From 753cab7c6f7a5638fd6e022eefd23a9030d32479 Mon Sep 17 00:00:00 2001
From: Martin Spiessl <33026673+MartinSpiessl@users.noreply.github.com>
Date: Mon, 2 Jan 2023 13:08:13 +0100
Subject: [PATCH] Improve support for __extension__ keyword

This keyword is allowed to appear before expressions in GNU C and
serves as a hint to the compiler to not issue a warning in
case a GNU C specific extension is used, cf.:
https://gcc.gnu.org/onlinedocs/gcc/Alternate-Keywords.html

The two additional parser rules in this commit will allow to parse
that keyword correctly when it appears before an expression.

For now, the keyword is not reproduced when code is generated from
the AST, but this should not be a problem as it is just controlling
compiler warnings and does not affect semantics (as outlined above).
---
 pycparserext/ext_c_parser.py |  8 ++++++++
 test/test_pycparserext.py    | 13 +++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/pycparserext/ext_c_parser.py b/pycparserext/ext_c_parser.py
index 5308ea6..db59694 100644
--- a/pycparserext/ext_c_parser.py
+++ b/pycparserext/ext_c_parser.py
@@ -546,6 +546,14 @@ def p_statement(self, p):
         """
         p[0] = p[1]
 
+    def p_gnu_primary_expression_7(self, p):
+        """ primary_expression : __EXTENSION__ primary_expression """
+        p[0] = p[2]
+
+    def p_gnu_assignment_expression_2(self, p):
+        """ assignment_expression : __EXTENSION__ assignment_expression """
+        p[0] = p[2]
+
     def p_attribute_const(self, p):
         """ attribute : __CONST
         """
diff --git a/test/test_pycparserext.py b/test/test_pycparserext.py
index 183769f..f349cf3 100644
--- a/test/test_pycparserext.py
+++ b/test/test_pycparserext.py
@@ -348,6 +348,19 @@ def test_lvalue_gnu_statement_expression():
     print(GnuCGenerator().visit(ast))
 
 
+def test_gnu_extension_expression():
+    src = """
+      int func(int a) {
+        int i = (4,__extension__ 2);
+        char * name = __extension__ __PRETTY_FUNCTION__;
+        i = __extension__ i++;
+        i = __extension__((__extension__ i)++ + (--(__extension__ i)));
+        return __extension__(int)__extension__({; ; i;});
+     }
+    """
+    assert _round_trip_matches(src)
+
+
 def test_empty_struct_declaration():
     src = """
         typedef struct Foo {