Implement "wait for connection" feature

Implement "wait for connection" feature

[Peter Rybin, 2009-12-10 21:31:14]

Hi Soren

I'm putting "wait for connection" feature separately into this CL.

> I am not sure what happens here when the wait for debugger connection flag is
> set.
I think this should disable "autocontinue" behavior of V8 when there is not
message handler. So that once V8 paused, it simply stays paused.

> Isn't V8 execution supposed to wait until a debugger comes along and
> processes the first debugger message?

Probably we should support both options: V8 is waiting for debugger connection
and V8 starts without connection.
Currently we support only second scenario.

> Should the debug break flag be raised to
> ensure that a break will happen as soon as any code is executed?
I didn't think about this. I though about manually putting "debugger;" statement
in the beginning of program.
Probably I should try to with this runtime flag.

> You will need to provide some test which uses and tests this new flag. There
are
> some tests covering the DebugAgent, but they probably needs to be extended.

I'm working on this.

[Peter Rybin, 2009-12-10 22:04:48]

> > Should the debug break flag be raised to
> > ensure that a break will happen as soon as any code is executed?
> I didn't think about this. I though about manually putting "debugger;"
statement
> in the beginning of program.
> Probably I should try to with this runtime flag.

Can I do this just by calling v8::Debug::DebugBreak() from
v8::Debug::EnableAgent() like in a patch?

[Søren Thygesen Gjesse, 2009-12-11 09:45:52]

LGTM

http://codereview.chromium.org/489005/diff/3001/4003
File src/debug.cc (right):

http://codereview.chromium.org/489005/diff/3001/4003#newcode2487
src/debug.cc:2487: // Simply ignore message.
Maybe this should be extended to keep all messages (or block on the first) for
the debugger when it connects in a future changelist.

http://codereview.chromium.org/489005/diff/3001/4003#newcode2493
src/debug.cc:2493: if (wait_for_connection) {
You should rephrase this comment to say that a break is actually set.

[Peter Rybin, 2009-12-11 11:30:13]

http://codereview.chromium.org/489005/diff/3001/4003
File src/debug.cc (right):

http://codereview.chromium.org/489005/diff/3001/4003#newcode2487
src/debug.cc:2487: // Simply ignore message.
On 2009/12/11 09:45:52, Søren Gjesse wrote:
> Maybe this should be extended to keep all messages (or block on the first) for
> the debugger when it connects in a future changelist.

Fair enough.
On the other hand I don't see a use case for this now. Remote debugger should be
able to attach just in any moment without needing update on all previous
messages.

http://codereview.chromium.org/489005/diff/3001/4003#newcode2493
src/debug.cc:2493: if (wait_for_connection) {
On 2009/12/11 09:45:52, Søren Gjesse wrote:
> You should rephrase this comment to say that a break is actually set.

Done.