/
linker.rs
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/
linker.rs
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// Copyright 2015 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 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use std::env;
use std::ffi::OsString;
use std::fs::{self, File};
use std::io::{self, BufWriter};
use std::io::prelude::*;
use std::path::{Path, PathBuf};
use std::process::Command;
use back::archive;
use middle::cstore::CrateStore;
use middle::dependency_format::Linkage;
use session::Session;
use session::config::CrateTypeDylib;
use session::config;
use syntax::ast;
use trans::CrateTranslation;
/// Linker abstraction used by back::link to build up the command to invoke a
/// linker.
///
/// This trait is the total list of requirements needed by `back::link` and
/// represents the meaning of each option being passed down. This trait is then
/// used to dispatch on whether a GNU-like linker (generally `ld.exe`) or an
/// MSVC linker (e.g. `link.exe`) is being used.
pub trait Linker {
fn link_dylib(&mut self, lib: &str);
fn link_rust_dylib(&mut self, lib: &str, path: &Path);
fn link_framework(&mut self, framework: &str);
fn link_staticlib(&mut self, lib: &str);
fn link_rlib(&mut self, lib: &Path);
fn link_whole_rlib(&mut self, lib: &Path);
fn link_whole_staticlib(&mut self, lib: &str, search_path: &[PathBuf]);
fn include_path(&mut self, path: &Path);
fn framework_path(&mut self, path: &Path);
fn output_filename(&mut self, path: &Path);
fn add_object(&mut self, path: &Path);
fn gc_sections(&mut self, is_dylib: bool);
fn position_independent_executable(&mut self);
fn optimize(&mut self);
fn debuginfo(&mut self);
fn no_default_libraries(&mut self);
fn build_dylib(&mut self, out_filename: &Path);
fn args(&mut self, args: &[String]);
fn hint_static(&mut self);
fn hint_dynamic(&mut self);
fn whole_archives(&mut self);
fn no_whole_archives(&mut self);
fn export_symbols(&mut self, sess: &Session, trans: &CrateTranslation,
tmpdir: &Path);
fn try_gold_linker(&mut self);
}
pub struct GnuLinker<'a> {
pub cmd: &'a mut Command,
pub sess: &'a Session,
}
impl<'a> GnuLinker<'a> {
fn takes_hints(&self) -> bool {
!self.sess.target.target.options.is_like_osx
}
}
impl<'a> Linker for GnuLinker<'a> {
fn link_dylib(&mut self, lib: &str) { self.cmd.arg("-l").arg(lib); }
fn link_staticlib(&mut self, lib: &str) { self.cmd.arg("-l").arg(lib); }
fn link_rlib(&mut self, lib: &Path) { self.cmd.arg(lib); }
fn include_path(&mut self, path: &Path) { self.cmd.arg("-L").arg(path); }
fn framework_path(&mut self, path: &Path) { self.cmd.arg("-F").arg(path); }
fn output_filename(&mut self, path: &Path) { self.cmd.arg("-o").arg(path); }
fn add_object(&mut self, path: &Path) { self.cmd.arg(path); }
fn position_independent_executable(&mut self) { self.cmd.arg("-pie"); }
fn args(&mut self, args: &[String]) { self.cmd.args(args); }
fn link_rust_dylib(&mut self, lib: &str, _path: &Path) {
self.cmd.arg("-l").arg(lib);
}
fn link_framework(&mut self, framework: &str) {
self.cmd.arg("-framework").arg(framework);
}
fn link_whole_staticlib(&mut self, lib: &str, search_path: &[PathBuf]) {
let target = &self.sess.target.target;
if !target.options.is_like_osx {
self.cmd.arg("-Wl,--whole-archive")
.arg("-l").arg(lib)
.arg("-Wl,--no-whole-archive");
} else {
// -force_load is the OSX equivalent of --whole-archive, but it
// involves passing the full path to the library to link.
let mut v = OsString::from("-Wl,-force_load,");
v.push(&archive::find_library(lib, search_path, &self.sess));
self.cmd.arg(&v);
}
}
fn link_whole_rlib(&mut self, lib: &Path) {
if self.sess.target.target.options.is_like_osx {
let mut v = OsString::from("-Wl,-force_load,");
v.push(lib);
self.cmd.arg(&v);
} else {
self.cmd.arg("-Wl,--whole-archive").arg(lib)
.arg("-Wl,--no-whole-archive");
}
}
fn gc_sections(&mut self, is_dylib: bool) {
// 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.
if self.sess.target.target.options.is_like_osx {
self.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.
