From b67b5a8d0149096712e75336f6aa32daffcaa42d Mon Sep 17 00:00:00 2001 From: Alex Crichton Date: Thu, 10 Dec 2015 12:21:55 -0800 Subject: [PATCH] rustc: Add feature-gated cfg(target_thread_local) Currently the standard library has some pretty complicated logic to detect whether #[thread_local] should be used or whether it's supported. This is also unfortunately not quite true for OSX where not all versions support the #[thread_local] attribute (only 10.7+ does). Compiling code for OSX 10.6 is typically requested via the MACOSX_DEPLOYMENT_TARGET environment variable (e.g. the linker recognizes this), but the standard library unfortunately does not respect this. This commit updates the compiler to add a `target_thread_local` cfg annotation if the platform being targeted supports the `#[thread_local]` attribute. This is feature gated for now, and it is only true on non-aarch64 Linux and 10.7+ OSX (e.g. what the module already does today). Logic has also been added to parse the deployment target environment variable. --- src/librustc/session/config.rs | 3 +++ .../target/aarch64_unknown_linux_gnu.rs | 3 ++- src/librustc_back/target/apple_base.rs | 23 ++++++++++++++++++- src/librustc_back/target/apple_ios_base.rs | 1 + .../target/arm_linux_androideabi.rs | 1 + src/librustc_back/target/linux_base.rs | 1 + src/librustc_back/target/mod.rs | 5 ++++ src/libsyntax/feature_gate.rs | 8 +++++++ 8 files changed, 43 insertions(+), 2 deletions(-) diff --git a/src/librustc/session/config.rs b/src/librustc/session/config.rs index e33fe9570c0..b275480a6fc 100644 --- a/src/librustc/session/config.rs +++ b/src/librustc/session/config.rs @@ -660,6 +660,9 @@ pub fn default_configuration(sess: &Session) -> ast::CrateConfig { "windows" | "unix" => ret.push(attr::mk_word_item(fam)), _ => (), } + if sess.target.target.options.has_elf_tls { + ret.push(attr::mk_word_item(InternedString::new("target_thread_local"))); + } if sess.opts.debug_assertions { ret.push(attr::mk_word_item(InternedString::new("debug_assertions"))); } diff --git a/src/librustc_back/target/aarch64_unknown_linux_gnu.rs b/src/librustc_back/target/aarch64_unknown_linux_gnu.rs index 51abab6609a..21bfd87e412 100644 --- a/src/librustc_back/target/aarch64_unknown_linux_gnu.rs +++ b/src/librustc_back/target/aarch64_unknown_linux_gnu.rs @@ -11,7 +11,8 @@ use target::Target; pub fn target() -> Target { - let base = super::linux_base::opts(); + let mut base = super::linux_base::opts(); + base.has_elf_tls = false; Target { llvm_target: "aarch64-unknown-linux-gnu".to_string(), target_endian: "little".to_string(), diff --git a/src/librustc_back/target/apple_base.rs b/src/librustc_back/target/apple_base.rs index 8b75bb39414..ffcb6f971ae 100644 --- a/src/librustc_back/target/apple_base.rs +++ b/src/librustc_back/target/apple_base.rs @@ -8,10 +8,30 @@ // option. This file may not be copied, modified, or distributed // except according to those terms. +use std::env; + use target::TargetOptions; -use std::default::Default; pub fn opts() -> TargetOptions { + // ELF TLS is only available in OSX 10.7+. If you try to compile for 10.6 + // either the linker will complain if it is used or the binary will end up + // segfaulting at runtime when run on 10.6. Rust by default supports OSX + // 10.7+, but there is a standard environment variable, + // MACOSX_DEPLOYMENT_TARGET, which is used to signal targeting older + // versions of OSX. For example compiling on 10.10 with + // MACOSX_DEPLOYMENT_TARGET set to 10.6 will cause the linker to generate + // warnings about the usage of ELF TLS. + // + // Here we detect what version is being requested, defaulting to 10.7. ELF + // TLS is flagged as enabled if it looks to be supported. + let deployment_target = env::var("MACOSX_DEPLOYMENT_TARGET").ok(); + let version = deployment_target.as_ref().and_then(|s| { + let mut i = s.splitn(2, "."); + i.next().and_then(|a| i.next().map(|b| (a, b))) + }).and_then(|(a, b)| { + a.parse::().and_then(|a| b.parse::().map(|b| (a, b))).ok() + }).unwrap_or((10, 7)); + TargetOptions { // OSX has -dead_strip, which doesn't rely on ffunction_sections function_sections: false, @@ -25,6 +45,7 @@ pub fn opts() -> TargetOptions { archive_format: "bsd".to_string(), pre_link_args: Vec::new(), exe_allocation_crate: super::maybe_jemalloc(), + has_elf_tls: version >= (10, 7), .. Default::default() } } diff --git a/src/librustc_back/target/apple_ios_base.rs b/src/librustc_back/target/apple_ios_base.rs index 77030f5d768..d182fd96056 100644 --- a/src/librustc_back/target/apple_ios_base.rs +++ b/src/librustc_back/target/apple_ios_base.rs @@ -88,6 +88,7 @@ pub fn opts(arch: Arch) -> TargetOptions { dynamic_linking: false, executables: true, pre_link_args: pre_link_args(arch), + has_elf_tls: false, .. super::apple_base::opts() } } diff --git a/src/librustc_back/target/arm_linux_androideabi.rs b/src/librustc_back/target/arm_linux_androideabi.rs index 732f1a353a8..7776aaacd00 100644 --- a/src/librustc_back/target/arm_linux_androideabi.rs +++ b/src/librustc_back/target/arm_linux_androideabi.rs @@ -13,6 +13,7 @@ use target::Target; pub fn target() -> Target { let mut base = super::android_base::opts(); base.features = "+v7".to_string(); + base.has_elf_tls = false; Target { llvm_target: "arm-linux-androideabi".to_string(), diff --git a/src/librustc_back/target/linux_base.rs b/src/librustc_back/target/linux_base.rs index 6492fa50159..0efcf73ee86 100644 --- a/src/librustc_back/target/linux_base.rs +++ b/src/librustc_back/target/linux_base.rs @@ -30,6 +30,7 @@ pub fn opts() -> TargetOptions { position_independent_executables: true, archive_format: "gnu".to_string(), exe_allocation_crate: super::maybe_jemalloc(), + has_elf_tls: true, .. Default::default() } } diff --git a/src/librustc_back/target/mod.rs b/src/librustc_back/target/mod.rs index f259698a220..666903b4eed 100644 --- a/src/librustc_back/target/mod.rs +++ b/src/librustc_back/target/mod.rs @@ -195,6 +195,10 @@ pub struct TargetOptions { /// Default crate for allocation symbols to link against pub lib_allocation_crate: String, pub exe_allocation_crate: String, + + /// Flag indicating whether ELF TLS (e.g. #[thread_local]) is available for + /// this target. + pub has_elf_tls: bool, } impl Default for TargetOptions { @@ -240,6 +244,7 @@ impl Default for TargetOptions { lib_allocation_crate: "alloc_system".to_string(), exe_allocation_crate: "alloc_system".to_string(), allow_asm: true, + has_elf_tls: false, } } } diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs index b2989c42a9e..390e8253dcf 100644 --- a/src/libsyntax/feature_gate.rs +++ b/src/libsyntax/feature_gate.rs @@ -236,6 +236,9 @@ const KNOWN_FEATURES: &'static [(&'static str, &'static str, Option, Status // allow using type ascription in expressions ("type_ascription", "1.6.0", Some(23416), Active), + + // Allows cfg(target_thread_local) + ("cfg_target_thread_local", "1.7.0", Some(26581), Active), ]; // (changing above list without updating src/doc/reference.md makes @cmr sad) @@ -414,6 +417,8 @@ const GATED_CFGS: &'static [(&'static str, &'static str, fn(&Features) -> bool)] // (name in cfg, feature, function to check if the feature is enabled) ("target_feature", "cfg_target_feature", cfg_fn!(|x| x.cfg_target_feature)), ("target_vendor", "cfg_target_vendor", cfg_fn!(|x| x.cfg_target_vendor)), + ("target_thread_local", "cfg_target_thread_local", + cfg_fn!(|x| x.cfg_target_thread_local)), ]; #[derive(Debug, Eq, PartialEq)] @@ -541,6 +546,7 @@ pub struct Features { pub type_macros: bool, pub cfg_target_feature: bool, pub cfg_target_vendor: bool, + pub cfg_target_thread_local: bool, pub augmented_assignments: bool, pub braced_empty_structs: bool, pub staged_api: bool, @@ -575,6 +581,7 @@ impl Features { type_macros: false, cfg_target_feature: false, cfg_target_vendor: false, + cfg_target_thread_local: false, augmented_assignments: false, braced_empty_structs: false, staged_api: false, @@ -1157,6 +1164,7 @@ fn check_crate_inner(cm: &CodeMap, span_handler: &Handler, type_macros: cx.has_feature("type_macros"), cfg_target_feature: cx.has_feature("cfg_target_feature"), cfg_target_vendor: cx.has_feature("cfg_target_vendor"), + cfg_target_thread_local: cx.has_feature("cfg_target_thread_local"), augmented_assignments: cx.has_feature("augmented_assignments"), braced_empty_structs: cx.has_feature("braced_empty_structs"), staged_api: cx.has_feature("staged_api"),