xargs: reject quotes spanning input lines

src/xargs/mod.rs

@@ -618,6 +618,12 @@ where
 
             match (&escape, pending[i]) {
                 (Some(Escape::Quote(quote)), c) if c == *quote => escape = None,
+                (Some(Escape::Quote(q)), b'\n') => {
+                    return Err(io::Error::new(
+                        io::ErrorKind::InvalidInput,
+                        format!("Unterminated quote: {q}"),
+                    ));
+                }
                 (Some(Escape::Quote(_)), c) => result.push(c),
                 (Some(Escape::Slash), c) => {
                     result.push(c);

tests/test_xargs.rs

@@ -390,6 +390,25 @@ fn xargs_unterminated_quote() {
         .no_stdout();
 }
 
+#[test]
+fn xargs_quotes_cannot_span_lines() {
+    let temp_file = tempfile::NamedTempFile::new().unwrap();
+
+    for quote in ['\'', '"'] {
+        std::fs::write(
+            temp_file.path(),
+            format!("alpha{quote}beta\ngamma{quote}\n"),
+        )
+        .unwrap();
+
+        ucmd()
+            .args(&["-a", &temp_file.path().to_string_lossy()])
+            .fails_with_code(1)
+            .stderr_contains("Error: Unterminated quote:")
+            .no_stdout();
+    }
+}
+
 #[test]
 fn xargs_zero_lines() {
     ucmd()