Work-around macOS 10.15 Gatekeeper issue.

Author: ehuss

crates/cargo-test-support/src/lib.rs

@@ -1741,6 +1741,10 @@ fn _process(t: &OsStr) -> cargo::util::ProcessBuilder {
         .env_remove("GIT_COMMITTER_NAME")
         .env_remove("GIT_COMMITTER_EMAIL")
         .env_remove("MSYSTEM"); // assume cmd.exe everywhere on windows
+    if cfg!(target_os = "macos") {
+        // Work-around a bug in macOS 10.15, see `link_or_copy` for details.
+        p.env("__CARGO_COPY_DONT_LINK_DO_NOT_USE_THIS", "1");
+    }
     p
 }
 

src/cargo/util/paths.rs

@@ -379,7 +379,20 @@ fn _link_or_copy(src: &Path, dst: &Path) -> CargoResult<()> {
         };
         symlink(src, dst)
     } else {
-        fs::hard_link(src, dst)
+        if env::var_os("__CARGO_COPY_DONT_LINK_DO_NOT_USE_THIS").is_some() {
+            // This is a work-around for a bug in macOS 10.15. When running on
+            // APFS, there seems to be a strange race condition with
+            // Gatekeeper where it will forcefully kill a process launched via
+            // `cargo run` with SIGKILL. Copying seems to avoid the problem.
+            // This shouldn't affect anyone except Cargo's test suite because
+            // it is very rare, and only seems to happen under heavy load and
+            // rapidly creating lots of executables and running them.
+            // See https://github.com/rust-lang/cargo/issues/7821 for the
+            // gory details.
+            fs::copy(src, dst).map(|_| ())
+        } else {
+            fs::hard_link(src, dst)
+        }
     };
     link_result
         .or_else(|err| {