fix(lexer): memory leaks

src/lexer/lexer.c

@@ -35,16 +35,16 @@ static void update_last_token(struct token *tok)
 
 /* @brief: updates the current position in the stream.
  *          [stream] += [i]
- *          Also saves the last token sent (so we can free it afterwards).
- *          Also sets the current token to NULL.
+ *        Also frees the last sent token, and sets it to current_token.
+ *        Current token is then set to NULL.
  *        This function is called by token_pop().
  */
-static void save_state(char *stream, ssize_t i, struct token *tok)
+static void save_state(char *stream, ssize_t i)
 {
     remaining_chars -= i;
     end_last_token = stream + i;
 
-    update_last_token(tok);
+    update_last_token(current_token);
     update_current_token(NULL);
 }
 
@@ -156,6 +156,10 @@ static void set_token_keyword(struct token *tok, char *begin, ssize_t size)
         tok->type = TOKEN_ELIF;
     }
 
+    // no keywords found.
+    if (tok->type == TOKEN_NULL)
+        return;
+
     tok->data = calloc(size + 1, sizeof(char));
     if (tok->data == NULL)
         return;
@@ -254,9 +258,11 @@ struct token *peek_token(void)
 
 struct token *pop_token(void)
 {
-    if (last_token != NULL && last_token->type == TOKEN_EOF)
+    if (current_token != NULL && current_token->type == TOKEN_EOF)
     {
+        // we reached end of input, frees all the token still allocated.
         free_token(&last_token);
+        free_token(&current_token);
         return NULL;
     }
     char *stream = stream_init();
@@ -278,8 +284,13 @@ struct token *pop_token(void)
         i++;
     }
 
-    struct token *tok = new_token(stream, i);
-    save_state(stream, i, tok);
-
-    return tok;
+    // just in case peek() was not called before poping.
+    // (this should never happen)
+    if (current_token == NULL)
+    {
+        current_token = new_token(stream, i);
+    }
+    save_state(stream, i);
+
+    return last_token;
 }