fix nested anonymous union offset

Author: andreax79

cstruct/c_parser.py

@@ -426,6 +426,10 @@ def parse_struct(
             for nested_field_name, nested_field_type in field_type.ref.__fields_types__.items():
                 if nested_field_name in fields_types:
                     raise ParserError(f"Duplicate member `{nested_field_name}`")
+                # set the corret offset
+                nested_field_type = nested_field_type.copy()
+                nested_field_type.base_offset = offset + nested_field_type.base_offset
+                nested_field_type.offset = offset + nested_field_type.offset
                 fields_types[nested_field_name] = nested_field_type
             vname = f"__anonymous{anonymous}"
             anonymous += 1

tests/test_nested.py

@@ -259,3 +259,69 @@ def test_nested_struct_offset():
     assert o.pack() == b'ciao_ciao\x00\x00\xbc\x08\xe4\xb0\x0cX4\xe6\x07\x00\x003333'
     assert o.u1.pack() == b'\xe6\x07\x00\x00'
     assert o.aaa.pack() == b'3333'
+
+
+def test_nested_anonymous_struct_offset():
+    cstruct.parse(
+        """
+        struct op_a1 {
+          int a;
+        };
+
+        struct op_b1 {
+          char a;
+          char b;
+          char c;
+        };
+    """,
+        __byte_order__=cstruct.LITTLE_ENDIAN,
+    )
+
+    Opu = cstruct.parse(
+        """
+        struct opu {
+          char preamble[10];
+          uint64_t magic;
+          union {
+            struct op_a1 a_op;
+            struct op_b1 b_op;
+          };
+          struct op_a aaa;
+        };
+    """,
+        __byte_order__=cstruct.LITTLE_ENDIAN,
+    )
+
+    o = Opu()
+    o.preamble = b'ciao_ciao'
+    o.magic = 3771778641802345472
+    o.__anonymous0.a_op.a = 2022
+    o.aaa.a = 0x33333333
+    assert o.__anonymous0.b_op.a == b'\xe6'
+    assert o.__anonymous0.b_op.b == b'\x07'
+    assert o.__anonymous0.b_op.c == b'\x00'
+    assert o.__base__ == 0
+    assert o.__anonymous0.__base__ >= 10
+    assert o.__anonymous0.__base__ == o.__anonymous0.a_op.__base__
+    assert o.__anonymous0.__base__ == o.__anonymous0.b_op.__base__
+    assert o.aaa.__base__ > o.__anonymous0.__base__
+    assert o.pack() == b'ciao_ciao\x00\x00\xbc\x08\xe4\xb0\x0cX4\xe6\x07\x00\x003333'
+    assert o.__anonymous0.pack() == b'\xe6\x07\x00\x00'
+    assert o.aaa.pack() == b'3333'
+
+    o = Opu()
+    o.preamble = b'ciao_ciao'
+    o.magic = 3771778641802345472
+    o.a_op.a = 2022
+    o.aaa.a = 0x33333333
+    assert o.b_op.a == b'\xe6'
+    assert o.b_op.b == b'\x07'
+    assert o.b_op.c == b'\x00'
+    assert o.__base__ == 0
+    assert o.__anonymous0.__base__ >= 10
+    assert o.__anonymous0.__base__ == o.a_op.__base__
+    assert o.__anonymous0.__base__ == o.b_op.__base__
+    assert o.aaa.__base__ > o.__base__
+    assert o.pack() == b'ciao_ciao\x00\x00\xbc\x08\xe4\xb0\x0cX4\xe6\x07\x00\x003333'
+    assert o.a_op.pack() == b'\xe6\x07\x00\x00'
+    assert o.aaa.pack() == b'3333'