} else if !is_dylib {
self.cmd.arg("-Wl,--gc-sections");
}
}
fn optimize(&mut self) {
if !self.sess.target.target.options.linker_is_gnu { return }
// GNU-style linkers support optimization with -O. GNU ld doesn't
// need a numeric argument, but other linkers do.
if self.sess.opts.optimize == config::Default ||
self.sess.opts.optimize == config::Aggressive {
self.cmd.arg("-Wl,-O1");
}
}
fn debuginfo(&mut self) {
// Don't do anything special here for GNU-style linkers.
}
fn no_default_libraries(&mut self) {
self.cmd.arg("-nodefaultlibs");
}
fn build_dylib(&mut self, out_filename: &Path) {
// On mac we need to tell the linker to let this library be rpathed
if self.sess.target.target.options.is_like_osx {
self.cmd.args(&["-dynamiclib", "-Wl,-dylib"]);
if self.sess.opts.cg.rpath {
let mut v = OsString::from("-Wl,-install_name,@rpath/");
v.push(out_filename.file_name().unwrap());
self.cmd.arg(&v);
}
} else {
self.cmd.arg("-shared");
}
}
fn whole_archives(&mut self) {
if !self.takes_hints() { return }
self.cmd.arg("-Wl,--whole-archive");
}
fn no_whole_archives(&mut self) {
if !self.takes_hints() { return }
self.cmd.arg("-Wl,--no-whole-archive");
}
fn hint_static(&mut self) {
if !self.takes_hints() { return }
self.cmd.arg("-Wl,-Bstatic");
}
fn hint_dynamic(&mut self) {
if !self.takes_hints() { return }
self.cmd.arg("-Wl,-Bdynamic");
}
fn export_symbols(&mut self, _: &Session, _: &CrateTranslation, _: &Path) {
// noop, visibility in object files takes care of this
}
fn try_gold_linker(&mut self) {
// Only use gold under specific conditions that we know work
let gold_exists = match env::var_os("PATH") {
Some(ref env_path) => {
env::split_paths(env_path).any(|mut p| {
p.push("ld.gold");
p.exists()
})
}
None => false
};
let host_is_linux = cfg!(target_os = "linux");
// Defensively prevent trying to use gold for bogus cross-targets.
let target_is_host_compatible = {
let host_os_is_target_os = self.sess.target.target.target_os == env::consts::OS;
let host_arch_is_target_arch = self.sess.target.target.arch == env::consts::ARCH;
// Support x86_64->i686 and reverse
let host_and_target_are_x86ish =
(self.sess.target.target.arch == "x86" ||
self.sess.target.target.arch == "x86_64") &&
(env::consts::ARCH == "x86" ||
env::consts::ARCH == "x86_64");
host_os_is_target_os && (host_arch_is_target_arch || host_and_target_are_x86ish)
};
// We have strong confidence that x86 works, but not much
// visibility into other architectures.
let target_works_with_gold =
self.sess.target.target.arch == "x86" ||
self.sess.target.target.arch == "x86_64";
let opt_out = self.sess.opts.cg.disable_gold;
let can_use_gold =
gold_exists &&
host_is_linux &&
target_is_host_compatible &&
target_works_with_gold &&
!opt_out;
if can_use_gold {
info!("linking with ld.gold");
self.cmd.arg("-fuse-ld=gold");
} else {
info!("linking with ld");
}
}
}
pub struct MsvcLinker<'a> {
pub cmd: &'a mut Command,
pub sess: &'a Session,
}
impl<'a> Linker for MsvcLinker<'a> {
fn link_rlib(&mut self, lib: &Path) { self.cmd.arg(lib); }
fn add_object(&mut self, path: &Path) { self.cmd.arg(path); }
fn args(&mut self, args: &[String]) { self.cmd.args(args); }
fn build_dylib(&mut self, _out_filename: &Path) { self.cmd.arg("/DLL"); }
fn gc_sections(&mut self, _is_dylib: bool) { self.cmd.arg("/OPT:REF,ICF"); }
fn link_dylib(&mut self, lib: &str) {
self.cmd.arg(&format!("{}.lib", lib));
}
fn link_rust_dylib(&mut self, lib: &str, path: &Path) {
// When producing a dll, the MSVC linker may not actually emit a
// `foo.lib` file if the dll doesn't actually export any symbols, so we
// check to see if the file is there and just omit linking to it if it's
// not present.
