src/librustc_trans/back/linker.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use std::ffi::OsString;
  12 use std::path::{Path, PathBuf};
  13 use std::process::Command;
  14 use std::fs;
  15
  16 use back::archive;
  17 use session::Session;
  18 use session::config;
  19 use session::config::DebugInfoLevel::{NoDebugInfo, LimitedDebugInfo, FullDebugInfo};
  20
  21 /// Linker abstraction used by back::link to build up the command to invoke a
  22 /// linker.
  23 ///
  24 /// This trait is the total list of requirements needed by `back::link` and
  25 /// represents the meaning of each option being passed down. This trait is then
  26 /// used to dispatch on whether a GNU-like linker (generally `ld.exe`) or an
  27 /// MSVC linker (e.g. `link.exe`) is being used.
  28 pub trait Linker {
  29     fn link_dylib(&mut self, lib: &str);
  30     fn link_rust_dylib(&mut self, lib: &str, path: &Path);
  31     fn link_framework(&mut self, framework: &str);
  32     fn link_staticlib(&mut self, lib: &str);
  33     fn link_rlib(&mut self, lib: &Path);
  34     fn link_whole_rlib(&mut self, lib: &Path);
  35     fn link_whole_staticlib(&mut self, lib: &str, search_path: &[PathBuf]);
  36     fn include_path(&mut self, path: &Path);
  37     fn framework_path(&mut self, path: &Path);
  38     fn output_filename(&mut self, path: &Path);
  39     fn add_object(&mut self, path: &Path);
  40     fn gc_sections(&mut self, is_dylib: bool);
  41     fn position_independent_executable(&mut self);
  42     fn optimize(&mut self);
  43     fn debuginfo(&mut self);
  44     fn no_default_libraries(&mut self);
  45     fn build_dylib(&mut self, out_filename: &Path);
  46     fn args(&mut self, args: &[String]);
  47     fn hint_static(&mut self);
  48     fn hint_dynamic(&mut self);
  49     fn whole_archives(&mut self);
  50     fn no_whole_archives(&mut self);
  51 }
  52
  53 pub struct GnuLinker<'a> {
  54     pub cmd: &'a mut Command,
  55     pub sess: &'a Session,
  56 }
  57
  58 impl<'a> GnuLinker<'a> {
  59     fn takes_hints(&self) -> bool {
  60         !self.sess.target.target.options.is_like_osx
  61     }
  62 }
  63
  64 impl<'a> Linker for GnuLinker<'a> {
  65     fn link_dylib(&mut self, lib: &str) { self.cmd.arg("-l").arg(lib); }
  66     fn link_staticlib(&mut self, lib: &str) { self.cmd.arg("-l").arg(lib); }
  67     fn link_rlib(&mut self, lib: &Path) { self.cmd.arg(lib); }
  68     fn include_path(&mut self, path: &Path) { self.cmd.arg("-L").arg(path); }
  69     fn framework_path(&mut self, path: &Path) { self.cmd.arg("-F").arg(path); }
  70     fn output_filename(&mut self, path: &Path) { self.cmd.arg("-o").arg(path); }
  71     fn add_object(&mut self, path: &Path) { self.cmd.arg(path); }
  72     fn position_independent_executable(&mut self) { self.cmd.arg("-pie"); }
  73     fn args(&mut self, args: &[String]) { self.cmd.args(args); }
  74
  75     fn link_rust_dylib(&mut self, lib: &str, _path: &Path) {
  76         self.cmd.arg("-l").arg(lib);
  77     }
  78
  79     fn link_framework(&mut self, framework: &str) {
  80         self.cmd.arg("-framework").arg(framework);
  81     }
  82
  83     fn link_whole_staticlib(&mut self, lib: &str, search_path: &[PathBuf]) {
  84         let target = &self.sess.target.target;
  85         if !target.options.is_like_osx {
  86             self.cmd.arg("-Wl,--whole-archive")
  87                     .arg("-l").arg(lib)
  88                     .arg("-Wl,--no-whole-archive");
  89         } else {
  90             // -force_load is the OSX equivalent of --whole-archive, but it
  91             // involves passing the full path to the library to link.
