added __alignof__ gnu extension support (#84)

* added __alignof__ gnu extension support

* fix for linter

* feat: Add __alignof__ support to generator and round-trip test

This commit adds support for the `__alignof__` GNU extension to the C code generator. It also includes a round-trip test to verify that the generator correctly handles the `__alignof__` keyword.

---------

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>

Author: retif

pycparserext/ext_c_generator.py

@@ -16,6 +16,8 @@ def visit_UnaryOp(self, n):
             # Always parenthesize the argument of sizeof since it can be
             # a name.
             return "sizeof(%s)" % self.visit(n.expr)
+        elif n.op == "__alignof__":
+            return "__alignof__(%s)" % self.visit(n.expr)
         else:
             # avoid merging of "- - x" or "__real__varname"
             return "%s %s" % (n.op, operand)

pycparserext/ext_c_lexer.py

@@ -74,7 +74,8 @@ def add_lexer_keywords(cls, keywords):
     "__restrict__", "__restrict",
     "__inline__", "__inline",
     "__extension__",
-    "__volatile", "__volatile__"]
+    "__volatile", "__volatile__",
+    "__alignof__"]
 
 add_lexer_keywords(GnuCLexer, _COMMON_KEYWORDS + _GNU_KEYWORDS)
 

pycparserext/ext_c_parser.py

@@ -549,6 +549,14 @@ def p_gnu_primary_expression_6(self, p):
         """ primary_expression : gnu_statement_expression """
         p[0] = p[1]
 
+    def p_gnu_unary_expression(self, p):
+        """ unary_expression : __ALIGNOF__ LPAREN type_name RPAREN
+        """
+        p[0] = c_ast.UnaryOp(
+            p[1],
+            p[2] if len(p) == 3 else p[3],
+            self._token_coord(p, 1))
+
     def p_statement(self, p):
         """ statement   : labeled_statement
                         | expression_statement

test/test_pycparserext.py

@@ -571,6 +571,11 @@ def visit_FuncDeclExt(self, node):
         assert visit_num[0] == visit_num[1], assert_msg
 
 
+def test_alignof():
+    src = "int x = __alignof__(int);"
+    assert _round_trip_matches(src)
+
+
 def test_typeof_reproduction():
     src = """
     int func(int a, int b) {