Skip extra tokens after `#include "..."`

chibicc.h

@@ -77,6 +77,7 @@ struct Token {
 void error(char *fmt, ...);
 void error_at(char *loc, char *fmt, ...);
 void error_tok(Token *tok, char *fmt, ...);
+void warn_tok(Token *tok, char *fmt, ...);
 bool equal(Token *tok, char *op);
 Token *skip(Token *tok, char *op);
 bool consume(Token **rest, Token *tok, char *str);

preprocess.c

@@ -4,6 +4,17 @@ static bool is_hash(Token *tok) {
   return tok->at_bol && equal(tok, "#");
 }
 
+// Some preprocessor directives such as #include allow extraneous
+// tokens before newline. This function skips such tokens.
+static Token *skip_line(Token *tok) {
+  if (tok->at_bol)
+    return tok;
+  warn_tok(tok, "extra token");
+  while (tok->at_bol)
+    tok = tok->next;
+  return tok;
+}
+
 static Token *copy_token(Token *tok) {
   Token *t = calloc(1, sizeof(Token));
   *t = *tok;
@@ -51,7 +62,8 @@ static Token *preprocess2(Token *tok) {
       Token *tok2 = tokenize_file(path);
       if (!tok2)
         error_tok(tok, "%s", strerror(errno));
-      tok = append(tok2, tok->next);
+      tok = skip_line(tok->next);
+      tok = append(tok2, tok);
       continue;
     }
 

tokenize.c

@@ -65,6 +65,13 @@ void error_tok(Token *tok, char *fmt, ...) {
   exit(1);
 }
 
+void warn_tok(Token *tok, char *fmt, ...) {
+  va_list ap;
+  va_start(ap, fmt);
+  verror_at(tok->file->name, tok->file->contents, tok->line_no, tok->loc, fmt, ap);
+  va_end(ap);
+}
+
 // Consumes the current token if it matches `op`.
 bool equal(Token *tok, char *op) {
   return memcmp(tok->loc, op, tok->len) == 0 && op[tok->len] == '\0';