Add flow graph printing into a .cfg file with flag --print-flow-graph-file.

vm/dart.h

Index: vm/dart.h
===================================================================
--- vm/dart.h	(revision 8145)
+++ vm/dart.h	(working copy)
@@ -33,10 +33,17 @@
   }
   static DebugInfo* pprof_symbol_generator() { return pprof_symbol_generator_; }
 
+  static void set_flow_graph_writer(FileWriterFunction writer_function) {
+    flow_graph_writer_ = writer_function;
+  }
+
+  static FileWriterFunction flow_graph_writer() { return flow_graph_writer_; }
+
  private:
   static Isolate* vm_isolate_;
   static ThreadPool* thread_pool_;
   static DebugInfo* pprof_symbol_generator_;
+  static FileWriterFunction flow_graph_writer_;

[siva, 2012/06/04 18:23:57]

If you have this as a static function with a static file handle, how does it
work in multiple isolate situations? Is it ok if you get multiple flow graphs
from different isolates intertwined in the same output file?

[Florian Schneider, 2012/06/06 11:06:10]

It does not work.  I'm fine for now with it working only for the single-isolate
case: The tests and benchmarks we're looking at do not create multiple isolate.

Alternative would be to either have one file per isolate or control file access
using a lock so that only one isolate at a time can write a flow graph.

[siva, 2012/06/06 17:02:47]

Having one file per isolate is probably the way to go.
I think in your current case you might think it is fine if it works only for a
single isolate but somebody else might come in try this flag on a test which has
multiple isolates and without realizing that the implementation of this flag is
broken might spend hours trying to debug why the visualizer is not displaying
stuff correctly.

If you intend to leave it as is, at least put a warning when this option is used
which states "this option is only partially implemented and does not work at all
when the application uses multiple isolates". 

On 2012/06/06 11:06:10, Florian Schneider wrote:

[Florian Schneider, 2012/06/07 09:32:26]

I can add a TODO. I don't think this is a typical use case. If there is a large
number of isolates though it may be very confusing to have one file per isolate.
- i.e. finding the method of interest would involve grepping the files first.

 };
 
 }  // namespace dart