From 31c2ad0d4cdd06622353a57b3a678586077b84fe Mon Sep 17 00:00:00 2001 From: "Joshua M. Clulow" Date: Thu, 6 May 2021 17:01:50 -0700 Subject: [PATCH] illumos should put libc last in library search order Under some conditions, the toolchain will produce a sequence of linker arguments that result in a NEEDED list that puts libc before libgcc_s; e.g., [0] NEEDED 0x2046ba libc.so.1 [1] NEEDED 0x204723 libm.so.2 [2] NEEDED 0x204736 libsocket.so.1 [3] NEEDED 0x20478b libumem.so.1 [4] NEEDED 0x204763 libgcc_s.so.1 Both libc and libgcc_s provide an unwinder implementation, but libgcc_s provides some extra symbols upon which Rust directly depends. If libc is first in the NEEDED list we will find some of those symbols in libc but others in libgcc_s, resulting in undefined behaviour as the two implementations do not use compatible interior data structures. This solution is not perfect, but is the simplest way to produce correct binaries on illumos for now. --- compiler/rustc_codegen_ssa/src/back/linker.rs | 8 ++++++++ compiler/rustc_target/src/spec/illumos_base.rs | 11 +++++++++++ 2 files changed, 19 insertions(+) diff --git a/compiler/rustc_codegen_ssa/src/back/linker.rs b/compiler/rustc_codegen_ssa/src/back/linker.rs index 401d379b0d161..a66de89f68179 100644 --- a/compiler/rustc_codegen_ssa/src/back/linker.rs +++ b/compiler/rustc_codegen_ssa/src/back/linker.rs @@ -340,6 +340,14 @@ impl<'a> Linker for GccLinker<'a> { } fn link_dylib(&mut self, lib: Symbol, verbatim: bool, as_needed: bool) { + if self.sess.target.os == "illumos" && lib.as_str() == "c" { + // libc will be added via late_link_args on illumos so that it will + // appear last in the library search order. + // FIXME: This should be replaced by a more complete and generic + // mechanism for controlling the order of library arguments passed + // to the linker. + return; + } if !as_needed { if self.sess.target.is_like_osx { // FIXME(81490): ld64 doesn't support these flags but macOS 11 diff --git a/compiler/rustc_target/src/spec/illumos_base.rs b/compiler/rustc_target/src/spec/illumos_base.rs index 2e365d210f3f6..2b8e046c46b0e 100644 --- a/compiler/rustc_target/src/spec/illumos_base.rs +++ b/compiler/rustc_target/src/spec/illumos_base.rs @@ -6,6 +6,17 @@ pub fn opts() -> TargetOptions { late_link_args.insert( LinkerFlavor::Gcc, vec![ + // The illumos libc contains a stack unwinding implementation, as + // does libgcc_s. The latter implementation includes several + // additional symbols that are not always in base libc. To force + // the consistent use of just one unwinder, we ensure libc appears + // after libgcc_s in the NEEDED list for the resultant binary by + // ignoring any attempts to add it as a dynamic dependency until the + // very end. + // FIXME: This should be replaced by a more complete and generic + // mechanism for controlling the order of library arguments passed + // to the linker. + "-lc".to_string(), // LLVM will insert calls to the stack protector functions // "__stack_chk_fail" and "__stack_chk_guard" into code in native // object files. Some platforms include these symbols directly in