Add Dart_Null, Dart_True, and Dart_False.

Add Dart_Null, Dart_True, and Dart_False.

Fix Dart_NewPersistentHandle so it won't break if passed one of these
persistent handles.

Reviewer: Should I document that these new functions return a
persistent handle?

[turnidge, 2011-11-03 20:54:27]

http://codereview.chromium.org/8446009/diff/1/runtime/vm/dart_api_impl.cc
File runtime/vm/dart_api_impl.cc (right):

http://codereview.chromium.org/8446009/diff/1/runtime/vm/dart_api_impl.cc#new...
runtime/vm/dart_api_impl.cc:664: return value ? Api::True() : Api::False();
How do you feel about this?  Does it violate expectation to be returning a
persistent handle here?  It is mostly transparent to the user.

[siva, 2011-11-03 21:45:25]

LGTM once the Delete issue is addressed.

http://codereview.chromium.org/8446009/diff/1/runtime/include/dart_api.h
File runtime/include/dart_api.h (right):

http://codereview.chromium.org/8446009/diff/1/runtime/include/dart_api.h#newc...
runtime/include/dart_api.h:141: DART_EXPORT Dart_Handle
Dart_NewPersistentHandle(Dart_Handle object);
What is the use case for creating a new persistent handle from another
persistent handle?
Seems like clone functionality.

http://codereview.chromium.org/8446009/diff/1/runtime/vm/dart_api_impl.cc
File runtime/vm/dart_api_impl.cc (right):

http://codereview.chromium.org/8446009/diff/1/runtime/vm/dart_api_impl.cc#new...
runtime/vm/dart_api_impl.cc:664: return value ? Api::True() : Api::False();
I think this is fine the only thing we may have to do is to protect ourselves
from somebody calling Dart_DeletePersistentHandle(...) on these handles (null,
true, false). 

Maybe delete is a nop when these handles are passed in.

On 2011/11/03 20:54:27, turnidge wrote:
> How do you feel about this?  Does it violate expectation to be returning a
> persistent handle here?  It is mostly transparent to the user.

http://codereview.chromium.org/8446009/diff/1/runtime/vm/dart_api_impl.cc#new...
runtime/vm/dart_api_impl.cc:669: bool* value) {
Instead of this function does it make sense to have a Dart_IsTrue and
Dart_IsFalse similar to the way we have Dart_IsNull?

[turnidge, 2011-11-04 00:03:17]

Please take another look.

Added two new files.

http://codereview.chromium.org/8446009/diff/1/runtime/include/dart_api.h
File runtime/include/dart_api.h (right):

http://codereview.chromium.org/8446009/diff/1/runtime/include/dart_api.h#newc...
runtime/include/dart_api.h:141: DART_EXPORT Dart_Handle
Dart_NewPersistentHandle(Dart_Handle object);
On 2011/11/03 21:45:25, asiva wrote:
> What is the use case for creating a new persistent handle from another
> persistent handle?
> Seems like clone functionality.

Someone who is passed a Dart_Handle doesn't know whether it is persistent or
not.  Even if they know it is persistent, they don't know what lifetime it will
have.  My thought is that it makes sense to be able to take an arbitrary
Dart_Handle and be able to save it for later.  Does this make sense?

http://codereview.chromium.org/8446009/diff/1/runtime/vm/dart_api_impl.cc
File runtime/vm/dart_api_impl.cc (right):

http://codereview.chromium.org/8446009/diff/1/runtime/vm/dart_api_impl.cc#new...
runtime/vm/dart_api_impl.cc:664: return value ? Api::True() : Api::False();
Okay.  Added code to protect against one of these handles getting deleted by
hijacking the "callback" field on the handle.

On 2011/11/03 21:45:25, asiva wrote:
> I think this is fine the only thing we may have to do is to protect ourselves
> from somebody calling Dart_DeletePersistentHandle(...) on these handles (null,
> true, false). 
> 
> Maybe delete is a nop when these handles are passed in.
> 
> On 2011/11/03 20:54:27, turnidge wrote:
> > How do you feel about this?  Does it violate expectation to be returning a
> > persistent handle here?  It is mostly transparent to the user.
>

http://codereview.chromium.org/8446009/diff/1/runtime/vm/dart_api_impl.cc#new...
runtime/vm/dart_api_impl.cc:669: bool* value) {
On 2011/11/03 21:45:25, asiva wrote:
> Instead of this function does it make sense to have a Dart_IsTrue and
> Dart_IsFalse similar to the way we have Dart_IsNull?

Discussed offline.  Let's defer adding these until we figure out what the
error-checking should be?

[siva, 2011-11-04 00:47:48]

LGTM