// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 or the MIT license // , at your // option. This file may not be copied, modified, or distributed // except according to those terms. use super::archive::{Archive, ArchiveBuilder, ArchiveConfig, METADATA_FILENAME}; use super::archive; use super::rpath; use super::rpath::RPathConfig; use super::svh::Svh; use session::config; use session::config::NoDebugInfo; use session::config::{OutputFilenames, Input, OutputTypeBitcode, OutputTypeExe, OutputTypeObject}; use session::search_paths::PathKind; use session::Session; use metadata::common::LinkMeta; use metadata::{encoder, cstore, filesearch, csearch, creader}; use metadata::filesearch::FileDoesntMatch; use trans::{CrateContext, CrateTranslation, gensym_name}; use middle::ty::{self, Ty}; use util::common::time; use util::ppaux; use util::sha2::{Digest, Sha256}; use std::old_io::fs::PathExtensions; use std::old_io::{fs, TempDir, Command}; use std::old_io; use std::mem; use std::str; use std::string::String; use flate; use serialize::hex::ToHex; use syntax::ast; use syntax::ast_map::{PathElem, PathElems, PathName}; use syntax::attr::AttrMetaMethods; use syntax::codemap::Span; use syntax::parse::token; // RLIB LLVM-BYTECODE OBJECT LAYOUT // Version 1 // Bytes Data // 0..10 "RUST_OBJECT" encoded in ASCII // 11..14 format version as little-endian u32 // 15..22 size in bytes of deflate compressed LLVM bitcode as // little-endian u64 // 23.. compressed LLVM bitcode // This is the "magic number" expected at the beginning of a LLVM bytecode // object in an rlib. pub const RLIB_BYTECODE_OBJECT_MAGIC: &'static [u8] = b"RUST_OBJECT"; // The version number this compiler will write to bytecode objects in rlibs pub const RLIB_BYTECODE_OBJECT_VERSION: u32 = 1; // The offset in bytes the bytecode object format version number can be found at pub const RLIB_BYTECODE_OBJECT_VERSION_OFFSET: uint = 11; // The offset in bytes the size of the compressed bytecode can be found at in // format version 1 pub const RLIB_BYTECODE_OBJECT_V1_DATASIZE_OFFSET: uint = RLIB_BYTECODE_OBJECT_VERSION_OFFSET + 4; // The offset in bytes the compressed LLVM bytecode can be found at in format // version 1 pub const RLIB_BYTECODE_OBJECT_V1_DATA_OFFSET: uint = RLIB_BYTECODE_OBJECT_V1_DATASIZE_OFFSET + 8; /* * Name mangling and its relationship to metadata. This is complex. Read * carefully. * * The semantic model of Rust linkage is, broadly, that "there's no global * namespace" between crates. Our aim is to preserve the illusion of this * model despite the fact that it's not *quite* possible to implement on * modern linkers. We initially didn't use system linkers at all, but have * been convinced of their utility. * * There are a few issues to handle: * * - Linkers operate on a flat namespace, so we have to flatten names. * We do this using the C++ namespace-mangling technique. Foo::bar * symbols and such. * * - Symbols with the same name but different types need to get different * linkage-names. We do this by hashing a string-encoding of the type into * a fixed-size (currently 16-byte hex) cryptographic hash function (CHF: * we use SHA256) to "prevent collisions". This is not airtight but 16 hex * digits on uniform probability means you're going to need 2**32 same-name * symbols in the same process before you're even hitting birthday-paradox * collision probability. * * - Symbols in different crates but with same names "within" the crate need * to get different linkage-names. * * - The hash shown in the filename needs to be predictable and stable for * build tooling integration. It also needs to be using a hash function * which is easy to use from Python, make, etc. * * So here is what we do: * * - Consider the package id; every crate has one (specified with crate_id * attribute). If a package id isn't provided explicitly, we infer a * versionless one from the output name. The version will end up being 0.0 * in this case. CNAME and CVERS are taken from this package id. For * example, github.com/mozilla/CNAME#CVERS. * * - Define CMH as SHA256(crateid). * * - Define CMH8 as the first 8 characters of CMH. * * - Compile our crate to lib CNAME-CMH8-CVERS.so * * - Define STH(sym) as SHA256(CMH, type_str(sym)) * * - Suffix a mangled sym with ::STH@CVERS, so that it is unique in the * name, non-name metadata, and type sense, and versioned in the way * system linkers understand. */ pub fn find_crate_name(sess: Option<&Session>, attrs: &[ast::Attribute], input: &Input) -> String { let validate = |s: String, span: Option| { creader::validate_crate_name(sess, &s[], span); s }; // Look in attributes 100% of the time to make sure the attribute is marked // as used. After doing this, however, we still prioritize a crate name from // the command line over one found in the #[crate_name] attribute. If we // find both we ensure that they're the same later on as well. let attr_crate_name = attrs.iter().find(|at| at.check_name("crate_name")) .and_then(|at| at.value_str().map(|s| (at, s))); if let Some(sess) = sess { if let Some(ref s) = sess.opts.crate_name { if let Some((attr, ref name)) = attr_crate_name { if *s != &name[] { let msg = format!