extern_weak linkage on definition not rejected

[matthiaskrgr]

I tried this code:

#![feature(linkage)]
#![crate_type = "rlib"]

#[linkage = "extern_weak"]
pub static EXTERN: u32 = 42;

Meta

rustc --version --verbose:

rustc 1.87.0-nightly (617aad8c2 2025-02-24)
binary: rustc
commit-hash: 617aad8c2e8783f6df8e5d1f8bb1e4bcdc70aa7b
commit-date: 2025-02-24
host: x86_64-unknown-linux-gnu
release: 1.87.0-nightly
LLVM version: 20.1.0

Backtrace

error: rustc interrupted by SIGILL, printing backtrace

/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-19054624313a00ee.so(+0x37010df) [0x7cb3fc7010df]
/usr/lib/libc.so.6(+0x3dcd0) [0x7cb3f8e4bcd0]
/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/libLLVM.so.20.1-rust-1.87.0-nightly(+0x8bd2096) [0x7cb3f7dd2096]
/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/libLLVM.so.20.1-rust-1.87.0-nightly(_ZN4llvm10AsmPrinter18emitGlobalVariableEPKNS_14GlobalVariableE+0x35a) [0x7cb3f70e40da]
/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/libLLVM.so.20.1-rust-1.87.0-nightly(_ZN4llvm10AsmPrinter14doFinalizationERNS_6ModuleE+0x219) [0x7cb3f70e546d]
/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/libLLVM.so.20.1-rust-1.87.0-nightly(_ZN4llvm13FPPassManager14doFinalizationERNS_6ModuleE+0x2a) [0x7cb3f702a2ea]
/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/libLLVM.so.20.1-rust-1.87.0-nightly(_ZN4llvm6legacy15PassManagerImpl3runERNS_6ModuleE+0x3ff) [0x7cb3f7634493]
/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-19054624313a00ee.so(+0x5bb8b82) [0x7cb3febb8b82]
/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-19054624313a00ee.so(+0x5bb86e1) [0x7cb3febb86e1]
/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-19054624313a00ee.so(+0x5bb5e33) [0x7cb3febb5e33]
/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-19054624313a00ee.so(+0x5bb5ae8) [0x7cb3febb5ae8]
/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-19054624313a00ee.so(_RINvNtNtCs5JDsLVAy2fO_3std3sys9backtrace28___rust_begin_short_backtraceNCINvXs0_Cs2p9PGD2gg2l_18rustc_codegen_llvmNtB1g_18LlvmCodegenBackendNtNtNtCsjc85tVovh2m_17rustc_codegen_ssa6traits7backend19ExtraBackendMethods18spawn_named_threadNCINvNtNtB2k_4back5write10spawn_workB1O_E0uE0uEB1g_+0x2eb) [0x7cb3febb452b]
/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-19054624313a00ee.so(+0x5bad822) [0x7cb3febad822]
/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-19054624313a00ee.so(+0x5bad2ab) [0x7cb3febad2ab]
/usr/lib/libc.so.6(+0x9570a) [0x7cb3f8ea370a]
/usr/lib/libc.so.6(+0x119aac) [0x7cb3f8f27aac]

note: we would appreciate a report at https://github.com/rust-lang/rust
[1]    4158672 illegal hardware instruction  RUST_BACKTRACE=full rustc a.rs

[matthiaskrgr]

llvm bitcode

; ModuleID = 'a.c51f459b1bd73179-cgu.0'
source_filename = "a.c51f459b1bd73179-cgu.0"
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

@_ZN1a6EXTERN17h4f3857837f588658E = extern_weak constant <{ [4 x i8] }> <{ [4 x i8] c"*\00\00\00" }>, align 4

!llvm.module.flags = !{!0, !1}
!llvm.ident = !{!2}

!0 = !{i32 8, !"PIC Level", i32 2}
!1 = !{i32 2, !"RtLibUseGOT", i32 1}
!2 = !{!"rustc version 1.87.0-nightly (617aad8c2 2025-02-24)"}

[nikic]

extern_weak linkage is only legal on extern declarations (duh). The global cannot have an initializer.

This is very similar to #109681, in that Rust currently does not verify #[linkage] validity.