test propagating env vars from build.rs to binary

Author: RalfJung

cargo-miri/bin.rs

@@ -612,7 +612,9 @@ fn phase_cargo_runner(binary: &Path, binary_args: env::Args) {
     let info: CrateRunInfo = serde_json::from_reader(file)
         .unwrap_or_else(|_| show_error(format!("File {:?} does not contain valid JSON", binary)));
 
-    // Set missing env vars.
+    // Set missing env vars. Looks like `build.rs` vars are still set at run-time, but
+    // `CARGO_BIN_EXE_*` are not. This means we can give the run-time environment precedence,
+    // to rather do too little than too much.
     for (name, val) in info.env {
         if env::var_os(&name).is_none() {
             env::set_var(name, val);

test-cargo-miri/build.rs

@@ -12,4 +12,6 @@ fn not_in_miri() -> i32 {
 fn main() {
     not_in_miri();
     println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo:rerun-if-env-changed=MIRITESTVAR");
+    println!("cargo:rustc-env=MIRITESTVAR=testval");
 }

test-cargo-miri/run-test.py

@@ -50,11 +50,14 @@ def test(name, cmd, stdout_ref, stderr_ref, stdin=b'', env={}):
         fail("stderr does not match reference")
 
 def test_cargo_miri_run():
-    test("`cargo miri run`",
+    test("`cargo miri run` (without isolation)",
         cargo_miri("run"),
         "stdout.ref1", "stderr.ref1",
         stdin=b'12\n21\n',
-        env={'MIRIFLAGS': "-Zmiri-disable-isolation"},
+        env={
+            'MIRIFLAGS': "-Zmiri-disable-isolation",
+            'MIRITESTVAR': "wrongval", # make sure the build.rs value takes precedence
+        },
     )
     test("`cargo miri run` (with arguments and target)",
         cargo_miri("run") + ["--bin", "cargo-miri-test", "--", "hello world", '"hello world"'],

test-cargo-miri/src/main.rs

@@ -3,6 +3,9 @@ use byteorder::{BigEndian, ByteOrder};
 use std::io::{self, BufRead};
 
 fn main() {
+    // Check env var set by `build.rs`.
+    assert_eq!(env!("MIRITESTVAR"), "testval");
+
     // Exercise external crate, printing to stdout.
     let buf = &[1,2,3,4];
     let n = <BigEndian as ByteOrder>::read_u32(buf);