("--crate-name and #[crate_name] are \ required to match, but `{}` != `{}`", s, name); sess.span_err(attr.span, &msg[]); } } return validate(s.clone(), None); } } if let Some((attr, s)) = attr_crate_name { return validate(s.to_string(), Some(attr.span)); } if let Input::File(ref path) = *input { if let Some(s) = path.filestem_str() { return validate(s.to_string(), None); } } "rust-out".to_string() } pub fn build_link_meta(sess: &Session, krate: &ast::Crate, name: String) -> LinkMeta { let r = LinkMeta { crate_name: name, crate_hash: Svh::calculate(&sess.opts.cg.metadata, krate), }; info!("{:?}", r); return r; } fn truncated_hash_result(symbol_hasher: &mut Sha256) -> String { let output = symbol_hasher.result_bytes(); // 64 bits should be enough to avoid collisions. output[.. 8].to_hex().to_string() } // This calculates STH for a symbol, as defined above fn symbol_hash<'tcx>(tcx: &ty::ctxt<'tcx>, symbol_hasher: &mut Sha256, t: Ty<'tcx>, link_meta: &LinkMeta) -> String { // NB: do *not* use abbrevs here as we want the symbol names // to be independent of one another in the crate. symbol_hasher.reset(); symbol_hasher.input_str(&link_meta.crate_name[]); symbol_hasher.input_str("-"); symbol_hasher.input_str(link_meta.crate_hash.as_str()); for meta in &*tcx.sess.crate_metadata.borrow() { symbol_hasher.input_str(&meta[]); } symbol_hasher.input_str("-"); symbol_hasher.input_str(&encoder::encoded_ty(tcx, t)[]); // Prefix with 'h' so that it never blends into adjacent digits let mut hash = String::from_str("h"); hash.push_str(&truncated_hash_result(symbol_hasher)[]); hash } fn get_symbol_hash<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, t: Ty<'tcx>) -> String { match ccx.type_hashcodes().borrow().get(&t) { Some(h) => return h.to_string(), None => {} } let mut symbol_hasher = ccx.symbol_hasher().borrow_mut(); let hash = symbol_hash(ccx.tcx(), &mut *symbol_hasher, t, ccx.link_meta()); ccx.type_hashcodes().borrow_mut().insert(t, hash.clone()); hash } // Name sanitation. LLVM will happily accept identifiers with weird names, but // gas doesn't! // gas accepts the following characters in symbols: a-z, A-Z, 0-9, ., _, $ pub fn sanitize(s: &str) -> String { let mut result = String::new(); for c in s.chars() { match c { // Escape these with $ sequences '@' => result.push_str("$SP$"), '*' => result.push_str("$BP$"), '&' => result.push_str("$RF$"), '<' => result.push_str("$LT$"), '>' => result.push_str("$GT$"), '(' => result.push_str("$LP$"), ')' => result.push_str("$RP$"), ',' => result.push_str("$C$"), // '.' doesn't occur in types and functions, so reuse it // for ':' and '-' '-' | ':' => result.push('.'), // These are legal symbols 'a' ... 'z' | 'A' ... 'Z' | '0' ... '9' | '_' | '.' | '$' => result.push(c), _ => { result.push('$'); for c in c.escape_unicode().skip(1) { match c { '{' => {}, '}' => result.push('$'), c => result.push(c), } } } } } // Underscore-qualify anything that didn't start as an ident. if result.len() > 0 && result.as_bytes()[0] != '_' as u8 && ! (result.as_bytes()[0] as char).is_xid_start() { return format!("_{}", &result[]); } return result; } pub fn mangle>(path: PI, hash: Option<&str>) -> String { // Follow C++ namespace-mangling style, see // http://en.wikipedia.org/wiki/Name_mangling for more info. // // It turns out that on OSX you can actually have arbitrary symbols in // function names (at least when given to LLVM), but this is not possible // when using unix's linker. Perhaps one day when we just use a linker from LLVM // we won't need to do this name mangling. The problem with name mangling is // that it seriously limits the available characters. For example we can't // have things like &T or ~[T] in symbol names when one would theoretically // want them for things like impls of traits on that type. // // To be able to work on all platforms and get *some* reasonable output, we // use C++ name-mangling. let mut n = String::from_str("_ZN"); // _Z == Begin name-sequence, N == nested fn push(n: &mut String, s: &str) { let sani = sanitize(s); n.push_str(&format!("{}{}", sani.len(), sani)[]); } // First, connect each component with pairs. for e in path { push(&mut n, &token::get_name(e.name())) } match hash { Some(s) => push(&mut n, s), None => {} } n.push('E'); // End name-sequence. n } pub fn exported_name(path: PathElems, hash: &str) -> String { mangle(path, Some(hash)) } pub fn mangle_exported_name<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, path: PathElems, t: Ty<'tcx>, id: ast::NodeId) -> String { let mut hash = get_symbol_hash(ccx, t); // Paths can be completely identical for different nodes, // e.g. `fn foo() { { fn a() {} } { fn a() {} } }`, so we // generate unique characters from the node id. For now // hopefully 3 characters is enough to avoid collisions. static EXTRA_CHARS: &'static str = "abcdefghijklmnopqrstuvwxyz\ ABCDEFGHIJKLMNOPQRSTUVWXYZ\ 0123456789"; let id = id as uint; let extra1 = id % EXTRA_CHARS.len(); let id = id / EXTRA_CHARS.len(); let extra2 = id % EXTRA_CHARS.len(); let id = id / EXTRA_CHARS.len(); let extra3 = id % EXTRA_CHARS.len(); hash.push(EXTRA_CHARS.as_bytes()[extra1] as char); hash.push(EXTRA_CHARS.as_bytes()[extra2] as char); hash.push(EXTRA_CHARS.as_bytes()[extra3] as char); exported_name(path, &hash[]) } pub fn mangle_internal_name_by_type_and_seq<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, t: Ty<'tcx>, name: &str) -> String { let s = ppaux::ty_to_string(ccx.tcx(), t); let path = [PathName(token::intern(&s[])), gensym_name(name)]; let hash = get_symbol_hash(ccx, t); mangle(path.iter().cloned(), Some(&hash[])) } pub fn mangle_internal_name_by_path_and_seq(path: PathElems, flav: &str) -> String { mangle(path.chain(Some(gensym_name(flav)).into_iter()), None) } pub fn get_cc_prog(sess: &Session) -> String { match sess.opts.cg.linker { Some(ref linker) => return linker.to_string(), None => sess.target.target.options.linker.clone(), } } pub fn remove(sess: &Session, path: &Path) { match fs::unlink(path) { Ok(..) => {} Err(e) => { sess.err(&format!