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_span::symbol::Symbol;
11 use rustc_target::spec::LldFlavor;
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 {
42 Command { program, args: Vec::new(), env: Vec::new(), env_remove: Vec::new() }
45 pub fn arg<P: AsRef<OsStr>>(&mut self, arg: P) -> &mut Command {
46 self._arg(arg.as_ref());
50 pub fn sym_arg(&mut self, arg: Symbol) -> &mut Command {
51 self.arg(&*arg.as_str());
55 pub fn args<I>(&mut self, args: I) -> &mut Command
57 I: IntoIterator<Item: AsRef<OsStr>>,
60 self._arg(arg.as_ref());
65 fn _arg(&mut self, arg: &OsStr) {
66 self.args.push(arg.to_owned());
69 pub fn env<K, V>(&mut self, key: K, value: V) -> &mut Command
74 self._env(key.as_ref(), value.as_ref());
78 fn _env(&mut self, key: &OsStr, value: &OsStr) {
79 self.env.push((key.to_owned(), value.to_owned()));
82 pub fn env_remove<K>(&mut self, key: K) -> &mut Command
86 self._env_remove(key.as_ref());
90 fn _env_remove(&mut self, key: &OsStr) {
91 self.env_remove.push(key.to_owned());
94 pub fn output(&mut self) -> io::Result<Output> {
95 self.command().output()
98 pub fn command(&self) -> process::Command {
99 let mut ret = match self.program {
100 Program::Normal(ref p) => process::Command::new(p),
101 Program::CmdBatScript(ref p) => {
102 let mut c = process::Command::new("cmd");
106 Program::Lld(ref p, flavor) => {
107 let mut c = process::Command::new(p);
108 c.arg("-flavor").arg(match flavor {
109 LldFlavor::Wasm => "wasm",
110 LldFlavor::Ld => "gnu",
111 LldFlavor::Link => "link",
112 LldFlavor::Ld64 => "darwin",
117 ret.args(&self.args);
118 ret.envs(self.env.clone());
119 for k in &self.env_remove {
127 pub fn get_args(&self) -> &[OsString] {
131 pub fn take_args(&mut self) -> Vec<OsString> {
132 mem::take(&mut self.args)
135 /// Returns a `true` if we're pretty sure that this'll blow OS spawn limits,
136 /// or `false` if we should attempt to spawn and see what the OS says.
137 pub fn very_likely_to_exceed_some_spawn_limit(&self) -> bool {
138 // We mostly only care about Windows in this method, on Unix the limits
139 // can be gargantuan anyway so we're pretty unlikely to hit them
144 // Right now LLD doesn't support the `@` syntax of passing an argument
145 // through files, so regardless of the platform we try to go to the OS
147 if let Program::Lld(..) = self.program {
151 // Ok so on Windows to spawn a process is 32,768 characters in its
152 // command line [1]. Unfortunately we don't actually have access to that
153 // as it's calculated just before spawning. Instead we perform a
154 // poor-man's guess as to how long our command line will be. We're
155 // assuming here that we don't have to escape every character...
157 // Turns out though that `cmd.exe` has even smaller limits, 8192
158 // characters [2]. Linkers can often be batch scripts (for example
159 // Emscripten, Gecko's current build system) which means that we're
160 // running through batch scripts. These linkers often just forward
161 // arguments elsewhere (and maybe tack on more), so if we blow 8192
162 // bytes we'll typically cause them to blow as well.
164 // Basically as a result just perform an inflated estimate of what our
165 // command line will look like and test if it's > 8192 (we actually
166 // test against 6k to artificially inflate our estimate). If all else
167 // fails we'll fall back to the normal unix logic of testing the OS
168 // error code if we fail to spawn and automatically re-spawning the
169 // linker with smaller arguments.
171 // [1]: https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-createprocessa
172 // [2]: https://devblogs.microsoft.com/oldnewthing/?p=41553
174 let estimated_command_line_len = self.args.iter().map(|a| a.len()).sum::<usize>();
175 estimated_command_line_len > 1024 * 6
179 impl fmt::Debug for Command {
180 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
181 self.command().fmt(f)