  92             let mut v = OsString::from("-Wl,-force_load,");
  93             v.push(&archive::find_library(lib, search_path, &self.sess));
  94             self.cmd.arg(&v);
  95         }
  96     }
  97
  98     fn link_whole_rlib(&mut self, lib: &Path) {
  99         if self.sess.target.target.options.is_like_osx {
 100             let mut v = OsString::from("-Wl,-force_load,");
 101             v.push(lib);
 102             self.cmd.arg(&v);
 103         } else {
 104             self.cmd.arg("-Wl,--whole-archive").arg(lib)
 105                     .arg("-Wl,--no-whole-archive");
 106         }
 107     }
 108
 109     fn gc_sections(&mut self, is_dylib: bool) {
 110         // The dead_strip option to the linker specifies that functions and data
 111         // unreachable by the entry point will be removed. This is quite useful
 112         // with Rust's compilation model of compiling libraries at a time into
 113         // one object file. For example, this brings hello world from 1.7MB to
 114         // 458K.
 115         //
 116         // Note that this is done for both executables and dynamic libraries. We
 117         // won't get much benefit from dylibs because LLVM will have already
 118         // stripped away as much as it could. This has not been seen to impact
 119         // link times negatively.
 120         //
 121         // -dead_strip can't be part of the pre_link_args because it's also used
 122         // for partial linking when using multiple codegen units (-r).  So we
 123         // insert it here.
 124         if self.sess.target.target.options.is_like_osx {
 125             self.cmd.arg("-Wl,-dead_strip");
 126
 127         // If we're building a dylib, we don't use --gc-sections because LLVM
 128         // has already done the best it can do, and we also don't want to
 129         // eliminate the metadata. If we're building an executable, however,
 130         // --gc-sections drops the size of hello world from 1.8MB to 597K, a 67%
 131         // reduction.
 132         } else if !is_dylib {
 133             self.cmd.arg("-Wl,--gc-sections");
 134         }
 135     }
 136
 137     fn optimize(&mut self) {
 138         if !self.sess.target.target.options.linker_is_gnu { return }
 139
 140         // GNU-style linkers support optimization with -O. GNU ld doesn't
 141         // need a numeric argument, but other linkers do.
 142         if self.sess.opts.optimize == config::Default ||
 143            self.sess.opts.optimize == config::Aggressive {
 144             self.cmd.arg("-Wl,-O1");
 145         }
 146     }
 147
 148     fn debuginfo(&mut self) {
 149         // Don't do anything special here for GNU-style linkers.
 150     }
 151
 152     fn no_default_libraries(&mut self) {
 153         // Unfortunately right now passing -nodefaultlibs to gcc on windows
 154         // doesn't work so hot (in terms of native dependencies). This if
 155         // statement should hopefully be removed one day though!
 156         if !self.sess.target.target.options.is_like_windows {
 157             self.cmd.arg("-nodefaultlibs");
 158         }
 159     }
 160
 161     fn build_dylib(&mut self, out_filename: &Path) {
 162         // On mac we need to tell the linker to let this library be rpathed
 163         if self.sess.target.target.options.is_like_osx {
 164             self.cmd.args(&["-dynamiclib", "-Wl,-dylib"]);
 165
 166             if self.sess.opts.cg.rpath {
 167                 let mut v = OsString::from("-Wl,-install_name,@rpath/");
 168                 v.push(out_filename.file_name().unwrap());
 169                 self.cmd.arg(&v);
 170             }
 171         } else {
 172             self.cmd.arg("-shared");
 173         }
 174     }
 175
 176     fn whole_archives(&mut self) {
 177         if !self.takes_hints() { return }
 178         self.cmd.arg("-Wl,--whole-archive");
 179     }
 180
 181     fn no_whole_archives(&mut self) {
 182         if !self.takes_hints() { return }
 183         self.cmd.arg("-Wl,--no-whole-archive");
 184     }
 185
 186     fn hint_static(&mut self) {
 187         if !self.takes_hints() { return }
 188         self.cmd.arg("-Wl,-Bstatic");
 189     }
 190
 191     fn hint_dynamic(&mut self) {
 192         if !self.takes_hints() { return }
 193         self.cmd.arg("-Wl,-Bdynamic");
 194     }
 195 }
 196
 197 pub struct MsvcLinker<'a> {
 198     pub cmd: &'a mut Command,
 199     pub sess: &'a Session,
 200 }
 201
 202 impl<'a> Linker for MsvcLinker<'a> {
 203     fn link_rlib(&mut self, lib: &Path) { self.cmd.arg(lib); }
 204     fn add_object(&mut self, path: &Path) { self.cmd.arg(path); }
 205     fn args(&mut self, args: &[String]) { self.cmd.args(args); }
 206     fn build_dylib(&mut self, _out_filename: &Path) { self.cmd.arg("/DLL"); }
 207     fn gc_sections(&mut self, _is_dylib: bool) { self.cmd.arg("/OPT:REF,ICF"); }
 208
 209     fn link_dylib(&mut self, lib: &str) {
 210         self.cmd.arg(&format!("{}.lib", lib));
 211     }
 212
 213     fn link_rust_dylib(&mut self, lib: &str, path: &Path) {
 214         // When producing a dll, the MSVC linker may not actually emit a
 215         // `foo.lib` file if the dll doesn't actually export any symbols, so we
 216         // check to see if the file is there and just omit linking to it if it's
 217         // not present.