("failed to remove {}: {}", path.display(), e)[]); } } } /// Perform the linkage portion of the compilation phase. This will generate all /// of the requested outputs for this compilation session. pub fn link_binary(sess: &Session, trans: &CrateTranslation, outputs: &OutputFilenames, crate_name: &str) -> Vec { let mut out_filenames = Vec::new(); for &crate_type in &*sess.crate_types.borrow() { if invalid_output_for_target(sess, crate_type) { sess.bug(&format!("invalid output type `{:?}` for target os `{}`", crate_type, sess.opts.target_triple)[]); } let out_file = link_binary_output(sess, trans, crate_type, outputs, crate_name); out_filenames.push(out_file); } // Remove the temporary object file and metadata if we aren't saving temps if !sess.opts.cg.save_temps { let obj_filename = outputs.temp_path(OutputTypeObject); if !sess.opts.output_types.contains(&OutputTypeObject) { remove(sess, &obj_filename); } remove(sess, &obj_filename.with_extension("metadata.o")); } out_filenames } /// Returns default crate type for target /// /// Default crate type is used when crate type isn't provided neither /// through cmd line arguments nor through crate attributes /// /// It is CrateTypeExecutable for all platforms but iOS as there is no /// way to run iOS binaries anyway without jailbreaking and /// interaction with Rust code through static library is the only /// option for now pub fn default_output_for_target(sess: &Session) -> config::CrateType { if !sess.target.target.options.executables { config::CrateTypeStaticlib } else { config::CrateTypeExecutable } } /// Checks if target supports crate_type as output pub fn invalid_output_for_target(sess: &Session, crate_type: config::CrateType) -> bool { match (sess.target.target.options.dynamic_linking, sess.target.target.options.executables, crate_type) { (false, _, config::CrateTypeDylib) => true, (_, false, config::CrateTypeExecutable) => true, _ => false } } fn is_writeable(p: &Path) -> bool { match p.stat() { Err(..) => true, Ok(m) => m.perm & old_io::USER_WRITE == old_io::USER_WRITE } } pub fn filename_for_input(sess: &Session, crate_type: config::CrateType, name: &str, out_filename: &Path) -> Path { let libname = format!("{}{}", name, sess.opts.cg.extra_filename); match crate_type { config::CrateTypeRlib => { out_filename.with_filename(format!("lib{}.rlib", libname)) } config::CrateTypeDylib => { let (prefix, suffix) = (&sess.target.target.options.dll_prefix[], &sess.target.target.options.dll_suffix[]); out_filename.with_filename(format!("{}{}{}", prefix, libname, suffix)) } config::CrateTypeStaticlib => { out_filename.with_filename(format!("lib{}.a", libname)) } config::CrateTypeExecutable => { let suffix = &sess.target.target.options.exe_suffix[]; out_filename.with_filename(format!("{}{}", libname, suffix)) } } } fn link_binary_output(sess: &Session, trans: &CrateTranslation, crate_type: config::CrateType, outputs: &OutputFilenames, crate_name: &str) -> Path { let obj_filename = outputs.temp_path(OutputTypeObject); let out_filename = match outputs.single_output_file { Some(ref file) => file.clone(), None => { let out_filename = outputs.path(OutputTypeExe); filename_for_input(sess, crate_type, crate_name, &out_filename) } }; // Make sure the output and obj_filename are both writeable. // Mac, FreeBSD, and Windows system linkers check this already -- // however, the Linux linker will happily overwrite a read-only file. // We should be consistent. let obj_is_writeable = is_writeable(&obj_filename); let out_is_writeable = is_writeable(&out_filename); if !out_is_writeable { sess.fatal(&format!("output file {} is not writeable -- check its \ permissions.", out_filename.display())[]); } else if !obj_is_writeable { sess.fatal(&format!("object file {} is not writeable -- check its \ permissions.", obj_filename.display())[]); } match crate_type { config::CrateTypeRlib => { link_rlib(sess, Some(trans), &obj_filename, &out_filename).build(); } config::CrateTypeStaticlib => { link_staticlib(sess, &obj_filename, &out_filename); } config::CrateTypeExecutable => { link_natively(sess, trans, false, &obj_filename, &out_filename); } config::CrateTypeDylib => { link_natively(sess, trans, true, &obj_filename, &out_filename); } } out_filename } fn archive_search_paths(sess: &Session) -> Vec { let mut search = Vec::new(); sess.target_filesearch(PathKind::Native).for_each_lib_search_path(|path, _| { search.push(path.clone()); FileDoesntMatch }); return search; } // Create an 'rlib' // // An rlib in its current incarnation is essentially a renamed .a file. The // rlib primarily contains the object file of the crate, but it also contains // all of the object files from native libraries. This is done by unzipping // native libraries and inserting all of the