Ok, there was a bug in my code but the reaction of vala is curious. My code
did something like this:
public class Foo
{
int i;
public Foo.from(int i)
{
this.i = i;
}
}
public class Bar
{
Foo f;
public Bar()
{
assert( this != null );
f.from(1); // this line causes the trouble
}
}
int main(string[] argv)
{
var b = new Bar();
return 0;
}
This program fails in the following way:
**
ERROR:/net/tieto/home/vkirsan/sandbit/test.vala.c:305:bar_construct:
assertion failed: (this != null)
Abort
And vala generates the following interesting piece of code:
Bar* bar_construct (GType object_type) {
Bar* self = NULL;
Foo* _tmp0_ = NULL;
_vala_assert (self != NULL, "this != null");
_tmp0_ = self->priv->f;
self = (Bar*) foo_construct_from (object_type, 1);
return self;
}
So it looks like vala, compiling a constructor for a class, treats direct
calling constructor(s) of the object's field(s) as an instruction to
construct the object itself.
*Is it ok?* Or does it rather look like a bug?
Sorry, if I may not explain clearly enough, I'm no native speaker.
BR, Vitaly Kirsanov
skype: vkirsan
2014-11-11 13:52 GMT+03:00 Виталий Кирсанов <[email protected]>:
> Hm, the following code works fine indeed:
>
> public class Foo
> {
> public Foo()
> {
> assert( this != null );
> }
> }
>
> int main(string[] argv)
> {
> var f = new Foo();
> return 0;
> }
>
>
> But in my other real program a similar assertion is false in a
> constructor. I need dig to the bottom of it, will be back with results.
>
> BR, Vitaly Kirsanov
> skype: vkirsan
>
> 2014-11-11 3:37 GMT+03:00 Nor Jaidi Tuah <[email protected]>:
>
>>
>> > Is 'this' always null in constructors? The following code produces a
>> > run-time error:
>> >
>> > public class Foo
>> > {
>> > Foo()
>> > {
>> > assert( this != null );
>> > }
>> > }
>>
>> Are you sure about this? Perhaps you should
>> provide a small program that triggers this error.
>>
>> > Is there a way to get the true value of this in the constructor? I
>> guess,
>> > probably not. As far as I understand references in vala are somewhat
>> > similar to shared_ptr<> pointers in C++ and vala classes to
>> > enable_shared_from_this<> C++ subclasses. If the reasons are also
>> similar,
>> > it would be sad.
>>
>> Vala references are like C pointers -- raw,
>> unwrapped, direct and optimizer friendly (though
>> I notice that the vala compiler puts an
>> additional indirection for private variables,
>> incurring performance penalty in object construction
>> and subsequent accesses).
>>
>> C++ shared_ptr is an ugly wart. Its only similarity
>> with Vala references is ref counting.
>>
>> Do not let your experience with shared_ptr
>> discourage you from Vala.
>>
>> Nice day
>> Nor Jaidi Tuah
>>
>>
>>
>>
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