testcase(Problem)

tests/testsuite/build_script.rs

@@ -5527,3 +5527,90 @@ fn test_old_syntax_with_old_msrv() {
     p.cargo("build -v").run();
     p.cargo("run -v").with_stdout("foo\n").run();
 }
+
+#[cargo_test]
+fn build_script_rerun_when_target_rustflags_change() {
+    let target = rustc_host();
+    let p = project()
+        .file(
+            "src/lib.rs",
+            "#![allow(warnings)]
+#![cfg_attr(backtrace, feature(mixed_integer_ops))]
+            ",
+        )
+        .file(
+            "build.rs",
+            r#"
+            use std::env;
+            use std::process::{Command, Stdio};
+            fn main() {
+                let rustc = env::var_os("RUSTC").unwrap();
+                let mut cmd = Command::new(rustc);
+                cmd.stderr(Stdio::null())
+                    .arg("--crate-type=lib")
+                    .arg("--out-dir")
+                    .arg(env::var_os("OUT_DIR").unwrap())
+                    .arg("build/probe.rs");
+                cmd.arg("--target").arg(env::var_os("TARGET").unwrap());
+                if let Ok(rustflags) = env::var("CARGO_ENCODED_RUSTFLAGS") {
+                    if !rustflags.is_empty() {
+                        for arg in rustflags.split('\x1f') {
+                            cmd.arg(arg);
+                        }
+                    }
+                }
+                let _ = cmd
+                    .status()
+                    .ok()
+                    .unwrap()
+                    .success()
+                    .then(|| println!("cargo:rustc-cfg=backtrace"));
+            }
+            "#,
+        )
+        .file(
+            "Cargo.toml",
+            r#"
+        [package]
+        name = "foo"
+        version = "0.0.1"
+        authors = [""]
+        edition = "2021"
+        
+        [features]
+        default = ["std"]
+        std = []
+        "#,
+        )
+        .file("build/probe.rs", "#![feature(mixed_integer_ops)]")
+        .build();
+
+    p.cargo("build --target")
+        .arg(&target)
+        .with_stderr(
+            "\
+[COMPILING] foo v0.0.1 ([..])
+[FINISHED] [..]
+",
+        )
+        .run();
+
+    p.cargo("build --target")
+        .arg(&target)
+        .env("RUSTFLAGS", "-Zallow-features=")
+        .with_status(101)
+        .with_stderr(
+            "\
+[COMPILING] foo v0.0.1 ([..])
+error[E0725]: the feature `mixed_integer_ops` is not in the list of allowed features
+ --> src/lib.rs:2:32
+  |
+2 | #![cfg_attr(backtrace, feature(mixed_integer_ops))]
+  |                                ^^^^^^^^^^^^^^^^^
+
+For more information about this error, try `rustc --explain E0725`.
+[ERROR] could not compile `foo` (lib) due to 1 previous error
+",
+        )
+        .run();
+}