contents into this archive. fn link_rlib<'a>(sess: &'a Session, trans: Option<&CrateTranslation>, // None == no metadata/bytecode obj_filename: &Path, out_filename: &Path) -> ArchiveBuilder<'a> { let handler = &sess.diagnostic().handler; let config = ArchiveConfig { handler: handler, dst: out_filename.clone(), lib_search_paths: archive_search_paths(sess), slib_prefix: sess.target.target.options.staticlib_prefix.clone(), slib_suffix: sess.target.target.options.staticlib_suffix.clone(), maybe_ar_prog: sess.opts.cg.ar.clone() }; let mut ab = ArchiveBuilder::create(config); ab.add_file(obj_filename).unwrap(); for &(ref l, kind) in &*sess.cstore.get_used_libraries().borrow() { match kind { cstore::NativeStatic => { ab.add_native_library(&l[]).unwrap(); } cstore::NativeFramework | cstore::NativeUnknown => {} } } // After adding all files to the archive, we need to update the // symbol table of the archive. ab.update_symbols(); let mut ab = match sess.target.target.options.is_like_osx { // For OSX/iOS, we must be careful to update symbols only when adding // object files. We're about to start adding non-object files, so run // `ar` now to process the object files. true => ab.build().extend(), false => ab, }; // Note that it is important that we add all of our non-object "magical // files" *after* all of the object files in the archive. The reason for // this is as follows: // // * When performing LTO, this archive will be modified to remove // obj_filename from above. The reason for this is described below. // // * When the system linker looks at an archive, it will attempt to // determine the architecture of the archive in order to see whether its // linkable. // // The algorithm for this detection is: iterate over the files in the // archive. Skip magical SYMDEF names. Interpret the first file as an // object file. Read architecture from the object file. // // * As one can probably see, if "metadata" and "foo.bc" were placed // before all of the objects, then the architecture of this archive would // not be correctly inferred once 'foo.o' is removed. // // Basically, all this means is that this code should not move above the // code above. match trans { Some(trans) => { // Instead of putting the metadata in an object file section, rlibs // contain the metadata in a separate file. We use a temp directory // here so concurrent builds in the same directory don't try to use // the same filename for metadata (stomping over one another) let tmpdir = TempDir::new("rustc").ok().expect("needs a temp dir"); let metadata = tmpdir.path().join(METADATA_FILENAME); match fs::File::create(&metadata).write_all(&trans.metadata[]) { Ok(..) => {} Err(e) => { sess.err(&format!("failed to write {}: {}", metadata.display(), e)[]); sess.abort_if_errors(); } } ab.add_file(&metadata).unwrap(); remove(sess, &metadata); // For LTO purposes, the bytecode of this library is also inserted // into the archive. If codegen_units > 1, we insert each of the // bitcode files. for i in 0..sess.opts.cg.codegen_units { // Note that we make sure that the bytecode filename in the // archive is never exactly 16 bytes long by adding a 16 byte // extension to it. This is to work around a bug in LLDB that // would cause it to crash if the name of a file in an archive // was exactly 16 bytes. let bc_filename = obj_filename.with_extension(&format!("{}.bc", i)); let bc_deflated_filename = obj_filename.with_extension( &format!("{}.bytecode.deflate", i)[]); let bc_data = match fs::File::open(&bc_filename).read_to_end() { Ok(buffer) => buffer, Err(e) => sess.fatal(&format!("failed to read bytecode: {}", e)[]) }; let bc_data_deflated = match flate::deflate_bytes(&bc_data[]) { Some(compressed) => compressed, None => sess.fatal(&format!("failed to compress bytecode from {}", bc_filename.display())[]) }; let mut bc_file_deflated = match fs::File::create(&bc_deflated_filename) { Ok(file) => file, Err(e) => { sess.fatal(&format!("failed to create compressed bytecode \ file: {}", e)[]) } }; match write_rlib_bytecode_object_v1(&mut bc_file_deflated, bc_data_deflated.as_slice()) { Ok(()) => {} Err(e) => { sess.err(&format!("failed to write compressed bytecode: \ {}", e)[]); sess.abort_if_errors() } }; ab.add_file(&bc_deflated_filename).unwrap(); remove(sess, &bc_deflated_filename); // See the bottom of back::write::run_passes for an explanation // of when we do and don't keep .0.bc files around. let user_wants_numbered_bitcode = sess.opts.output_types.contains(&OutputTypeBitcode) && sess.opts.cg.codegen_units > 1; if !sess.opts.cg.save_temps && !user_wants_numbered_bitcode { remove(sess, &bc_filename); } } // After adding all files to the archive, we need to update the // symbol table of the archive. This currently dies on OSX (see // #11162), and isn't necessary there anyway if !sess.target.target.options.is_like_osx { ab.update_symbols(); } } None => {} } ab } fn write_rlib_bytecode_object_v1(writer: &mut T, bc_data_deflated: &[u8]) -> ::std::old_io::IoResult<()> { let bc_data_deflated_size: u64 = bc_data_deflated.len() as u64; try! { writer.write_all(RLIB_BYTECODE_OBJECT_MAGIC) }; try! { writer.write_le_u32(1) }; try! { writer.write_le_u64(bc_data_deflated_size) }; try! { writer.write_all(&bc_data_deflated[]) }; let number_of_bytes_written_so_far = RLIB_BYTECODE_OBJECT_MAGIC.len() + // magic