Some cleanup

Author: Aaron1011

src/bin/cargo-miri.rs

@@ -84,40 +84,31 @@ fn get_arg_flag_value(name: &str) -> Option<String> {
     }
 }
 
-fn is_build_dep(mut args: impl Iterator<Item = String>) -> bool {
-    //eprintln!("Out dir: {:?}", std::env::var("OUT_DIR"));
-    args.any(|arg| arg.starts_with("--emit=") && arg.contains("link"))
+
+/// Determines if we are being invoked (as rustc) to build a runnable
+/// executable. We run "cargo check", so this should only happen when
+/// we are trying to compile a build script or build script dependency,
+/// which actually needs to be executed on the host platform.
+///
+/// Currently, we detect this by checking for "--emit=link",
+/// which indicates that Cargo instruced rustc to output
+/// a native object.
+fn is_build_dep() -> bool {
+    std::env::args().any(|arg| arg.starts_with("--emit=") && arg.contains("link"))
 }
 
-// Returns whether or not Cargo invoked the wrapper (this binary) to compile
-// the final, target crate (either a test for 'cargo test', or a binary for 'cargo run')
-// Right now, this is an awful hack that checks several different pieces of information
-// to try to figure out if the crate being compiled is the right one.
-// Ideally, Cargo would set en environment variable indicating whether or
-// not the wrapper is being invoked on the target crate.
-// For now, this is the best we can do
+/// Returns whether or not Cargo invoked the wrapper (this binary) to compile
+/// the final, target crate (either a test for 'cargo test', or a binary for 'cargo run')
+/// Cargo does not give us this information directly, so we need to check
+/// various command-line flags.
 fn is_target_crate(is_build_script: bool) -> bool {
-    //eprintln!("Args: {:?}", std::env::args().collect::<Vec<_>>());
     let is_bin = get_arg_flag_value("--crate-type").as_deref() == Some("bin");
     let is_test = std::env::args().find(|arg| arg == "--test").is_some();
-    (is_bin || is_test) && !is_build_script
-    // Cargo sets this to the directory containing the manifest of the crate
-    // the wrapper is being invoekd to compile. This should be unique
-    // across the entire build (except for build scripts, which we handle below).
-    // We cannot check the crate name, since this may not be unique
-    // (e.g. if the build contains multiple versions of the same crate,
-    // or the same crate from multiple sources)
-    //let manifest_dir = std::env::var("CARGO_MANIFEST_DIR").ok();
-
-    // The manifest directory for our target crate. This is set by `cargo-miri`
-    // (the original invoation by the user) by using `cargo_metadata` to locate
-    // the manifest.
-    //let expected_dir = std::env::var("MIRI_MAGIC_DIR").expect("MIRI_MAGIC_DIR not set!");
-
-    //manifest_dir == Some(expected_dir) && !is_build_script
-    //
-    //false
 
+    // The final runnable (under Miri) crate will either be a binary crate
+    // or a test crate. We make sure to exclude build scripts here, since
+    // they are also build with "--crate-type bin"
+    (is_bin || is_test) && !is_build_script
 }