy-va" "C:\\Users\\User\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\self-contained\\crt2.o" "C:\\Users\\User\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\rsbegin.o" "C:\\Users\\User\\AppData\\Local\\Temp\\rustcSapTY6\\symbols.o" "foo.58ka7t7dknl8118b.rcgu.o" "foo.addr2line-14c0744e763fbcc5.addr2line.a755ea22-cgu.0.rcgu.o.rcgu.o" "foo.adler-67dc86611d2bf020.adler.5bb2de54-cgu.0.rcgu.o.rcgu.o" "foo.alloc-366e8128b0a2151f.alloc.0e2959ea-cgu.0.rcgu.o.rcgu.o" "foo.cfg_if-22b8dcc08139ebd4.cfg_if.4a5ba149-cgu.0.rcgu.o.rcgu.o" "foo.core-0e5c5feeef4bd6da.core.35109205-cgu.0.rcgu.o.rcgu.o" "foo.foo.f94f5f32-cgu.0.rcgu.o" "foo.foo.f94f5f32-cgu.1.rcgu.o" "foo.foo.f94f5f32-cgu.2.rcgu.o" "foo.foo.f94f5f32-cgu.3.rcgu.o" "foo.foo.f94f5f32-cgu.4.rcgu.o" "foo.getopts-7a2ff2879c4becfe.getopts.27ae8826-cgu.0.rcgu.o.rcgu.o" "foo.gimli-281c67c7290209a3.gimli.b3006d85-cgu.0.rcgu.o.rcgu.o" "foo.hashbrown-73dc3622ac20c1ad.hashbrown.4fd96bfe-cgu.0.rcgu.o.rcgu.o" "foo.libc-8e4d63370c2f2f4b.libc.43b5f33f-cgu.0.rcgu.o.rcgu.o" "foo.memchr-4164db77eca254c1.memchr.bf2fc5a0-cgu.0.rcgu.o.rcgu.o" "foo.miniz_oxide-753b0ac42b327310.miniz_oxide.f6d02d85-cgu.0.rcgu.o.rcgu.o" "foo.object-fd18c1e2427b7d66.object.c948ec4e-cgu.0.rcgu.o.rcgu.o" "foo.panic_unwind-cd212035a0d658c8.panic_unwind.b47531a0-cgu.0.rcgu.o.rcgu.o" "foo.rustc_demangle-378d74d608afb5ce.rustc_demangle.15cbba0f-cgu.0.rcgu.o.rcgu.o" "foo.rustc_std_workspace_alloc-0279e801977a0519.rustc_std_workspace_alloc.3d4a570e-cgu.0.rcgu.o.rcgu.o" "foo.rustc_std_workspace_core-043dcb5cef4e65e2.rustc_std_workspace_core.7d396b72-cgu.0.rcgu.o.rcgu.o" "foo.rustc_std_workspace_std-924aa08e8fb30081.rustc_std_workspace_std.cfad5f07-cgu.0.rcgu.o.rcgu.o" "foo.std-67692f6c6473d324.std.14d27bce-cgu.0.rcgu.o.rcgu.o" "foo.std_detect-ac29a076266feb38.std_detect.3a222bf1-cgu.0.rcgu.o.rcgu.o" "foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o" "foo.unicode_width-4cda36558020d9a8.unicode_width.7d30b2de-cgu.0.rcgu.o.rcgu.o" "foo.unwind-d6953a7e39d3701d.unwind.aac5024c-cgu.0.rcgu.o.rcgu.o" "-L" "C:\\Users\\User\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib" "-Wl,-Bstatic" "C:\\Users\\User\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\libcompiler_builtins-1e8650baf8073116.rlib" "-Wl,-Bdynamic" "-lkernel32" "-lkernel32" "-ladvapi32" "-luserenv" "-lkernel32" "-lws2_32" "-lbcrypt" "-lgcc_eh" "-l:libpthread.a" "-lmsvcrt" "-lmingwex" "-lmingw32" "-lgcc" "-lmsvcrt" "-luser32" "-lkernel32" "-Wl,--nxcompat" "-nostartfiles" "-L" "C:\\Users\\User\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib" "-L" "C:\\Users\\User\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\self-contained" "-o" "foo.exe" "-Wl,--gc-sections" "-no-pie" "-nodefaultlibs" "C:\\Users\\User\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\rsend.o"
  = note: foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o: In function `core::sync::atomic::atomic_load::h1ce09cb4e3d2295f':
          /rustc/70f8737b2f5d3bf7d6b784fad00b663b7ff9feda/library\core\src\sync/atomic.rs:2988: undefined reference to `__imp__ZN3std11collections4hash3map11RandomState3new4KEYS7__getit5__KEY17h4d133909dffb598dE'
          foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o: In function `std::sys::windows::thread_local_key::StaticKey::key::h5a360baef9e4385d':
          /rustc/70f8737b2f5d3bf7d6b784fad00b663b7ff9feda/library\std\src\sys\windows/thread_local_key.rs:79: undefined reference to `__imp__ZN3std11collections4hash3map11RandomState3new4KEYS7__getit5__KEY17h4d133909dffb598dE'
          foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o: In function `core::sync::atomic::atomic_load::h1ce09cb4e3d2295f':
          /rustc/70f8737b2f5d3bf7d6b784fad00b663b7ff9feda/library\core\src\sync/atomic.rs:2988: undefined reference to `__imp__ZN3std11collections4hash3map11RandomState3new4KEYS7__getit5__KEY17h4d133909dffb598dE'
          foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o: In function `std::sys::windows::thread_local_key::StaticKey::key::h5a360baef9e4385d':
          /rustc/70f8737b2f5d3bf7d6b784fad00b663b7ff9feda/library\std\src\sys\windows/thread_local_key.rs:79: undefined reference to `__imp__ZN3std11collections4hash3map11RandomState3new4KEYS7__getit5__KEY17h4d133909dffb598dE'
          foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o: In function `std::thread::local::os::Key$LT$T$GT$::try_initialize::ha296643cb4ec4997':
          /rustc/70f8737b2f5d3bf7d6b784fad00b663b7ff9feda/library\std\src\thread/local.rs:1118: undefined reference to `__imp__ZN3std11collections4hash3map11RandomState3new4KEYS7__getit5__KEY17h4d133909dffb598dE'
          foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o:/rustc/70f8737b2f5d3bf7d6b784fad00b663b7ff9feda/library\std\src\sys\windows/thread_local_key.rs:79: more undefined references to `__imp__ZN3std11collections4hash3map11RandomState3new4KEYS7__getit5__KEY17h4d133909dffb598dE' follow
          foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o: In function `core::sync::atomic::atomic_load::h1ce09cb4e3d2295f':
          /rustc/70f8737b2f5d3bf7d6b784fad00b663b7ff9feda/library\core\src\sync/atomic.rs:2988: undefined reference to `__imp__ZN3std4sync4mpmc5waker17current_thread_id5DUMMY7__getit5__KEY17h1ce21b2969d5bc2bE'
          foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o: In function `std::sys::windows::thread_local_key::StaticKey::key::h5a360baef9e4385d':
          /rustc/70f8737b2f5d3bf7d6b784fad00b663b7ff9feda/library\std\src\sys\windows/thread_local_key.rs:79: undefined reference to `__imp__ZN3std4sync4mpmc5waker17current_thread_id5DUMMY7__getit5__KEY17h1ce21b2969d5bc2bE'
          foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o: In function `core::sync::atomic::atomic_load::h1ce09cb4e3d2295f':
          /rustc/70f8737b2f5d3bf7d6b784fad00b663b7ff9feda/library\core\src\sync/atomic.rs:2988: undefined reference to `__imp__ZN3std4sync4mpmc5waker17current_thread_id5DUMMY7__getit5__KEY17h1ce21b2969d5bc2bE'
          foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o: In function `std::sys::windows::thread_local_key::StaticKey::key::h5a360baef9e4385d':
          /rustc/70f8737b2f5d3bf7d6b784fad00b663b7ff9feda/library\std\src\sys\windows/thread_local_key.rs:79: undefined reference to `__imp__ZN3std4sync4mpmc5waker17current_thread_id5DUMMY7__getit5__KEY17h1ce21b2969d5bc2bE'
          foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o: In function `std::thread::local::os::Key$LT$T$GT$::try_initialize::h2eff52084c9a2c81':
          /rustc/70f8737b2f5d3bf7d6b784fad00b663b7ff9feda/library\std\src\thread/local.rs:1118: undefined reference to `__imp__ZN3std4sync4mpmc5waker17current_thread_id5DUMMY7__getit5__KEY17h1ce21b2969d5bc2bE'
          foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o:/rustc/70f8737b2f5d3bf7d6b784fad00b663b7ff9feda/library\std\src\sys\windows/thread_local_key.rs:79: more undefined references to `__imp__ZN3std4sync4mpmc5waker17current_thread_id5DUMMY7__getit5__KEY17h1ce21b2969d5bc2bE' follow
          foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o: In function `core::sync::atomic::atomic_load::h1ce09cb4e3d2295f':
          /rustc/70f8737b2f5d3bf7d6b784fad00b663b7ff9feda/library\core\src\sync/atomic.rs:2988: undefined reference to `__imp__ZN3std4sync4mpmc7context7Context4with7CONTEXT7__getit5__KEY17h8bce9e2e01c30f57E'
          foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o: In function `std::sys::windows::thread_local_key::StaticKey::key::h5a360baef9e4385d':
          /rustc/70f8737b2f5d3bf7d6b784fad00b663b7ff9feda/library\std\src\sys\windows/thread_local_key.rs:79: undefined reference to `__imp__ZN3std4sync4mpmc7context7Context4with7CONTEXT7__getit5__KEY17h8bce9e2e01c30f57E'
          foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o: In function `core::sync::atomic::atomic_load::h1ce09cb4e3d2295f':
          /rustc/70f8737b2f5d3bf7d6b784fad00b663b7ff9feda/library\core\src\sync/atomic.rs:2988: undefined reference to `__imp__ZN3std4sync4mpmc7context7Context4with7CONTEXT7__getit5__KEY17h8bce9e2e01c30f57E'
          foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o: In function `std::sys::windows::thread_local_key::StaticKey::key::h5a360baef9e4385d':
          /rustc/70f8737b2f5d3bf7d6b784fad00b663b7ff9feda/library\std\src\sys\windows/thread_local_key.rs:79: undefined reference to `__imp__ZN3std4sync4mpmc7context7Context4with7CONTEXT7__getit5__KEY17h8bce9e2e01c30f57E'
          foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o: In function `std::thread::local::os::Key$LT$T$GT$::try_initialize::hc190752f4af349b0':
          /rustc/70f8737b2f5d3bf7d6b784fad00b663b7ff9feda/library\std\src\thread/local.rs:1118: undefined reference to `__imp__ZN3std4sync4mpmc7context7Context4with7CONTEXT7__getit5__KEY17h8bce9e2e01c30f57E'
          foo.test-05c5485ddbae42f3.test.776f7fa2-cgu.0.rcgu.o.rcgu.o:/rustc/70f8737b2f5d3bf7d6b784fad00b663b7ff9feda/library\std\src\sys\windows/thread_local_key.rs:79: more undefined references to `__imp__ZN3std4sync4mpmc7context7Context4with7CONTEXT7__getit5__KEY17h8bce9e2e01c30f57E' follow

