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fix: avoid inserting duplicate dylib_path_envvar when calling cargo run recursively #14464

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Oct 8, 2024
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fix: avoid inserting duplicate dylib_path_envvar when calling cargo run recursively #14464

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e888c13
test: Add test for issue-14194
linyihai Aug 28, 2024
54dbc2b
fix: Avoid inserting `search_path` again.
linyihai Aug 28, 2024
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6 changes: 5 additions & 1 deletion src/cargo/core/compiler/compilation.rs
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The reason this approach didn't work is pretty much due to #10358. When Cargo computes fingerprint for a Unit of work, it asks env::var which doesn't contain LIBRARY_PATH or PATH because that is set by Cargo. rerun-if-env-changed only captures environment variables set by users via shell like MY_VAR=1 cargo build. Variables added by Cargo only available when consulting the Command struct of the build script execution via Command::get_envs (like what has done in f91dc78).

As a consequence, if you open the fingerprint JSON file of the build script execution (normally at target/debug/.fingerprint/foo-559e30894cda9925/run-build-script-build-script-build.json), you'll see

{
  "rustc": 11851488446658826000,
  // ...
  "local": [
    {
      "RerunIfEnvChanged": {
        "var": "DYLD_FALLBACK_LIBRARY_PATH",
        "val": null
      }
    }
  ],
  "rustflags": [],
  // ...
}

which shows that Cargo failed to capture the initial library search path set by itself.

There is another way to observe this bug: set the LEVEL env var in the test to a higher number like 5. Any subsequent Cargo invocation after the first one should be fresh. Before doing this verification you need to change std::env!("LEVEL") to std::env::var!("LEVEL") because the former will be captured by rustc dep-info, which trigger a rebuild.

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Before doing this verification you need to change std::env!("LEVEL") to std::env::var!("LEVEL") because the former will be captured by rustc dep-info, which trigger a rebuild.

I didn't expect such a difference.

I decide to to get the "LEVEL" from the command line argument.

Original file line number Diff line number Diff line change
Expand Up @@ -323,7 +323,11 @@ impl<'gctx> Compilation<'gctx> {

let dylib_path = paths::dylib_path();
let dylib_path_is_empty = dylib_path.is_empty();
search_path.extend(dylib_path.into_iter());
if dylib_path.starts_with(&search_path) {
search_path = dylib_path;
} else {
search_path.extend(dylib_path.into_iter());
}
if cfg!(target_os = "macos") && dylib_path_is_empty {
// These are the defaults when DYLD_FALLBACK_LIBRARY_PATH isn't
// set or set to an empty string. Since Cargo is explicitly setting
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60 changes: 60 additions & 0 deletions tests/testsuite/build.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2154,6 +2154,66 @@ fn crate_library_path_env_var() {
setenv_for_removing_empty_component(p.cargo("run")).run();
}

// See https://github.com/rust-lang/cargo/issues/14194
#[cargo_test]
fn issue_14194_deduplicate_library_path_env_var() {
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let p = project()
.file(
"src/main.rs",
&format!(
r#"
use std::process::Command;
fn main() {{
let level: i32 = std::env::args().nth(1).unwrap().parse().unwrap();
let txt = "var.txt";
let lib_path = std::env::var("{}").unwrap();

// Make sure we really have something in dylib search path.
let count = std::env::split_paths(&lib_path).count();
assert!(count > 0);

if level >= 3 {{
std::fs::write(txt, &lib_path).unwrap();
}} else {{
let prev_lib_path = std::fs::read_to_string(txt).unwrap();
// Ensure no duplicate insertion to dylib search paths
// when calling `cargo run` recursively.
assert_eq!(lib_path, prev_lib_path);
}}

if level == 0 {{
return;
}}

let _ = Command::new(std::env!("CARGO"))
.arg("run")
.arg("--")
.arg((level - 1).to_string())
.status()
.unwrap();
}}
"#,
dylib_path_envvar(),
),
)
.build();

setenv_for_removing_empty_component(p.cargo("run -- 3"))
.with_stderr_data(str![[r#"
[COMPILING] foo v0.0.1 ([ROOT]/foo)
[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
[RUNNING] `target/debug/foo[EXE] 3`
[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
[RUNNING] `target/debug/foo[EXE] 2`
[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
[RUNNING] `target/debug/foo[EXE] 1`
[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
[RUNNING] `target/debug/foo[EXE] 0`

"#]])
.run();
}

// Regression test for #4277
#[cargo_test]
fn build_with_fake_libc_not_loading() {
Expand Down