 218         let name = format!("{}.lib", lib);
 219         if fs::metadata(&path.join(&name)).is_ok() {
 220             self.cmd.arg(name);
 221         }
 222     }
 223
 224     fn link_staticlib(&mut self, lib: &str) {
 225         self.cmd.arg(&format!("{}.lib", lib));
 226     }
 227
 228     fn position_independent_executable(&mut self) {
 229         // noop
 230     }
 231
 232     fn no_default_libraries(&mut self) {
 233         // Currently we don't pass the /NODEFAULTLIB flag to the linker on MSVC
 234         // as there's been trouble in the past of linking the C++ standard
 235         // library required by LLVM. This likely needs to happen one day, but
 236         // in general Windows is also a more controlled environment than
 237         // Unix, so it's not necessarily as critical that this be implemented.
 238         //
 239         // Note that there are also some licensing worries about statically
 240         // linking some libraries which require a specific agreement, so it may
 241         // not ever be possible for us to pass this flag.
 242     }
 243
 244     fn include_path(&mut self, path: &Path) {
 245         let mut arg = OsString::from("/LIBPATH:");
 246         arg.push(path);
 247         self.cmd.arg(&arg);
 248     }
 249
 250     fn output_filename(&mut self, path: &Path) {
 251         let mut arg = OsString::from("/OUT:");
 252         arg.push(path);
 253         self.cmd.arg(&arg);
 254     }
 255
 256     fn framework_path(&mut self, _path: &Path) {
 257         panic!("frameworks are not supported on windows")
 258     }
 259     fn link_framework(&mut self, _framework: &str) {
 260         panic!("frameworks are not supported on windows")
 261     }
 262
 263     fn link_whole_staticlib(&mut self, lib: &str, _search_path: &[PathBuf]) {
 264         // not supported?
 265         self.link_staticlib(lib);
 266     }
 267     fn link_whole_rlib(&mut self, path: &Path) {
 268         // not supported?
 269         self.link_rlib(path);
 270     }
 271     fn optimize(&mut self) {
 272         // Needs more investigation of `/OPT` arguments
 273     }
 274
 275     fn debuginfo(&mut self) {
 276         match self.sess.opts.debuginfo {
 277             NoDebugInfo => {
 278                 // Do nothing if debuginfo is disabled
 279             },
 280             LimitedDebugInfo |
 281             FullDebugInfo    => {
 282                 // This will cause the Microsoft linker to generate a PDB file
 283                 // from the CodeView line tables in the object files.
 284                 self.cmd.arg("/DEBUG");
 285             }
 286         }
 287     }
 288
 289     fn whole_archives(&mut self) {
 290         // hints not supported?
 291     }
 292     fn no_whole_archives(&mut self) {
 293         // hints not supported?
 294     }
 295
 296     // On windows static libraries are of the form `foo.lib` and dynamic
 297     // libraries are not linked against directly, but rather through their
 298     // import libraries also called `foo.lib`. As a result there's no
 299     // possibility for a native library to appear both dynamically and
 300     // statically in the same folder so we don't have to worry about hints like
 301     // we do on Unix platforms.
 302     fn hint_static(&mut self) {}
 303     fn hint_dynamic(&mut self) {}
 304 }