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Rollup merge of #74803 - infinity0:fix-exec, r=nagisa
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rustbuild: fix bad usage of UNIX exec() in rustc wrapper

exec never returns, it replaces the current process. so anything after it is unreachable. that's not how exec_cmd() is used in the surrounding code

We use `--on-fail env` on Debian. `env` always returns exit code 0. This means that the `rustc` bootstrap wrapper always returns exit code 0 even when it fails. However, the crossbeam-utils build process (due to autocfg) relies on `rustc` returning error exit codes when detecting CPU features, and ends up writing `cargo:rustc-cfg=has_atomic_u128` even when it's not detected, because the `rustc` wrapper is always giving exit code 0.

(This separately is causing our builds to try to compile rustc 40+ times, due to #74801.)
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Manishearth authored Jul 27, 2020
2 parents e054340 + b99668b commit c9cdc87
Showing 1 changed file with 3 additions and 10 deletions.
13 changes: 3 additions & 10 deletions src/bootstrap/bin/rustc.rs
Original file line number Diff line number Diff line change
Expand Up @@ -153,7 +153,7 @@ fn main() {
e => e,
};
println!("\nDid not run successfully: {:?}\n{:?}\n-------------", e, cmd);
exec_cmd(&mut on_fail).expect("could not run the backup command");
status_code(&mut on_fail).expect("could not run the backup command");
std::process::exit(1);
}

Expand Down Expand Up @@ -182,17 +182,10 @@ fn main() {
}
}

let code = exec_cmd(&mut cmd).unwrap_or_else(|_| panic!("\n\n failed to run {:?}", cmd));
let code = status_code(&mut cmd).unwrap_or_else(|_| panic!("\n\n failed to run {:?}", cmd));
std::process::exit(code);
}

#[cfg(unix)]
fn exec_cmd(cmd: &mut Command) -> io::Result<i32> {
use std::os::unix::process::CommandExt;
Err(cmd.exec())
}

#[cfg(not(unix))]
fn exec_cmd(cmd: &mut Command) -> io::Result<i32> {
fn status_code(cmd: &mut Command) -> io::Result<i32> {
cmd.status().map(|status| status.code().unwrap())
}

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