I tried with a SimpleType struct, an int, and the field in the base class is set correctly.

With a Vala struct then the field in the object is not set at all - I'm getting random numbers. So it could be failing when chaining up in the constructor with a struct type as an argument. I've not tried an object instance type.

Looking at C code from the following test case:

void main () {
	var initialized_test_struct = IncrementByOneStruct (20);
	assert_true (initialized_test_struct.value == 21);

	var test_object = new Test(initialized_test_struct);
	assert_true (test_object.my_field.value == 21);
}

public struct IncrementByOneStruct {
	int value;

	IncrementByOneStruct (int value) {
		this.value = value + 1;
	}
}

public class BaseTest {
	public IncrementByOneStruct my_field;

	BaseTest (IncrementByOneStruct value) {
		my_field = value;
	}
}

public class Test:BaseTest {
	public Test (IncrementByOneStruct value) {
		base (value);
	}
}

The code generated for the Test constructor shows the temporary variable is assigned to 'value' after the chain up occurs:

Test*
test_construct (GType object_type, 
                IncrementByOneStruct* value)
{
        Test* self = NULL;
        IncrementByOneStruct _tmp0_;
        g_return_val_if_fail (value != NULL, NULL);
        self = (Test*) base_test_construct (object_type, &_tmp0_);
        _tmp0_ = *value;
        return self;
}

Created attachment 365806 [details] [review]
codegen: Fix chain-up regression with real non-null struct parameters

Regression of b9035aaf17a9a97a070812a8ee83251fd3893b1e

Attachment 365806 [details] pushed as 60563fc - codegen: Fix chain-up regression with real non-null struct parameters