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;
16 env: Vec<(OsString, OsString)>,
17 env_remove: Vec<OsString>,
23 CmdBatScript(OsString),
24 Lld(OsString, LldFlavor),
28 pub fn new<P: AsRef<OsStr>>(program: P) -> Command {
29 Command::_new(Program::Normal(program.as_ref().to_owned()))
32 pub fn bat_script<P: AsRef<OsStr>>(program: P) -> Command {
33 Command::_new(Program::CmdBatScript(program.as_ref().to_owned()))
36 pub fn lld<P: AsRef<OsStr>>(program: P, flavor: LldFlavor) -> Command {
37 Command::_new(Program::Lld(program.as_ref().to_owned(), flavor))
40 fn _new(program: Program) -> Command {
41 Command { program, args: Vec::new(), env: Vec::new(), env_remove: Vec::new() }
44 pub fn arg<P: AsRef<OsStr>>(&mut self, arg: P) -> &mut Command {
45 self._arg(arg.as_ref());
49 pub fn args<I>(&mut self, args: I) -> &mut Command
51 I: IntoIterator<Item: AsRef<OsStr>>,
54 self._arg(arg.as_ref());
59 fn _arg(&mut self, arg: &OsStr) {
60 self.args.push(arg.to_owned());
63 pub fn env<K, V>(&mut self, key: K, value: V) -> &mut Command
68 self._env(key.as_ref(), value.as_ref());
72 fn _env(&mut self, key: &OsStr, value: &OsStr) {
73 self.env.push((key.to_owned(), value.to_owned()));
76 pub fn env_remove<K>(&mut self, key: K) -> &mut Command
80 self._env_remove(key.as_ref());
84 fn _env_remove(&mut self, key: &OsStr) {
85 self.env_remove.push(key.to_owned());
88 pub fn output(&mut self) -> io::Result<Output> {
89 self.command().output()
92 pub fn command(&self) -> process::Command {
93 let mut ret = match self.program {
94 Program::Normal(ref p) => process::Command::new(p),
95 Program::CmdBatScript(ref p) => {
96 let mut c = process::Command::new("cmd");
100 Program::Lld(ref p, flavor) => {
101 let mut c = process::Command::new(p);
102 c.arg("-flavor").arg(flavor.as_str());
103 if let LldFlavor::Wasm = flavor {
104 // LLVM expects host-specific formatting for @file
105 // arguments, but we always generate posix formatted files
106 // at this time. Indicate as such.
107 c.arg("--rsp-quoting=posix");
112 ret.args(&self.args);
113 ret.envs(self.env.clone());
114 for k in &self.env_remove {
122 pub fn get_args(&self) -> &[OsString] {
126 pub fn take_args(&mut self) -> Vec<OsString> {
127 mem::take(&mut self.args)
130 /// Returns a `true` if we're pretty sure that this'll blow OS spawn limits,
131 /// or `false` if we should attempt to spawn and see what the OS says.
132 pub fn very_likely_to_exceed_some_spawn_limit(&self) -> bool {
133 // We mostly only care about Windows in this method, on Unix the limits
134 // can be gargantuan anyway so we're pretty unlikely to hit them
139 // Right now LLD doesn't support the `@` syntax of passing an argument
140 // through files, so regardless of the platform we try to go to the OS
142 if let Program::Lld(..) = self.program {
146 // Ok so on Windows to spawn a process is 32,768 characters in its
147 // command line [1]. Unfortunately we don't actually have access to that
148 // as it's calculated just before spawning. Instead we perform a
149 // poor-man's guess as to how long our command line will be. We're
150 // assuming here that we don't have to escape every character...
152 // Turns out though that `cmd.exe` has even smaller limits, 8192
153 // characters [2]. Linkers can often be batch scripts (for example
154 // Emscripten, Gecko's current build system) which means that we're
155 // running through batch scripts. These linkers often just forward
156 // arguments elsewhere (and maybe tack on more), so if we blow 8192
157 // bytes we'll typically cause them to blow as well.
159 // Basically as a result just perform an inflated estimate of what our
160 // command line will look like and test if it's > 8192 (we actually
161 // test against 6k to artificially inflate our estimate). If all else
162 // fails we'll fall back to the normal unix logic of testing the OS
163 // error code if we fail to spawn and automatically re-spawning the
164 // linker with smaller arguments.
166 // [1]: https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-createprocessa
167 // [2]: https://devblogs.microsoft.com/oldnewthing/?p=41553
169 let estimated_command_line_len = self.args.iter().map(|a| a.len()).sum::<usize>();
170 estimated_command_line_len > 1024 * 6
174 impl fmt::Debug for Command {
175 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
176 self.command().fmt(f)