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Auto merge of rust-lang#116448 - Kobzol:bootstrap-host-flags, r=onur-…
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…ozkan,petrochenkov

Pass rustc shim flags using environment variable

This PR implements a generalized way of passing of host flags to the `rustc` shim in bootstrap, as proposed [here](rust-lang#116278 (comment)).

I tried to implement the bootstrap side using `OsString`, but then I realized that the shim code was using `env::var` before anyway, instead of `env::var_os`, so I just settled on a `String`. The shim side is still general and uses `env::vars_os` now.

I'm not sure if we actually need to do something with the `rustdoc` shim. It *seems* to me that the env. vars passed to it (`RUSTDOC_LINKER`) and (`RUSTDOC_LLD_NO_THREADS`) could just be passed to cargo directly (or rather, the commands that they invoke in the shim could be passed directly). I'm not sure why are they set by the shim.

r? `@onur-ozkan`
CC `@petrochenkov`
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@bors
bors committed Oct 11, 2023
2 parents 475c71d + 3f9ab7a commit 9d1e4b7
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Showing 3 changed files with 57 additions and 37 deletions.
1 change: 1 addition & 0 deletions src/bootstrap/bin/_helper.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@ fn parse_rustc_verbose() -> usize {
/// Parses the value of the "RUSTC_STAGE" environment variable and returns it as a `String`.
///
/// If "RUSTC_STAGE" was not set, the program will be terminated with 101.
#[allow(unused)]
fn parse_rustc_stage() -> String {
std::env::var("RUSTC_STAGE").unwrap_or_else(|_| {
// Don't panic here; it's reasonable to try and run these shims directly. Give a helpful error instead.
Expand Down
34 changes: 5 additions & 29 deletions src/bootstrap/bin/rustc.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,6 @@ fn main() {
let args = env::args_os().skip(1).collect::<Vec<_>>();
let arg = |name| args.windows(2).find(|args| args[0] == name).and_then(|args| args[1].to_str());

let stage = parse_rustc_stage();
let verbose = parse_rustc_verbose();

// Detect whether or not we're a build script depending on whether --target
Expand Down Expand Up @@ -108,36 +107,13 @@ fn main() {
cmd.arg("-Ztls-model=initial-exec");
}
} else {
// FIXME(rust-lang/cargo#5754) we shouldn't be using special env vars
// here, but rather Cargo should know what flags to pass rustc itself.

// Override linker if necessary.
if let Ok(host_linker) = env::var("RUSTC_HOST_LINKER") {
cmd.arg(format!("-Clinker={host_linker}"));
}
if env::var_os("RUSTC_HOST_FUSE_LD_LLD").is_some() {
cmd.arg("-Clink-args=-fuse-ld=lld");
}

if let Ok(s) = env::var("RUSTC_HOST_CRT_STATIC") {
if s == "true" {
cmd.arg("-C").arg("target-feature=+crt-static");
// Find any host flags that were passed by bootstrap.
// The flags are stored in a RUSTC_HOST_FLAGS variable, separated by spaces.
if let Ok(flags) = std::env::var("RUSTC_HOST_FLAGS") {
for flag in flags.split(' ') {
cmd.arg(flag);
}
if s == "false" {
cmd.arg("-C").arg("target-feature=-crt-static");
}
}

// Cargo doesn't pass RUSTFLAGS to proc_macros:
// https://github.com/rust-lang/cargo/issues/4423
// Thus, if we are on stage 0, we explicitly set `--cfg=bootstrap`.
// We also declare that the flag is expected, which we need to do to not
// get warnings about it being unexpected.
if stage == "0" {
cmd.arg("--cfg=bootstrap");
}
cmd.arg("-Zunstable-options");
cmd.arg("--check-cfg=values(bootstrap)");
}

if let Ok(map) = env::var("RUSTC_DEBUGINFO_MAP") {
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59 changes: 51 additions & 8 deletions src/bootstrap/builder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1174,9 +1174,6 @@ impl<'a> Builder<'a> {
if let Some(linker) = self.linker(compiler.host) {
cmd.env("RUSTDOC_LINKER", linker);
}
if self.is_fuse_ld_lld(compiler.host) {
cmd.env("RUSTDOC_FUSE_LD_LLD", "1");
}
cmd
}

