Fix ICE when reading non-UTF-8 input from stdin

Fixes #22387.

src/librustc_driver/lib.rs

@@ -456,10 +456,13 @@ pub fn run_compiler<'a>(args: &[String],
                                            None);
 
     let (odir, ofile) = make_output(&matches);
-    let (input, input_file_path) = match make_input(&matches.free) {
-        Some((input, input_file_path)) => callbacks.some_input(input, input_file_path),
+    let (input, input_file_path, input_err) = match make_input(&matches.free) {
+        Some((input, input_file_path, input_err)) => {
+            let (input, input_file_path) = callbacks.some_input(input, input_file_path);
+            (input, input_file_path, input_err)
+        },
         None => match callbacks.no_input(&matches, &sopts, &cfg, &odir, &ofile, &descriptions) {
-            Some((input, input_file_path)) => (input, input_file_path),
+            Some((input, input_file_path)) => (input, input_file_path, None),
             None => return (Ok(()), None),
         },
     };
@@ -470,6 +473,13 @@ pub fn run_compiler<'a>(args: &[String],
         sopts, input_file_path.clone(), descriptions, codemap, emitter_dest,
     );
 
+    if let Some(err) = input_err {
+        // Immediately stop compilation if there was an issue reading
+        // the input (for example if the input stream is not UTF-8).
+        sess.err(&format!("{}", err));
+        return (Err(CompileIncomplete::Stopped), Some(sess));
+    }
+
     let trans = get_trans(&sess);
 
     rustc_lint::register_builtins(&mut sess.lint_store.borrow_mut(), Some(&sess));
@@ -512,17 +522,22 @@ fn make_output(matches: &getopts::Matches) -> (Option<PathBuf>, Option<PathBuf>)
 }
 
 // Extract input (string or file and optional path) from matches.
-fn make_input(free_matches: &[String]) -> Option<(Input, Option<PathBuf>)> {
+fn make_input(free_matches: &[String]) -> Option<(Input, Option<PathBuf>, Option<io::Error>)> {
     if free_matches.len() == 1 {
         let ifile = &free_matches[0];
         if ifile == "-" {
             let mut src = String::new();
-            io::stdin().read_to_string(&mut src).unwrap();
+            let err = if io::stdin().read_to_string(&mut src).is_err() {
+                Some(io::Error::new(io::ErrorKind::InvalidData,
+                                    "couldn't read from stdin, as it did not contain valid UTF-8"))
+            } else {
+                None
+            };
             Some((Input::Str { name: FileName::Anon, input: src },
-                  None))
+                  None, err))
         } else {
             Some((Input::File(PathBuf::from(ifile)),
-                  Some(PathBuf::from(ifile))))
+                  Some(PathBuf::from(ifile)), None))
         }
     } else {
         None

src/test/run-make/stdin-non-utf8/Makefile

@@ -0,0 +1,5 @@
+-include ../tools.mk
+
+all:
+	echo '\xD2' | $(RUSTC) - 2>&1 \
+		| $(CGREP) "error: couldn't read from stdin, as it did not contain valid UTF-8"