let name = format!("{}.lib", lib);
if fs::metadata(&path.join(&name)).is_ok() {
self.cmd.arg(name);
}
}
fn link_staticlib(&mut self, lib: &str) {
self.cmd.arg(&format!("{}.lib", lib));
}
fn position_independent_executable(&mut self) {
// noop
}
fn no_default_libraries(&mut self) {
// Currently we don't pass the /NODEFAULTLIB flag to the linker on MSVC
// as there's been trouble in the past of linking the C++ standard
// library required by LLVM. This likely needs to happen one day, but
// in general Windows is also a more controlled environment than
// Unix, so it's not necessarily as critical that this be implemented.
//
// Note that there are also some licensing worries about statically
// linking some libraries which require a specific agreement, so it may
// not ever be possible for us to pass this flag.
}
fn include_path(&mut self, path: &Path) {
let mut arg = OsString::from("/LIBPATH:");
arg.push(path);
self.cmd.arg(&arg);
}
fn output_filename(&mut self, path: &Path) {
let mut arg = OsString::from("/OUT:");
arg.push(path);
self.cmd.arg(&arg);
}
fn framework_path(&mut self, _path: &Path) {
panic!("frameworks are not supported on windows")
}
fn link_framework(&mut self, _framework: &str) {
panic!("frameworks are not supported on windows")
}
fn link_whole_staticlib(&mut self, lib: &str, _search_path: &[PathBuf]) {
// not supported?
self.link_staticlib(lib);
}
fn link_whole_rlib(&mut self, path: &Path) {
// not supported?
self.link_rlib(path);
}
fn optimize(&mut self) {
// Needs more investigation of `/OPT` arguments
}
fn debuginfo(&mut self) {
// This will cause the Microsoft linker to generate a PDB file
// from the CodeView line tables in the object files.
self.cmd.arg("/DEBUG");
}
fn whole_archives(&mut self) {
// hints not supported?
}
fn no_whole_archives(&mut self) {
// hints not supported?
}
// On windows static libraries are of the form `foo.lib` and dynamic
// libraries are not linked against directly, but rather through their
// import libraries also called `foo.lib`. As a result there's no
// possibility for a native library to appear both dynamically and
// statically in the same folder so we don't have to worry about hints like
// we do on Unix platforms.
fn hint_static(&mut self) {}
fn hint_dynamic(&mut self) {}
// Currently the compiler doesn't use `dllexport` (an LLVM attribute) to
// export symbols from a dynamic library. When building a dynamic library,
// however, we're going to want some symbols exported, so this function
// generates a DEF file which lists all the symbols.
//
// The linker will read this `*.def` file and export all the symbols from
// the dynamic library. Note that this is not as simple as just exporting
// all the symbols in the current crate (as specified by `trans.reachable`)
// but rather we also need to possibly export the symbols of upstream
// crates. Upstream rlibs may be linked statically to this dynamic library,
// in which case they may continue to transitively be used and hence need
// their symbols exported.
fn export_symbols(&mut self, sess: &Session, trans: &CrateTranslation,
tmpdir: &Path) {
let path = tmpdir.join("lib.def");
let res = (|| -> io::Result<()> {
let mut f = BufWriter::new(try!(File::create(&path)));
// Start off with the standard module name header and then go
// straight to exports.
try!(writeln!(f, "LIBRARY"));
try!(writeln!(f, "EXPORTS"));
// Write out all our local symbols
for sym in trans.reachable.iter() {
try!(writeln!(f, " {}", sym));
}
// Take a look at how all upstream crates are linked into this
// dynamic library. For all statically linked libraries we take all
// their reachable symbols and emit them as well.
let cstore = &sess.cstore;
let formats = sess.dependency_formats.borrow();
let symbols = formats[&CrateTypeDylib].iter();
let symbols = symbols.enumerate().filter_map(|(i, f)| {
if *f == Linkage::Static {
Some((i + 1) as ast::CrateNum)
} else {
None
}
}).flat_map(|cnum| {
cstore.reachable_ids(cnum)
}).map(|did| {
cstore.item_symbol(did)
});
for symbol in symbols {
try!(writeln!(f, " {}", symbol));
}
Ok(())
})();
if let Err(e) = res {
sess.fatal(&format!("failed to write lib.def file: {}", e));
}
let mut arg = OsString::from("/DEF:");
arg.push(path);
self.cmd.arg(&arg);
}
fn try_gold_linker(&mut self) {}
}