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Include Cargo rustc configuration in probe
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Without this, environments that configure `RUSTFLAGS` or the
`RUSTC_WRAPPER` in ways that break compilation with `backtrace` will
fail to compile anyhow (see dtolnay#156).

With this, the compiler probe takes into account that Cargo
configuration, and thus (more) accurately represents whether the
`backtrace` feature can be safely enabled.

Requires rust-lang/cargo#9601, but does not break without.

Fixes dtolnay#156.
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Jon Gjengset committed Aug 13, 2021
1 parent 2778943 commit 6c20a06
Showing 1 changed file with 25 additions and 5 deletions.
30 changes: 25 additions & 5 deletions build.rs
Original file line number Diff line number Diff line change
Expand Up @@ -67,17 +67,37 @@ fn compile_probe() -> Option<ExitStatus> {
let out_dir = env::var_os("OUT_DIR")?;
let probefile = Path::new(&out_dir).join("probe.rs");
fs::write(&probefile, PROBE).ok()?;
Command::new(rustc)
.stderr(Stdio::null())

// Make sure to pick up Cargo rustc configuration.
let mut cmd = env::var_os("CARGO_RUSTC_WRAPPER").map_or_else(
|| Command::new(&rustc),
|wrapper| {
let mut cmd = Command::new(wrapper);
// The wrapper's first argument should always be the path to rustc.
cmd.arg(&rustc);
cmd
},
);

cmd.stderr(Stdio::null())
.arg("--edition=2018")
.arg("--crate-name=anyhow_build")
.arg("--crate-type=lib")
.arg("--emit=metadata")
.arg("--out-dir")
.arg(out_dir)
.arg(probefile)
.status()
.ok()
.arg(probefile);

// If Cargo wants to set RUSTFLAGS, use that.
if let Ok(rustflags) = env::var("CARGO_ENCODED_RUSTFLAGS") {
if !rustflags.is_empty() {
for arg in rustflags.split('\x1f') {
cmd.arg(arg);
}
}
}

cmd.status().ok()
}

fn rustc_minor_version() -> Option<u32> {
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