1 //! A thin wrapper around `Command` in the standard library which allows us to
2 //! read the arguments that are built up.
4 use std::ffi::{OsStr, OsString};
8 use std::process::{self, Output};
10 use rustc_target::spec::LldFlavor;
11 use syntax::symbol::Symbol;
17 env: Vec<(OsString, OsString)>,
18 env_remove: Vec<OsString>,
24 CmdBatScript(OsString),
25 Lld(OsString, LldFlavor)
29 pub fn new<P: AsRef<OsStr>>(program: P) -> Command {
30 Command::_new(Program::Normal(program.as_ref().to_owned()))
33 pub fn bat_script<P: AsRef<OsStr>>(program: P) -> Command {
34 Command::_new(Program::CmdBatScript(program.as_ref().to_owned()))
37 pub fn lld<P: AsRef<OsStr>>(program: P, flavor: LldFlavor) -> Command {
38 Command::_new(Program::Lld(program.as_ref().to_owned(), flavor))
41 fn _new(program: Program) -> Command {
46 env_remove: Vec::new(),
50 pub fn arg<P: AsRef<OsStr>>(&mut self, arg: P) -> &mut Command {
51 self._arg(arg.as_ref());
55 pub fn sym_arg(&mut self, arg: Symbol) -> &mut Command {
56 self.arg(&*arg.as_str());
60 pub fn args<I>(&mut self, args: I) -> &mut Command
62 I: IntoIterator<Item: AsRef<OsStr>>,
65 self._arg(arg.as_ref());
70 fn _arg(&mut self, arg: &OsStr) {
71 self.args.push(arg.to_owned());
74 pub fn env<K, V>(&mut self, key: K, value: V) -> &mut Command
75 where K: AsRef<OsStr>,
78 self._env(key.as_ref(), value.as_ref());
82 fn _env(&mut self, key: &OsStr, value: &OsStr) {
83 self.env.push((key.to_owned(), value.to_owned()));
86 pub fn env_remove<K>(&mut self, key: K) -> &mut Command
87 where K: AsRef<OsStr>,
89 self._env_remove(key.as_ref());
93 fn _env_remove(&mut self, key: &OsStr) {
94 self.env_remove.push(key.to_owned());
97 pub fn output(&mut self) -> io::Result<Output> {
98 self.command().output()
101 pub fn command(&self) -> process::Command {
102 let mut ret = match self.program {
103 Program::Normal(ref p) => process::Command::new(p),
104 Program::CmdBatScript(ref p) => {
105 let mut c = process::Command::new("cmd");
109 Program::Lld(ref p, flavor) => {
110 let mut c = process::Command::new(p);
111 c.arg("-flavor").arg(match flavor {
112 LldFlavor::Wasm => "wasm",
113 LldFlavor::Ld => "gnu",
114 LldFlavor::Link => "link",
115 LldFlavor::Ld64 => "darwin",
120 ret.args(&self.args);
121 ret.envs(self.env.clone());
122 for k in &self.env_remove {
130 pub fn get_args(&self) -> &[OsString] {
134 pub fn take_args(&mut self) -> Vec<OsString> {
135 mem::take(&mut self.args)
138 /// Returns a `true` if we're pretty sure that this'll blow OS spawn limits,
139 /// or `false` if we should attempt to spawn and see what the OS says.
140 pub fn very_likely_to_exceed_some_spawn_limit(&self) -> bool {
141 // We mostly only care about Windows in this method, on Unix the limits
142 // can be gargantuan anyway so we're pretty unlikely to hit them
147 // Right now LLD doesn't support the `@` syntax of passing an argument
148 // through files, so regardless of the platform we try to go to the OS
150 if let Program::Lld(..) = self.program {
154 // Ok so on Windows to spawn a process is 32,768 characters in its
155 // command line [1]. Unfortunately we don't actually have access to that
156 // as it's calculated just before spawning. Instead we perform a
157 // poor-man's guess as to how long our command line will be. We're
158 // assuming here that we don't have to escape every character...
160 // Turns out though that `cmd.exe` has even smaller limits, 8192
161 // characters [2]. Linkers can often be batch scripts (for example
162 // Emscripten, Gecko's current build system) which means that we're
163 // running through batch scripts. These linkers often just forward
164 // arguments elsewhere (and maybe tack on more), so if we blow 8192
165 // bytes we'll typically cause them to blow as well.
167 // Basically as a result just perform an inflated estimate of what our
168 // command line will look like and test if it's > 8192 (we actually
169 // test against 6k to artificially inflate our estimate). If all else
170 // fails we'll fall back to the normal unix logic of testing the OS
171 // error code if we fail to spawn and automatically re-spawning the
172 // linker with smaller arguments.
174 // [1]: https://msdn.microsoft.com/en-us/library/windows/desktop/ms682425(v=vs.85).aspx
175 // [2]: https://blogs.msdn.microsoft.com/oldnewthing/20031210-00/?p=41553
177 let estimated_command_line_len =
178 self.args.iter().map(|a| a.len()).sum::<usize>();
179 estimated_command_line_len > 1024 * 6
183 impl fmt::Debug for Command {
184 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
185 self.command().fmt(f)