Expand Down Expand Up @@ -1268,6 +1265,8 @@ impl<'a> Builder<'a> {
let mut cargo = self.bare_cargo(compiler, mode, target, cmd);
let out_dir = self.stage_out(compiler, mode);

let mut hostflags = HostFlags::default();

// Codegen backends are not yet tracked by -Zbinary-dep-depinfo,
// so we need to explicitly clear out if they've been updated.
for backend in self.codegen_backends(compiler) {
Expand Down Expand Up @@ -1439,6 +1438,20 @@ impl<'a> Builder<'a> {
}
}

// FIXME(rust-lang/cargo#5754) we shouldn't be using special command arguments
// to the host invocation here, but rather Cargo should know what flags to pass rustc
// itself.
if stage == 0 {
hostflags.arg("--cfg=bootstrap");
}
// Cargo doesn't pass RUSTFLAGS to proc_macros:
// https://github.com/rust-lang/cargo/issues/4423
// Thus, if we are on stage 0, we explicitly set `--cfg=bootstrap`.
// We also declare that the flag is expected, which we need to do to not
// get warnings about it being unexpected.
hostflags.arg("-Zunstable-options");
hostflags.arg("--check-cfg=values(bootstrap)");

// FIXME: It might be better to use the same value for both `RUSTFLAGS` and `RUSTDOCFLAGS`,
// but this breaks CI. At the very least, stage0 `rustdoc` needs `--cfg bootstrap`. See
// #71458.
Expand Down Expand Up @@ -1655,11 +1668,10 @@ impl<'a> Builder<'a> {
}

if let Some(host_linker) = self.linker(compiler.host) {
cargo.env("RUSTC_HOST_LINKER", host_linker);
hostflags.arg(format!("-Clinker={}", host_linker.display()));
}
if self.is_fuse_ld_lld(compiler.host) {
cargo.env("RUSTC_HOST_FUSE_LD_LLD", "1");
cargo.env("RUSTDOC_FUSE_LD_LLD", "1");
hostflags.arg("-Clink-args=-fuse-ld=lld");
}

if let Some(target_linker) = self.linker(target) {
Expand Down Expand Up @@ -1743,7 +1755,8 @@ impl<'a> Builder<'a> {
}

if let Some(x) = self.crt_static(compiler.host) {
cargo.env("RUSTC_HOST_CRT_STATIC", x.to_string());
let sign = if x { "+" } else { "-" };
hostflags.arg(format!("-Ctarget-feature={sign}crt-static"));
}

if let Some(map_to) = self.build.debuginfo_map_to(GitRepo::Rustc) {
Expand Down Expand Up @@ -2055,7 +2068,7 @@ impl<'a> Builder<'a> {
cargo.env("RUSTFLAGS", &rustc_args.join(" "));
}

Cargo { command: cargo, rustflags, rustdocflags, allow_features }
Cargo { command: cargo, rustflags, rustdocflags, hostflags, allow_features }
}

/// Ensure that a given step is built, returning its output. This will
Expand Down Expand Up @@ -2233,11 +2246,36 @@ impl Rustflags {
}
}

/// Flags that are passed to the `rustc` shim binary.
/// These flags will only be applied when compiling host code, i.e. when
/// `--target` is unset.
#[derive(Debug, Default)]
pub struct HostFlags {
rustc: Vec<String>,
}

impl HostFlags {
const SEPARATOR: &'static str = " ";

/// Adds a host rustc flag.
fn arg<S: Into<String>>(&mut self, flag: S) {
let value = flag.into().trim().to_string();
assert!(!value.contains(Self::SEPARATOR));
self.rustc.push(value);
}

/// Encodes all the flags into a single string.
fn encode(self) -> String {
self.rustc.join(Self::SEPARATOR)
}
}

#[derive(Debug)]
pub struct Cargo {
command: Command,
rustflags: Rustflags,
rustdocflags: Rustflags,
hostflags: HostFlags,
allow_features: String,
}

Expand Down Expand Up @@ -2309,6 +2347,11 @@ impl From<Cargo> for Command {
cargo.command.env("RUSTDOCFLAGS", rustdocflags);
}

let encoded_hostflags = cargo.hostflags.encode();
if !encoded_hostflags.is_empty() {
cargo.command.env("RUSTC_HOST_FLAGS", encoded_hostflags);
}

if !cargo.allow_features.is_empty() {
cargo.command.env("RUSTC_ALLOW_FEATURES", cargo.allow_features);
}
Expand Down

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