Assert only final rustc

Author: Mark-Simulacrum

collector/src/execute.rs

@@ -310,6 +310,10 @@ impl<'a> CargoProcess<'a> {
             // we want to wrap rustc.
             if let Some((ref mut processor, ..)) = self.processor_etc {
                 let profiler = processor.profiler(self.build_kind).name();
+                // If we're using a processor, we expect that only the crate
+                // we're interested in benchmarking will be built, not any
+                // dependencies.
+                cmd.env("EXPECT_ONLY_WRAPPED_RUSTC", "1");
                 cmd.arg("--wrap-rustc-with");
                 cmd.arg(profiler);
                 cmd.args(&self.rustc_args);

collector/src/rustc-fake.rs

@@ -215,6 +215,12 @@ fn main() {
             }
         }
     } else {
+        if env::var_os("EXPECT_ONLY_WRAPPED_RUSTC").is_some() {
+            eprintln!("{:?} {:?}", tool, args);
+            eprintln!("exiting -- non-wrapped rustc");
+            std::process::exit(1);
+        }
+
         let mut cmd = Command::new(&tool);
         cmd.args(&args);
         exec(&mut cmd);