c_parser: support parenthesized compounds (#423)

* c_parser: support parenthesized compounds

Support parenthesized compound statements as described here:
    https://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html

Signed-off-by: Jordan Yates <jordan.yates@data61.csiro.au>

* test_c_parser: support additional initializers

Add support to `expand_init` for additional `c_ast` types. If a type
is not explicitly handled, return the type name instead of `None`.

Signed-off-by: Jordan Yates <jordan.yates@data61.csiro.au>

* test_c_parser: test parenthesized compounds

Add parsing tests for various situations of parenthesized compound
statements. The complete tree generated by the test string is:

```
FileAST:
  FuncDef:
    Decl: foo, [], [], []
      FuncDecl:
        TypeDecl: foo, []
          IdentifierType: ['void']
    Compound:
      Decl: a, [], [], []
        TypeDecl: a, []
          IdentifierType: ['int']
      Compound:
      Compound:
        Constant: int, 1
      Compound:
        Constant: int, 1
        Constant: int, 2
      Decl: b, [], [], []
        TypeDecl: b, []
          IdentifierType: ['int']
        Compound:
          Constant: int, 1
      Decl: c, [], [], []
        TypeDecl: c, []
          IdentifierType: ['int']
      Decl: d, [], [], []
        TypeDecl: d, []
          IdentifierType: ['int']
        Compound:
          Decl: x, [], [], []
            TypeDecl: x, []
              IdentifierType: ['int']
            Constant: int, 1
          BinaryOp: +
            ID: x
            Constant: int, 2
      Assignment: =
        ID: a
        Compound:
          Decl: x, [], [], []
            TypeDecl: x, []
              IdentifierType: ['int']
            Constant: int, 1
          BinaryOp: *
            Constant: int, 2
            ID: x
```

Signed-off-by: Jordan Yates <jordan.yates@data61.csiro.au>

pycparser/c_parser.py

@@ -1564,6 +1564,10 @@ def p_expression(self, p):
             p[1].exprs.append(p[3])
             p[0] = p[1]
 
+    def p_parenthesized_compound_expression(self, p):
+        """ assignment_expression : LPAREN compound_statement RPAREN """
+        p[0] = p[2]
+
     def p_typedef_name(self, p):
         """ typedef_name : TYPEID """
         p[0] = c_ast.IdentifierType([p[1]], coord=self._token_coord(p, 1))

tests/test_c_parser.py

@@ -85,8 +85,20 @@ def expand_init(init):
         return ['Constant', init.type, init.value]
     elif typ == ID:
         return ['ID', init.name]
+    elif typ == Decl:
+        return ['Decl', init.name]
     elif typ == UnaryOp:
         return ['UnaryOp', init.op, expand_decl(init.expr)]
+    elif typ == BinaryOp:
+        return ['BinaryOp', expand_init(init.left), init.op, expand_init(init.right)]
+    elif typ == Compound:
+        blocks = []
+        if init.block_items:
+            blocks = [expand_init(i) for i in init.block_items]
+        return ['Compound', blocks]
+    else:
+        # Fallback to type name
+        return [typ.__name__]
 
 
 class TestCParser_base(unittest.TestCase):
@@ -612,6 +624,47 @@ def test_compound_literals(self):
                 ([['ID', 'a']], [['Constant', 'int', '1'], ['Constant', 'int', '2']]),
                 ([['ID', 'b'], ['Constant', 'int', '0']], ['ID', 't'])])
 
+    def test_parenthesized_compounds(self):
+        e = self.parse(r'''
+        void foo() {
+         	int a;
+            ({});
+            ({ 1; });
+            ({ 1; 2; });
+            int b = ({ 1; });
+            int c, d = ({ int x = 1; x + 2; });
+            a = ({ int x = 1; 2 * x; });   
+        }''')
+        body = e.ext[0].body.block_items
+
+        self.assertIsInstance(body[1], Compound)
+        self.assertEqual(body[1].block_items, None)
+
+        self.assertIsInstance(body[2], Compound)
+        self.assertEqual(len(body[2].block_items), 1)
+        self.assertIsInstance(body[2].block_items[0], Constant)
+
+        self.assertIsInstance(body[3], Compound)
+        self.assertEqual(len(body[3].block_items), 2)
+        self.assertIsInstance(body[3].block_items[0], Constant)
+        self.assertIsInstance(body[3].block_items[1], Constant)
+
+        self.assertIsInstance(body[4], Decl)
+        self.assertEqual(expand_init(body[4].init),
+            ['Compound', [['Constant', 'int', '1']]])
+
+        self.assertIsInstance(body[5], Decl)
+        self.assertEqual(body[5].init, None)
+
+        self.assertIsInstance(body[6], Decl)
+        self.assertEqual(expand_init(body[6].init),
+            ['Compound', [['Decl', 'x'], ['BinaryOp', ['ID', 'x'], '+', ['Constant', 'int', '2']]]])
+
+        self.assertIsInstance(body[7], Assignment)
+        self.assertIsInstance(body[7].rvalue, Compound)
+        self.assertEqual(expand_init(body[7].rvalue),
+            ['Compound', [['Decl', 'x'], ['BinaryOp', ['Constant', 'int', '2'], '*', ['ID', 'x']]]])
+
     def test_enums(self):
         e1 = "enum mycolor op;"
         e1_type = self.parse(e1).ext[0].type.type