Auto merge of #8329 - ehuss:apple-no-hash, r=alexcrichton

Don't hash executable filenames on apple platforms.

Due to some recent changes to the backtrace crate, backtraces on apple platforms haven't been working (they are missing line/filename information). The reason is that previously libbacktrace would hunt through the directory for any matching file in the `.dSYM` directory. The new implementation expects a file matching the executable name exactly (which no longer includes the hash because Cargo renames it).

The solution here is to not include a hash in the executable filename. This matches the behavior on Windows which does it for a similar reason (paths are embedded in pdb files).

The downside is that switching between different settings (like different features) causes Cargo to rebuild the binary each time.  I don't think this is a particularly common use case, at least I've not heard any complaints about this behavior on Windows.

Fixes rust-lang/rust#72550

src/cargo/core/compiler/context/compilation_files.rs

@@ -608,6 +608,12 @@ fn should_use_metadata(bcx: &BuildContext<'_, '_>, unit: &Unit) -> bool {
     // - wasm32 executables: When using emscripten, the path to the .wasm file
     //   is embedded in the .js file, so we don't want the hash in there.
     //   TODO: Is this necessary for wasm32-unknown-unknown?
+    // - apple executables: The executable name is used in the dSYM directory
+    //   (such as `target/debug/foo.dSYM/Contents/Resources/DWARF/foo-64db4e4bf99c12dd`).
+    //   Unfortunately this causes problems with our current backtrace
+    //   implementation which looks for a file matching the exe name exactly.
+    //   See https://github.com/rust-lang/rust/issues/72550#issuecomment-638501691
+    //   for more details.
     //
     // This is only done for local packages, as we don't expect to export
     // dependencies.
@@ -622,7 +628,8 @@ fn should_use_metadata(bcx: &BuildContext<'_, '_>, unit: &Unit) -> bool {
     if (unit.target.is_dylib()
         || unit.target.is_cdylib()
         || (unit.target.is_executable() && short_name.starts_with("wasm32-"))
-        || (unit.target.is_executable() && short_name.contains("msvc")))
+        || (unit.target.is_executable() && short_name.contains("msvc"))
+        || (unit.target.is_executable() && short_name.contains("-apple-")))
         && unit.pkg.package_id().source_id().is_path()
         && env::var("__CARGO_DEFAULT_LIB_METADATA").is_err()
     {

tests/testsuite/build.rs

@@ -4149,7 +4149,7 @@ fn uplift_dsym_of_bin_on_mac() {
     assert!(p.target_debug_dir().join("foo.dSYM").is_dir());
     assert!(p.target_debug_dir().join("b.dSYM").is_dir());
     assert!(p.target_debug_dir().join("b.dSYM").is_symlink());
-    assert!(p.target_debug_dir().join("examples/c.dSYM").is_symlink());
+    assert!(p.target_debug_dir().join("examples/c.dSYM").is_dir());
     assert!(!p.target_debug_dir().join("c.dSYM").exists());
     assert!(!p.target_debug_dir().join("d.dSYM").exists());
 }

tests/testsuite/collisions.rs

@@ -91,9 +91,9 @@ This may become a hard error in the future; see <https://github.com/rust-lang/ca
 }
 
 #[cargo_test]
-// --out-dir and examples are currently broken on MSVC.
+// --out-dir and examples are currently broken on MSVC and apple.
 // See https://github.com/rust-lang/cargo/issues/7493
-#[cfg(not(target_env = "msvc"))]
+#[cfg_attr(any(target_env = "msvc", target_vendor = "apple"), ignore)]
 fn collision_export() {
     // `--out-dir` combines some things which can cause conflicts.
     let p = project()

tests/testsuite/freshness.rs

@@ -491,8 +491,8 @@ fn changing_bin_features_caches_targets() {
     /* Targets should be cached from the first build */
 
     let mut e = p.cargo("build");
-    // MSVC does not include hash in binary filename, so it gets recompiled.
-    if cfg!(target_env = "msvc") {
+    // MSVC/apple does not include hash in binary filename, so it gets recompiled.
+    if cfg!(any(target_env = "msvc", target_vendor = "apple")) {
         e.with_stderr("[COMPILING] foo[..]\n[FINISHED] dev[..]");
     } else {
         e.with_stderr("[FINISHED] dev[..]");
@@ -501,7 +501,7 @@ fn changing_bin_features_caches_targets() {
     p.rename_run("foo", "off2").with_stdout("feature off").run();
 
     let mut e = p.cargo("build --features foo");
-    if cfg!(target_env = "msvc") {
+    if cfg!(any(target_env = "msvc", target_vendor = "apple")) {
         e.with_stderr("[COMPILING] foo[..]\n[FINISHED] dev[..]");
     } else {
         e.with_stderr("[FINISHED] dev[..]");