Debugger support to display global variables

Debugger support to display global variables

- Add library id to ActivationFrame
- Add debugger function to get all global variables visible in
  a library (including imported variables).
- Add LibraryPrefixIterator
- Fix Dart_GetLibraryImports
Committed: https://code.google.com/p/dart/source/detail?r=9121

[hausner, 2012-06-26 16:42:40]

FYI Pavel: look for the added parameter in Dart_ActivationFrameInfo.

Thank you.

[hausner, 2012-06-26 16:57:06]

Thanks Srdjan.

[srdjan, 2012-06-26 17:08:26]

LGTM

http://codereview.chromium.org/10657048/diff/6001/runtime/vm/debugger.cc
File runtime/vm/debugger.cc (right):

http://codereview.chromium.org/10657048/diff/6001/runtime/vm/debugger.cc#newc...
runtime/vm/debugger.cc:1115: Object& entry = Object::Handle(isolate_);
Why all this isolates_ passing? Is there a performance problem here?

http://codereview.chromium.org/10657048/diff/6001/runtime/vm/debugger.cc#newc...
runtime/vm/debugger.cc:1148:
GrowableObjectArray::Handle(GrowableObjectArray::New(8));
Why 8? Maybe better to not pass the length if you do not know it.

[hausner, 2012-06-26 17:32:12]

Thank you for the review.

http://codereview.chromium.org/10657048/diff/6001/runtime/vm/debugger.cc
File runtime/vm/debugger.cc (right):

http://codereview.chromium.org/10657048/diff/6001/runtime/vm/debugger.cc#newc...
runtime/vm/debugger.cc:1115: Object& entry = Object::Handle(isolate_);
On 2012/06/26 17:08:26, srdjan wrote:
> Why all this isolates_ passing? Is there a performance problem here?

As discussed offline, it has a tiny impact on performance. Each parameterless
call to Handle() results in a call to get the current thread, which is not
entirely free. We all agree that this only makes sense when a pointer to the
isolate happens to be easily accessible.

http://codereview.chromium.org/10657048/diff/6001/runtime/vm/debugger.cc#newc...
runtime/vm/debugger.cc:1148:
GrowableObjectArray::Handle(GrowableObjectArray::New(8));
On 2012/06/26 17:08:26, srdjan wrote:
> Why 8? Maybe better to not pass the length if you do not know it. 

No particular reason. It just eliminates the first two or so reallocate and copy
steps. If I don't pass an initial size, then GrowableObjectArray will, and it
doesn't know any better either... :)

[siva, 2012-06-26 18:46:28]

lgtm

http://codereview.chromium.org/10657048/diff/6001/runtime/vm/object.cc
File runtime/vm/object.cc (right):

http://codereview.chromium.org/10657048/diff/6001/runtime/vm/object.cc#newcod...
runtime/vm/object.cc:4697: MoveToNext();
Your suggestion of 'Advance' in another context seems like a good name instead
of MoveToNext. This is just a suggestion please feel free to ignore.

http://codereview.chromium.org/10657048/diff/6001/tools/ddbg.dart
File tools/ddbg.dart (right):

http://codereview.chromium.org/10657048/diff/6001/tools/ddbg.dart#newcode42
tools/ddbg.dart:42: pg <id> Print global variables visible given library
This line doesn't seem to read well.

Did you mean 'Print global variables visible for given library id'

[hausner, 2012-06-26 19:35:07]

Thanks Siva. I'll make the changes in a separate checkin.