Output warnings for non-UTF-8 tokens.

bindgen/ir/context.rs

@@ -2162,7 +2162,14 @@ If you encounter an error missing from this list, please file an issue or a PR!"
             let spelling = token.spelling();
             let name = match spelling.to_str() {
                 Ok(name) => Cow::Borrowed(name),
-                Err(_) => spelling.to_string_lossy(),
+                Err(_) => {
+                    let name = spelling.to_string_lossy();
+                    warn!(
+                        "Lossy conversion of non-UTF8 token {:?} to {:?}.",
+                        spelling, name
+                    );
+                    name
+                }
             };
             match name.as_ref() {
                 "inline" => {

bindgen/ir/var.rs

@@ -167,17 +167,21 @@ fn handle_function_macro(
         t.kind == clang_sys::CXToken_Punctuation &&
             t.spelling().to_bytes() == b")"
     };
-    let tokens: Vec<_> = cursor.tokens().iter().collect();
-    if let Some(boundary) = tokens.iter().position(is_closing_paren) {
-        let tokens: Result<Vec<_>, _> = tokens
+    let mut raw_tokens: Vec<_> = cursor.tokens().iter().collect();
+    if let Some(boundary) = raw_tokens.iter().position(is_closing_paren) {
+        let tokens: Result<Vec<_>, _> = raw_tokens
             .iter()
             .map(|token| token.spelling().to_str())
             .collect();
 
         let mut tokens = if let Ok(tokens) = tokens {
             tokens
         } else {
-            // Skip macros containing invalid UTF-8.
+            let raw_name = raw_tokens.remove(0);
+            warn!(
+                "Ignoring macro {:?} containing invalid UTF-8 tokens.",
+                raw_name.spelling()
+            );
             return;
         };