id mem::size_of_val(&RLIB_BYTECODE_OBJECT_VERSION) + // version mem::size_of_val(&bc_data_deflated_size) + // data size field bc_data_deflated_size as uint; // actual data // If the number of bytes written to the object so far is odd, add a // padding byte to make it even. This works around a crash bug in LLDB // (see issue #15950) if number_of_bytes_written_so_far % 2 == 1 { try! { writer.write_u8(0) }; } return Ok(()); } // Create a static archive // // This is essentially the same thing as an rlib, but it also involves adding // all of the upstream crates' objects into the archive. This will slurp in // all of the native libraries of upstream dependencies as well. // // Additionally, there's no way for us to link dynamic libraries, so we warn // about all dynamic library dependencies that they're not linked in. // // There's no need to include metadata in a static archive, so ensure to not // link in the metadata object file (and also don't prepare the archive with a // metadata file). fn link_staticlib(sess: &Session, obj_filename: &Path, out_filename: &Path) { let ab = link_rlib(sess, None, obj_filename, out_filename); let mut ab = match sess.target.target.options.is_like_osx { true => ab.build().extend(), false => ab, }; if sess.target.target.options.morestack { ab.add_native_library("morestack").unwrap(); } if !sess.target.target.options.no_compiler_rt { ab.add_native_library("compiler-rt").unwrap(); } let crates = sess.cstore.get_used_crates(cstore::RequireStatic); let mut all_native_libs = vec![]; for &(cnum, ref path) in &crates { let ref name = sess.cstore.get_crate_data(cnum).name; let p = match *path { Some(ref p) => p.clone(), None => { sess.err(&format!("could not find rlib for: `{}`", name)[]); continue } }; ab.add_rlib(&p, &name[], sess.lto()).unwrap(); let native_libs = csearch::get_native_libraries(&sess.cstore, cnum); all_native_libs.extend(native_libs.into_iter()); } ab.update_symbols(); let _ = ab.build(); if !all_native_libs.is_empty() { sess.note("link against the following native artifacts when linking against \ this static library"); sess.note("the order and any duplication can be significant on some platforms, \ and so may need to be preserved"); } for &(kind, ref lib) in &all_native_libs { let name = match kind { cstore::NativeStatic => "static library", cstore::NativeUnknown => "library", cstore::NativeFramework => "framework", }; sess.note(&format!("{}: {}", name, *lib)[]); } } // Create a dynamic library or executable // // This will invoke the system linker/cc to create the resulting file. This // links to all upstream files as well. fn link_natively(sess: &Session, trans: &CrateTranslation, dylib: bool, obj_filename: &Path, out_filename: &Path) { let tmpdir = TempDir::new("rustc").ok().expect("needs a temp dir"); // The invocations of cc share some flags across platforms let pname = get_cc_prog(sess); let mut cmd = Command::new(&pname[]); cmd.args(&sess.target.target.options.pre_link_args[]); link_args(&mut cmd, sess, dylib, tmpdir.path(), trans, obj_filename, out_filename); cmd.args(&sess.target.target.options.post_link_args[]); if !sess.target.target.options.no_compiler_rt { cmd.arg("-lcompiler-rt"); } if sess.opts.debugging_opts.print_link_args { println!("{:?}", &cmd); } // May have not found libraries in the right formats. sess.abort_if_errors(); // Invoke the system linker debug!("{:?}", &cmd); let prog = time(sess.time_passes(), "running linker", (), |()| cmd.output()); match prog { Ok(prog) => { if !prog.status.success() { sess.err(&format!("linking with `{}` failed: {}", pname, prog.status)[]); sess.note(&format!("{:?}", &cmd)[]); let mut output = prog.error.clone(); output.push_all(&prog.output[]); sess.note(str::from_utf8(&output[]).unwrap()); sess.abort_if_errors(); } debug!("linker stderr:\n{}", String::from_utf8(prog.error).unwrap()); debug!("linker stdout:\n{}", String::from_utf8(prog.output).unwrap()); }, Err(e) => { sess.err(&format!("could not exec the linker `{}`: {}", pname, e)[]); sess.abort_if_errors(); } } // On OSX, debuggers need this utility to get run to do some munging of // the symbols if sess.target.target.options.is_like_osx && sess.opts.debuginfo != NoDebugInfo { match Command::new("dsymutil").arg(out_filename).output() { Ok(..) => {} Err(e) => { sess.err(&format!("failed to run dsymutil: {}", e)[]); sess.abort_if_errors(); } } } } fn link_args(cmd: &mut Command, sess: &Session, dylib: bool, tmpdir: &Path, trans: &CrateTranslation, obj_filename: &Path, out_filename: &Path) { // The default library location, we need this to find the runtime. // The location of crates will be determined as needed. let lib_path = sess.target_filesearch(PathKind::All).get_lib_path(); // target descriptor let t = &sess.target.target; cmd.arg("-L").arg(&lib_path); cmd.arg("-o").arg(out_filename).arg(obj_filename); // Stack growth requires statically linking a __morestack function. Note // that this is listed *before* all other libraries. Due to the usage of the // --as-needed flag below, the standard library may only be useful for its // rust_stack_exhausted function. In this case, we must ensure that the // libmorestack.a file appears *before* the standard library (so we put it // at the very front). // // Most of the time this is sufficient, except for when LLVM gets super // clever. If, for example, we have a main function `fn main() {}`, LLVM // will optimize out calls to `__morestack` entirely because the function // doesn't need any stack at all! // // To get around this snag, we specially tell the linker to always include // all contents of this library. This way we're guaranteed that the linker // will include the __morestack symbol 100% of the time, always resolving // references to it even if the object above didn't use it. if t.options.morestack { if t.options.is_like_osx { let morestack = lib_path.join("libmorestack.a"); let mut v = b"-Wl,-force_load,".to_vec(); v.push_all(morestack.as_vec()); cmd.arg(&v[]); } else { cmd.args(&["-Wl,--whole-archive", "-lmorestack", "-Wl,--no-whole-archive"]); } } // When linking a dynamic library, we put the metadata into a section of the // executable. This metadata is in a separate object file from the main // object file, so we link that in here. if dylib { cmd.arg(obj_filename.with_extension("metadata.o")); } if t.options.is_like_osx { // The dead_strip option to the linker specifies that functions and data // unreachable by the entry point will be removed. This is quite useful // with Rust's compilation model of compiling libraries at a time into // one object file. For example, this brings hello world from 1.7MB to // 458K. // // Note that this is done for both executables and dynamic libraries. We // won't get much benefit from dylibs because LLVM will have already // stripped away as much as it could. This has not been seen to impact // link times negatively. // // -dead_strip can't be part of the pre_link_args because it's also used for partial // linking when using multiple codegen units (-r). So we insert it here. cmd.arg("-Wl,-dead_strip"); } // If we're building a dylib, we don't use --gc-sections because LLVM has // already done the best it can do, and we also don't want to eliminate the // metadata. If we're building an executable, however, --gc-sections drops // the size of hello world from 1.8MB to 597K, a 67% reduction. if !dylib && !t.options.is_like_osx { cmd.arg("-Wl,--gc-sections"); } let used_link_args = sess.cstore.get_used_link_args().borrow(); if t.options.position_independent_executables { let empty_vec = Vec::new(); let empty_str = String::new(); let args = sess.opts.cg.link_args.as_ref().unwrap_or(&empty_vec); let mut args = args.iter().chain(used_link_args.iter()); if !dylib && (t.options.relocation_model == "pic" || *sess.opts.cg.relocation_model.as_ref() .unwrap_or(&empty_str) == "pic") && !args.any(|x| *x == "-static") { cmd.arg("-pie"); } } if t.options.linker_is_gnu { // GNU-style linkers support optimization with -O. GNU ld doesn't need a // numeric argument, but other linkers do. if sess.opts.optimize == config::Default || sess.opts.optimize == config::Aggressive { cmd.arg("-Wl,-O1"); } } // We want to prevent the compiler from accidentally leaking in any system // libraries, so we explicitly ask gcc to not link to any libraries by // default. Note that this does not happen for windows because windows pulls // in some large number of libraries and I couldn't quite figure out which // subset we wanted. if !t.options.is_like_windows { cmd.arg("-nodefaultlibs"); } // Mark all dynamic libraries and executables as compatible with ASLR // FIXME #17098: ASLR breaks gdb if t.options.is_like_windows && sess.opts.debuginfo == NoDebugInfo { // cmd.arg("-Wl,--dynamicbase"); } // Take careful note of the ordering of the arguments we pass to the linker // here. Linkers will assume that things on the left depend on things to the // right. Things on the right cannot depend on things on the left. This is // all formally implemented in terms of resolving symbols (libs on the right // resolve unknown symbols of libs on the left, but not vice versa). // // For this reason, we have organized the arguments we pass to the linker as // such: // // 1. The local object that LLVM just generated // 2. Upstream rust libraries // 3. Local native libraries // 4. Upstream native libraries // // This is generally fairly natural, but some may expect 2 and 3 to be // swapped. The reason that all native libraries are put last is that it's // not recommended for a native library to depend on a symbol from a rust // crate. If this is the case then a staticlib crate is recommended, solving // the problem. // // Additionally, it is occasionally the case that upstream rust libraries // depend on a local native library. In the case of libraries such as // lua/glfw/etc the name of the library isn't the same across all platforms, // so only the consumer crate of a library knows the actual name. This means // that downstream crates will provide the #[link] attribute which upstream // crates will depend on. Hence local native libraries are after out // upstream rust crates. // // In theory this means that a symbol in an upstream native library will be // shadowed by a local native library when it wouldn't have been before, but // this kind of behavior is pretty platform specific and generally not // recommended anyway, so I don't think we're shooting ourself in the foot // much with that. add_upstream_rust_crates(cmd, sess, dylib, tmpdir, trans); add_local_native_libraries(cmd, sess); add_upstream_native_libraries(cmd, sess); // # Telling the linker what we're doing if dylib { // On mac we need to tell the linker to let this library be rpathed if sess.target.target.options.is_like_osx { cmd.args(&["-dynamiclib", "-Wl,-dylib"]); if sess.opts.cg.rpath { let mut v = "-Wl,-install_name,@rpath/".as_bytes().to_vec(); v.push_all(out_filename.filename().unwrap()); cmd.arg(&v[]); } } else { cmd.arg("-shared"); } } // FIXME (#2397): At some point we want to rpath our guesses as to // where extern libraries might live, based on the // addl_lib_search_paths if sess.opts.cg.rpath { let sysroot = sess.sysroot(); let target_triple = &sess.opts.target_triple[]; let get_install_prefix_lib_path = || { let install_prefix = option_env!