  = note: some `extern` functions couldn't be found; some native libraries may need to be installed or have their path specified
  = note: use the `-l` flag to specify native libraries to link
  = note: use the `cargo:rustc-link-lib` directive to specify the native libraries to link with Cargo (see https://doc.rust-lang.org/cargo/reference/build-scripts.html#cargorustc-link-libkindname)

Regression started with #101368.

Meta

rustc --version --verbose:

rustc 1.67.0-nightly (70f8737b2 2022-11-23)
binary: rustc
commit-hash: 70f8737b2f5d3bf7d6b784fad00b663b7ff9feda
commit-date: 2022-11-23
host: x86_64-pc-windows-gnu
release: 1.67.0-nightly
LLVM version: 15.0.4

[thomcc]

This pretty much sucks since it seems like a rustc bug preventing a (admittedly imperfect) soundness fix, but @nikic (#101368 (comment)) and @eddyb (#101368 (comment)) seemed to have a other ideas for how to prevent that issue from happening, so maybe we take the revert here and wait til something can try one of those.

CC @ChrisDenton

[ChrisDenton]

As I said on the revert, I think we do need a proper fix to the underlying issue rather than attempting libs workarounds.

[thomcc]

Hmm, I wonder if we could just do it for target_env = "msvc", since that would at least fix the user's problem in #101368 (comment).

[ChrisDenton]

Maybe. My concern now is that we maybe end up essentially pushing the miscompilation around. So we workaround one problem but maybe we cause another, harder to diagnose, problem somewhere else.

That said, I'm not totally against the idea. Perhaps its a trade off we should make. It doesn't sit particularly well with me though I guess there aren't a lot of good options here.

[ChrisDenton]

Hm, well, thinking about it after a cup of coffee... maybe it's the best trade off. But rather than target_env just don't set it for any windows target that's not also target_thread_local. Something like:

#[cfg_attr(not(windows), inline)]
#[cfg_attr(all(windows, target_thread_local), inline(never))]

Though I'm still not entirely comfortable with all this.

[thomcc]

Yeah, good idea.

[thomcc]

I'll wait on PRing that until I can test the patch in a few different build configurations (to avoid a repeat). That will probably be later this weekend.

[mati865]

Why would it be compiler bug?
If we look at expanded code, the mentioned PR has changed it on *-windows-gnu from:

            unsafe fn __getit(
                init: $crate::option::Option<&mut $crate::option::Option<$t>>,
            ) -> $crate::option::Option<&'static $t> {

to:

            #[inline]
            unsafe fn __getit(
                init: $crate::option::Option<&mut $crate::option::Option<$t>>,
            ) -> $crate::option::Option<&'static $t> {

By the way looks like this could use some unit test to avoid regressions in the future.

[ChrisDenton]

Why would it be compiler bug?

Using the inline attribute on __getit should not be causing linker errors. That is not desirable and so I would personally consider it a bug.

[mati865]

Without target_thread_local this is has a static symbol (so it has to use dllimport/dllexport) and when you are telling compiler to inline it it can easily confuse the linker like we do see with ld.bfd.
Note the same error doesn't appear when linking with LLD.

[ChrisDenton]

But that's a compiler issue. If the gnu linker cannot handle the inlining, then surely gnu toolchains should not be inlining it? The inline attribute does not mean "you must inline this, no matter if it's nonsensical", no?

#[inline] is an optimization hint; from a libs perspective I wouldn't expect it to have any effect on whether or not a program compiles.