From c721fa243825255c0f195d4282021e7c263c3e7f Mon Sep 17 00:00:00 2001 From: iximeow Date: Sun, 28 Sep 2025 03:21:45 +0000 Subject: interpret #[used] as #[used(compiler)] on illumos illumos' `ld` does not support a flag like either SHF_GNU_RETAIN or SHF_SUNW_NODISCARD, so there is no way to communicate `#[used(linker)]` for that target. Setting `USED_LINKER` to try results in LLVM setting SHF_SUNW_NODISCARD for Solaris-like targets, which is an unknown section header flag for illumos `ld` and prevents sections from being merged that otherwise would. As a motivating example, the `inventory` crate produces `#[used]` items to merge into `.init_array`. Because those items have an unknown section header flag they are not merged with the default `.init_array` with `frame_dummy`, and end up never executed. Downgrading `#[used]` to `#[used(compiler)]` on illumos keeps so-attributed items as preserved as they had been before https://github.com/rust-lang/rust/pull/140872. As was the case before that change, because rustc passes `-z ignore` to illumos `ld`, it's possible that `used` sections are GC'd at link time. https://github.com/rust-lang/rust/issues/146169 describes this unfortunate circumstance. --- compiler/rustc_codegen_ssa/src/codegen_attrs.rs | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'compiler/rustc_codegen_ssa/src') diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs index 32ae810ecc8..2c7643e46ce 100644 --- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs +++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs @@ -263,6 +263,19 @@ fn process_builtin_attrs( AttributeKind::Used { used_by, .. } => match used_by { UsedBy::Compiler => codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_COMPILER, UsedBy::Linker => codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_LINKER, + UsedBy::Default => { + let used_form = if tcx.sess.target.os == "illumos" { + // illumos' `ld` doesn't support a section header that would represent + // `#[used(linker)]`, see + // https://github.com/rust-lang/rust/issues/146169. For that target, + // downgrade as if `#[used(compiler)]` was requested and hope for the + // best. + CodegenFnAttrFlags::USED_COMPILER + } else { + CodegenFnAttrFlags::USED_LINKER + }; + codegen_fn_attrs.flags |= used_form; + } }, AttributeKind::FfiConst(_) => { codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST -- cgit 1.4.1-3-g733a5