("CFG_PREFIX").expect("CFG_PREFIX"); let tlib = filesearch::relative_target_lib_path(sysroot, target_triple); let mut path = Path::new(install_prefix); path.push(&tlib); path }; let rpath_config = RPathConfig { used_crates: sess.cstore.get_used_crates(cstore::RequireDynamic), out_filename: out_filename.clone(), has_rpath: sess.target.target.options.has_rpath, is_like_osx: sess.target.target.options.is_like_osx, get_install_prefix_lib_path: get_install_prefix_lib_path, realpath: ::util::fs::realpath }; cmd.args(&rpath::get_rpath_flags(rpath_config)[]); } // Finally add all the linker arguments provided on the command line along // with any #[link_args] attributes found inside the crate let empty = Vec::new(); cmd.args(&sess.opts.cg.link_args.as_ref().unwrap_or(&empty)[]); cmd.args(&used_link_args[]); } // # Native library linking // // User-supplied library search paths (-L on the command line). These are // the same paths used to find Rust crates, so some of them may have been // added already by the previous crate linking code. This only allows them // to be found at compile time so it is still entirely up to outside // forces to make sure that library can be found at runtime. // // Also note that the native libraries linked here are only the ones located // in the current crate. Upstream crates with native library dependencies // may have their native library pulled in above. fn add_local_native_libraries(cmd: &mut Command, sess: &Session) { sess.target_filesearch(PathKind::All).for_each_lib_search_path(|path, k| { match k { PathKind::Framework => { cmd.arg("-F").arg(path); } _ => { cmd.arg("-L").arg(path); } } FileDoesntMatch }); // Some platforms take hints about whether a library is static or dynamic. // For those that support this, we ensure we pass the option if the library // was flagged "static" (most defaults are dynamic) to ensure that if // libfoo.a and libfoo.so both exist that the right one is chosen. let takes_hints = !sess.target.target.options.is_like_osx; let libs = sess.cstore.get_used_libraries(); let libs = libs.borrow(); let staticlibs = libs.iter().filter_map(|&(ref l, kind)| { if kind == cstore::NativeStatic {Some(l)} else {None} }); let others = libs.iter().filter(|&&(_, kind)| { kind != cstore::NativeStatic }); // Platforms that take hints generally also support the --whole-archive // flag. We need to pass this flag when linking static native libraries to // ensure the entire library is included. // // For more details see #15460, but the gist is that the linker will strip // away any unused objects in the archive if we don't otherwise explicitly // reference them. This can occur for libraries which are just providing // bindings, libraries with generic functions, etc. if takes_hints { cmd.arg("-Wl,--whole-archive").arg("-Wl,-Bstatic"); } let search_path = archive_search_paths(sess); for l in staticlibs { if takes_hints { cmd.arg(format!("-l{}", l)); } else { // -force_load is the OSX equivalent of --whole-archive, but it // involves passing the full path to the library to link. let lib = archive::find_library(&l[], &sess.target.target.options.staticlib_prefix, &sess.target.target.options.staticlib_suffix, &search_path[], &sess.diagnostic().handler); let mut v = b"-Wl,-force_load,".to_vec(); v.push_all(lib.as_vec()); cmd.arg(&v[]); } } if takes_hints { cmd.arg("-Wl,--no-whole-archive").arg("-Wl,-Bdynamic"); } for &(ref l, kind) in others { match kind { cstore::NativeUnknown => { cmd.arg(format!("-l{}", l)); } cstore::NativeFramework => { cmd.arg("-framework").arg(&l[]); } cstore::NativeStatic => unreachable!(), } } } // # Rust Crate linking // // Rust crates are not considered at all when creating an rlib output. All // dependencies will be linked when producing the final output (instead of // the intermediate rlib version) fn add_upstream_rust_crates(cmd: &mut Command, sess: &Session, dylib: bool, tmpdir: &Path, trans: &CrateTranslation) { // All of the heavy lifting has previously been accomplished by the // dependency_format module of the compiler. This is just crawling the // output of that module, adding crates as necessary. // // Linking to a rlib involves just passing it to the linker (the linker // will slurp up the object files inside), and linking to a dynamic library // involves just passing the right -l flag. let data = if dylib { &trans.crate_formats[config::CrateTypeDylib] } else { &trans.crate_formats[config::CrateTypeExecutable] }; // Invoke get_used_crates to ensure that we get a topological sorting of // crates. let deps = sess.cstore.get_used_crates(cstore::RequireDynamic); for &(cnum, _) in &deps { // 