From b67271507d5a26416f83f1afe0e8f43cc77567ba Mon Sep 17 00:00:00 2001 From: Daniil Belov Date: Mon, 15 Aug 2022 13:15:01 +0300 Subject: change stdlib circular dependencies handling --- compiler/rustc_codegen_ssa/src/back/link.rs | 68 ++++----------------------- compiler/rustc_codegen_ssa/src/back/linker.rs | 42 ----------------- 2 files changed, 8 insertions(+), 102 deletions(-) (limited to 'compiler/rustc_codegen_ssa/src/back') diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs index e9171823c24..d37a2cc8c8e 100644 --- a/compiler/rustc_codegen_ssa/src/back/link.rs +++ b/compiler/rustc_codegen_ssa/src/back/link.rs @@ -1,6 +1,6 @@ use rustc_arena::TypedArena; use rustc_ast::CRATE_NODE_ID; -use rustc_data_structures::fx::{FxHashSet, FxIndexMap}; +use rustc_data_structures::fx::FxIndexMap; use rustc_data_structures::memmap::Mmap; use rustc_data_structures::temp_dir::MaybeTempDir; use rustc_errors::{ErrorGuaranteed, Handler}; @@ -1714,6 +1714,13 @@ fn add_post_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor /// that are necessary for the linking. They are only present in symbol table but not actually /// used in any sections, so the linker will therefore pick relevant rlibs for linking, but /// unused `#[no_mangle]` or `#[used]` can still be discard by GC sections. +/// +/// There's a few internal crates in the standard library (aka libcore and +/// libstd) which actually have a circular dependence upon one another. This +/// currently arises through "weak lang items" where libcore requires things +/// like `rust_begin_unwind` but libstd ends up defining it. To get this +/// circular dependence to work correctly we declare some of these things +/// in this synthetic object. fn add_linked_symbol_object( cmd: &mut dyn Linker, sess: &Session, @@ -2333,65 +2340,10 @@ fn add_upstream_rust_crates<'a>( // crates. let deps = &codegen_results.crate_info.used_crates; - // There's a few internal crates in the standard library (aka libcore and - // libstd) which actually have a circular dependence upon one another. This - // currently arises through "weak lang items" where libcore requires things - // like `rust_begin_unwind` but libstd ends up defining it. To get this - // circular dependence to work correctly in all situations we'll need to be - // sure to correctly apply the `--start-group` and `--end-group` options to - // GNU linkers, otherwise if we don't use any other symbol from the standard - // library it'll get discarded and the whole application won't link. - // - // In this loop we're calculating the `group_end`, after which crate to - // pass `--end-group` and `group_start`, before which crate to pass - // `--start-group`. We currently do this by passing `--end-group` after - // the first crate (when iterating backwards) that requires a lang item - // defined somewhere else. Once that's set then when we've defined all the - // necessary lang items we'll pass `--start-group`. - // - // Note that this isn't amazing logic for now but it should do the trick - // for the current implementation of the standard library. - let mut group_end = None; - let mut group_start = None; - // Crates available for linking thus far. - let mut available = FxHashSet::default(); - // Crates required to satisfy dependencies discovered so far. - let mut required = FxHashSet::default(); - - let info = &codegen_results.crate_info; - for &cnum in deps.iter().rev() { - if let Some(missing) = info.missing_lang_items.get(&cnum) { - let missing_crates = missing.iter().map(|i| info.lang_item_to_crate.get(i).copied()); - required.extend(missing_crates); - } - - required.insert(Some(cnum)); - available.insert(Some(cnum)); - - if