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RE: broken CTRL-BREAK handling

A good suggestion.

Under Linux or Solaris, the standard way of forcing Sun's JVM to dump the
current thread stacks is

$ kill -SIGQUIT <pid-of-your-jvm>

or equivalently:

$ kill -3 <pid-of-your-jvm>

On AIX, with IBM's JVM you can use -SIGUSR1.
Not sure of other JVM ports, but that's how the two JVMs
I've used do it.

Unfortunately, the win32 version of Sun's JVM is a
native Win32 app, and doesn't handle signals in *nix fashion...
since it's only got the Win32 API at its disposal.  All the
signal handling that cygwin uses/provides is implemented as part of
cygwin in other words.
Sun's JVM registers a console ctrl handler, which when invoked
with type==CTRL_BREAK_EVENT dumps the thread stacks.  The
interaction with cygwin is that when I start JVM from cygwin's
bash, a CTRL-BREAK results in a kill of all of the processes in
the process group (including my JVM process) before the JVM's
control handler gets called.  Thus the root of my particular
problem, which I was trying to work around.

I [re]discovered that can press the close button ([X]) at the
upper right corner of the bash console window to produce the
stack trace.  Not as pretty, and doesn't work in Emacs (C-c C-\),
but it's a work around nonetheless.

Now, if I could get Sun to port their JVM over to cygwin,
and then setup a proper POSIX-style signal handler
such as cygwin provides (which win32 doesn't)... but
then I wake up and realize I'm daydreaming again.

Thanks for the suggestion.  It was definitely worth a shot.


-----Original Message-----
From: Heribert Dahms []
Sent: Wednesday, July 18, 2001 2:42 PM
To: 'Troy Noble'; ''
Subject: RE: broken CTRL-BREAK handling

Hi Troy,

for the unix-emulation-centered like me it's a non issue
and I'd turn the question into:
Is there a (standard) way of generating a JVM dump under Unix?
If so, you may try that under Cygwin.

Bye, Heribert (

> -----Original Message-----
> From:	Troy Noble []
> Sent:	Wednesday, July 18, 2001 18:33
> To:	''
> Subject:	RE: broken CTRL-BREAK handling
	[Heribert]  [snip]

> I want to go on record as saying that I'm still not convinced it's
> entirely right for the ctrl handler to swallow the CTRL-BREAK and
> turn it into a SIGINT in all cases.  Let me explain.  If I press
> CTRL-BREAK in a cmd window JVM dumps stack traces, if I do the same
> in bash/cygwin console window it doesn't.
> Bottom line... that still feels broken to me if the intent is for
> cygwin (more specifically, the bash shell running with cygwin) to
> be able to launch/stop native win32 apps with the same semantics one
> has come to expect when running cmd shell.
> If that's not the goal, then it's a non-issue.
	[Heribert]  [snip]

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