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. let kind = match data[cnum as uint - 1] { Some(t) => t, None => continue }; let src = sess.cstore.get_used_crate_source(cnum).unwrap(); match kind { cstore::RequireDynamic => { add_dynamic_crate(cmd, sess, src.dylib.unwrap().0) } cstore::RequireStatic => { add_static_crate(cmd, sess, tmpdir, src.rlib.unwrap().0) } } } // Converts a library file-stem into a cc -l argument fn unlib<'a>(config: &config::Config, stem: &'a [u8]) -> &'a [u8] { if stem.starts_with("lib".as_bytes()) && !config.target.options.is_like_windows { &stem[3..] } else { stem } } // Adds the static "rlib" versions of all crates to the command line. fn add_static_crate(cmd: &mut Command, sess: &Session, tmpdir: &Path, cratepath: Path) { // When performing LTO on an executable output, all of the // bytecode from the upstream libraries has already been // included in our object file output. We need to modify all of // the upstream archives to remove their corresponding object // file to make sure we don't pull the same code in twice. // // We must continue to link to the upstream archives to be sure // to pull in native static dependencies. As the final caveat, // on Linux it is apparently illegal to link to a blank archive, // so if an archive no longer has any object files in it after // we remove `lib.o`, then don't link against it at all. // // If we're not doing LTO, then our job is simply to just link // against the archive. if sess.lto() { let name = cratepath.filename_str().unwrap(); let name = &name[3..name.len() - 5]; // chop off lib/.rlib time(sess.time_passes(), &format!("altering {}.rlib", name)[], (), |()| { let dst = tmpdir.join(cratepath.filename().unwrap()); match fs::copy(&cratepath, &dst) { Ok(..) => {} Err(e) => { sess.err(&format!("failed to copy {} to {}: {}", cratepath.display(), dst.display(), e)[]); sess.abort_if_errors(); } } // Fix up permissions of the copy, as fs::copy() preserves // permissions, but the original file may have been installed // by a package manager and may be read-only. match fs::chmod(&dst, old_io::USER_READ | old_io::USER_WRITE) { Ok(..) => {} Err(e) => { sess.err(&format!("failed to chmod {} when preparing \ for LTO: {}", dst.display(), e)[]); sess.abort_if_errors(); } } let handler = &sess.diagnostic().handler; let config = ArchiveConfig { handler: handler, dst: dst.clone(), lib_search_paths: archive_search_paths(sess), slib_prefix: sess.target.target.options.staticlib_prefix.clone(), slib_suffix: sess.target.target.options.staticlib_suffix.clone(), maybe_ar_prog: sess.opts.cg.ar.clone() }; let mut archive = Archive::open(config); archive.remove_file(&format!("{}.o", name)[]); let files = archive.files(); if files.iter().any(|s| s[].ends_with(".o")) { cmd.arg(dst); } }); } else { cmd.arg(cratepath); } } // Same thing as above, but for dynamic crates instead of static crates. fn add_dynamic_crate(cmd: &mut Command, sess: &Session, cratepath: Path) { // If we're performing LTO, then it should have been previously required // that all upstream rust dependencies were available in an rlib format. assert!(!sess.lto()); // Just need to tell the linker about where the library lives and // what its name is let dir = cratepath.dirname(); if !dir.is_empty() { cmd.arg("-L").arg(dir); } let mut v = "-l".as_bytes().to_vec(); v.push_all(unlib(&sess.target, cratepath.filestem().unwrap())); cmd.arg(&v[]); } } // Link in all of our upstream crates' native dependencies. Remember that // all of these upstream native dependencies are all non-static // dependencies. We've got two cases then: // // 1. The upstream crate is an rlib. In this case we *must* link in the // native dependency because the rlib is just an archive. // // 2. The upstream crate is a dylib. In order to use the dylib, we have to // have the dependency present on the system somewhere. Thus, we don't // gain a whole lot from not linking in the dynamic dependency to this // crate as well. // // The use case for this is a little subtle. In theory the native // dependencies of a crate are purely an implementation detail of the crate // itself, but the problem arises with generic and inlined functions. If a // generic function calls a native function, then the generic function must // be instantiated in the target crate, meaning that the native symbol must // also be resolved in the target crate. fn add_upstream_native_libraries(cmd: &mut Command, sess: &Session) { // Be sure to use a topological sorting of crates because there may be // interdependencies between native libraries. When passing -nodefaultlibs, // for example, almost all native libraries depend on libc, so we have to // make sure that's all the way at the right (liblibc is near the base of // the dependency chain). // // This passes RequireStatic, but the actual requirement doesn't matter, // we're just getting an ordering of crate numbers, we're not worried about // the paths. let crates = sess.cstore.get_used_crates(cstore::RequireStatic); for (cnum, _) in crates { let libs = csearch::get_native_libraries(&sess.cstore, cnum); for &(kind, ref lib) in &libs { match kind { cstore::NativeUnknown => { cmd.arg(format!("-l{}", *lib)); } cstore::NativeFramework => { cmd.arg("-framework"); cmd.arg(&lib[]); } cstore::NativeStatic => { sess.bug("statics shouldn't be propagated"); } } } } }