required.len() > available.len() && group_end.is_none() { - group_end = Some(cnum); - } - if required.len() == available.len() && group_end.is_some() { - group_start = Some(cnum); - break; - } - } - - // If we didn't end up filling in all lang items from upstream crates then - // we'll be filling it in with our crate. This probably means we're the - // standard library itself, so skip this for now. - if group_end.is_some() && group_start.is_none() { - group_end = None; - } - let mut compiler_builtins = None; let search_path = OnceCell::new(); for &cnum in deps.iter() { - if group_start == Some(cnum) { - cmd.group_start(); - } - // We may not pass all crates through to the linker. Some crates may // appear statically in an existing dylib, meaning we'll pick up all the // symbols from the dylib. @@ -2470,10 +2422,6 @@ fn add_upstream_rust_crates<'a>( } Linkage::Dynamic => add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0), } - - if group_end == Some(cnum) { - cmd.group_end(); - } } // compiler-builtins are always placed last to ensure that they're diff --git a/compiler/rustc_codegen_ssa/src/back/linker.rs b/compiler/rustc_codegen_ssa/src/back/linker.rs index 8c6f526b054..949a356fce1 100644 --- a/compiler/rustc_codegen_ssa/src/back/linker.rs +++ b/compiler/rustc_codegen_ssa/src/back/linker.rs @@ -183,8 +183,6 @@ pub trait Linker { fn no_default_libraries(&mut self); fn export_symbols(&mut self, tmpdir: &Path, crate_type: CrateType, symbols: &[String]); fn subsystem(&mut self, subsystem: &str); - fn group_start(&mut self); - fn group_end(&mut self); fn linker_plugin_lto(&mut self); fn add_eh_frame_header(&mut self) {} fn add_no_exec(&mut self) {} @@ -730,18 +728,6 @@ impl<'a> Linker for GccLinker<'a> { self.hint_dynamic(); // Reset to default before returning the composed command line. } - fn group_start(&mut self) { - if self.takes_hints() { - self.linker_arg("--start-group"); - } - } - - fn group_end(&mut self) { - if self.takes_hints() { - self.linker_arg("--end-group"); - } - } - fn linker_plugin_lto(&mut self) { match self.sess.opts.cg.linker_plugin_lto { LinkerPluginLto::Disabled => { @@ -1019,10 +1005,6 @@ impl<'a> Linker for MsvcLinker<'a> { } } - // MSVC doesn't need group indicators - fn group_start(&mut self) {} - fn group_end(&mut self) {} - fn linker_plugin_lto(&mut self) { // Do nothing } @@ -1165,10 +1147,6 @@ impl<'a> Linker for EmLinker<'a> { // noop } - // Appears not necessary on Emscripten - fn group_start(&mut self) {} - fn group_end(&mut self) {} - fn linker_plugin_lto(&mut self) { // Do nothing } @@ -1344,10 +1322,6 @@ impl<'a> Linker for WasmLd<'a> { fn subsystem(&mut self, _subsystem: &str) {} - // Not needed for now with LLD - fn group_start(&mut self) {} - fn group_end(&mut self) {} - fn linker_plugin_lto(&mut self) { // Do nothing for now } @@ -1476,14 +1450,6 @@ impl<'a> Linker for L4Bender<'a> { self.hint_static(); // Reset to default before returning the composed command line. } - fn group_start(&mut self) { - self.cmd.arg("--start-group"); - } - - fn group_end(&mut self) { - self.cmd.arg("--end-group"); - } - fn linker_plugin_lto(&mut self) {} fn control_flow_guard(&mut self) {} @@ -1664,10 +1630,6 @@ impl<'a> Linker for PtxLinker<'a> { fn subsystem(&mut self, _subsystem: &str) {} - fn group_start(&mut self) {} - - fn group_end(&mut self) {} - fn linker_plugin_lto(&mut self) {} } @@ -1777,9 +1739,5 @@ impl<'a> Linker for BpfLinker<'a> { fn subsystem(&mut self, _subsystem: &str) {} - fn group_start(&mut self) {} - - fn group_end(&mut self) {} - fn linker_plugin_lto(&mut self) {} } -- cgit 1.4.1-3-g733a5