diff --git a/cxxheaderparser/lexer.py b/cxxheaderparser/lexer.py
index 17caf92..28839d9 100644
--- a/cxxheaderparser/lexer.py
+++ b/cxxheaderparser/lexer.py
@@ -73,6 +73,7 @@ class PlyLexer:
         "alignas",
         "alignof",
         "asm",
+        "__asm",
         "auto",
         "bool",
         "break",
@@ -99,6 +100,7 @@ class PlyLexer:
         "enum",
         "explicit",
         "export",
+        "__extension__",
         "extern",
         "false",
         "final",
@@ -124,6 +126,7 @@ class PlyLexer:
         "public",
         "register",
         "reinterpret_cast",
+        "__restrict",
         "requires",
         "return",
         "short",
diff --git a/cxxheaderparser/parser.py b/cxxheaderparser/parser.py
index 7cea0ea..76a04d1 100644
--- a/cxxheaderparser/parser.py
+++ b/cxxheaderparser/parser.py
@@ -302,6 +302,7 @@ def parse(self) -> None:
         ] = {
             "__attribute__": self._consume_gcc_attribute,
             "__declspec": self._consume_declspec,
+            "__extension__": lambda _1, _2: None,
             "alignas": self._consume_attribute_specifier_seq,
             "extern": self._parse_extern,
             "friend": self._parse_friend_decl,
@@ -879,6 +880,12 @@ def _parse_requires_segment(
             # Let the caller decide
             return tok
 
+    def _consume_asm(
+        self, tok: LexToken, doxygen: typing.Optional[str] = None
+    ) -> None:
+        tok = self._next_token_must_be("(")
+        self._consume_balanced_tokens(tok)
+
     #
     # Attributes
     #
@@ -1394,8 +1401,15 @@ def _discard_ctor_initializer(self) -> None:
 
     def _parse_bitfield(self) -> int:
         # is a integral constant expression... for now, just do integers
-        tok = self._next_token_must_be("INT_CONST_DEC")
-        return int(tok.value)
+        const_expr = ''
+        while True:
+            tok = self.lex.token_if_not("=", ";")
+            if tok:
+                const_expr += tok.value
+            else:
+                break
+
+        return int(eval(const_expr))
 
     def _parse_field(
         self,
@@ -1791,6 +1805,9 @@ def _parse_parameter(
 
         dtype = self._parse_cv_ptr(parsed_type)
 
+        # optional __restrict
+        tok = self.lex.token_if("__restrict")
+
         # optional parameter pack
         if self.lex.token_if("ELLIPSIS"):
             param_pack = True
@@ -2679,6 +2696,15 @@ def _parse_declarations(
             # Unset the doxygen, location
             doxygen = None
 
+            tok = self.lex.token_if("__asm")
+            if tok:
+                self._consume_asm(tok)
+
+            tok = self.lex.token_if_in_set(self._attribute_start_tokens)
+            while tok:
+                self._consume_attribute(tok)
+                tok = self.lex.token_if_in_set(self._attribute_start_tokens)
+
             # Check for multiple declarations
             tok = self._next_token_must_be(",", ";")
             location = tok.location