Re: What for Break Key No Work?

From	rickman <gnuarm@gmail.com>
Newsgroups	comp.lang.forth
Subject	Re: What for Break Key No Work?
Date	2014-07-27 16:35 -0400
Organization	A noiseless patient Spider
Message-ID	<lr3nrk$bcb$1@dont-email.me> (permalink)
References	(7 earlier) <854d2f08-ef40-4535-a008-1d2f568da058@googlegroups.com> <lqunkd$ufd$1@dont-email.me> <2c176e57-2f20-47df-8293-c2b7860365dd@googlegroups.com> <lqv284$kae$1@dont-email.me> <2014Jul27.150857@mips.complang.tuwien.ac.at>

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On 7/27/2014 9:08 AM, Anton Ertl wrote:
> rickman <gnuarm@gmail.com> writes:
>> What I want to know is how the process conveys
>> control back to the Forth outer interpreter.  The Forth process is stuck
>> in a loop and the CPU is now executing the OS.  How does the Forth
>> process return to running the interpreter rather than the user code?
>
> In Gforth, it works like this: the signal handler performs a longjmp()
> to a place that IIRC is in the C function that calls the actual engine
> function.  This C function then pushes the throw code on the stack,
> and sets the IP to the start of THROW, and then invokes the engine,
> which dutyfully performs a THROW.

I don't know what you mean by the "engine function".  Is that the inner 
interpreter or do you mean the THROW function?  I guess I think in terms 
of STC but you are talking DTC or ITC?

> This is all done with a separate data and return stack area, and the
> THROW then sets the stack pointers from the ones stored when the
> surrounding CATCH was called.  Unless the application has its own
> CATCH, the surrounding CATCH is from the system; after this CATCH has
> caught the THROW, it produces an error message and restarts the text
> interpreter.

So the signal handler has to set it's own stack pointer on entry to a 
dedicated memory space, no?

> In any case, the interrupted definition never regains control.
>
> Does that answer your question?

Almost.  What was actually confusing me is that I don't think I've ever 
learned the details of how control passes from the OS running in kernel 
mode (or whatever it is called) to the application running in protected 
mode.  I kept getting mixed up thinking control could only pass to the 
application at the point it left off.  I expect that the OS simply 
restores all context of the application except for setting the address 
of the signal handler for the program counter.  BTW, is there a 
preferred name for the program counter vs. instruction pointer?  I use 
them interchangeably.  I am referring to the CPU's IP, not the Forth IP.

> As a twist, the debugging engine (gforth, not gforth-fast) saves IP
> and RP frequently in a global variable; this allows the C part to push
> IP (which points to the interrupted word at this time) on the return
> stack before invoking THROW; and THROW then produces a full backtrace,
> instead of a backtrace that only starts with (essentially) the next
> surrounding CATCH.

-- 

Rick

Thread

What for Break Key No Work? Jason Damisch <jasondamisch@yahoo.com> - 2014-07-22 14:44 -0700
  Re: What for Break Key No Work? Roger Levy <roger.levy@gmail.com> - 2014-07-22 14:50 -0700
    Re: What for Break Key No Work? Jason Damisch <jasondamisch@yahoo.com> - 2014-07-22 15:04 -0700
      Re: What for Break Key No Work? Jason Damisch <jasondamisch@yahoo.com> - 2014-07-22 16:03 -0700
      Re: What for Break Key No Work? BruceMcF <agila61@netscape.net> - 2014-07-22 18:34 -0700
        Re: What for Break Key No Work? Jason Damisch <jasondamisch@yahoo.com> - 2014-07-22 19:32 -0700
          Re: What for Break Key No Work? Spam@ControlQ.com - 2014-07-22 22:43 -0400
            Re: What for Break Key No Work? Jason Damisch <jasondamisch@yahoo.com> - 2014-07-23 09:57 -0700
              Re: What for Break Key No Work? "Elizabeth D. Rather" <erather@forth.com> - 2014-07-23 07:12 -1000
                Re: What for Break Key No Work? Jason Damisch <jasondamisch@yahoo.com> - 2014-07-23 10:15 -0700
          Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-22 22:44 -0400
            Re: What for Break Key No Work? Jason Damisch <jasondamisch@yahoo.com> - 2014-07-23 09:58 -0700
              Re: What for Break Key No Work? "Elizabeth D. Rather" <erather@forth.com> - 2014-07-23 21:28 -1000
          Re: What for Break Key No Work? BruceMcF <agila61@netscape.net> - 2014-07-23 13:12 -0700
            Re: What for Break Key No Work? Jason Damisch <jasondamisch@yahoo.com> - 2014-07-23 14:52 -0700
              Re: What for Break Key No Work? Mark Wills <markwills1970@gmail.com> - 2014-07-24 01:54 -0700
                Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-24 07:54 -0400
                Re: What for Break Key No Work? Mark Wills <markwills1970@gmail.com> - 2014-07-24 06:49 -0700
                Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-24 10:39 -0400
                Re: What for Break Key No Work? bruce.mcfarling@gmail.com - 2014-07-24 08:52 -0700
                Re: What for Break Key No Work? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-07-24 13:07 -0500
                Re: What for Break Key No Work? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-07-25 10:50 +0000
                Re: What for Break Key No Work? Bernd Paysan <bernd.paysan@gmx.de> - 2014-07-25 14:38 +0200
                Re: What for Break Key No Work? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-07-25 17:07 +0000
                Re: What for Break Key No Work? Bernd Paysan <bernd.paysan@gmx.de> - 2014-07-26 00:36 +0200
                Re: What for Break Key No Work? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-07-27 13:47 +0000
                Re: What for Break Key No Work? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-07-25 09:21 -0500
                Re: What for Break Key No Work? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-07-25 17:10 +0000
                Re: What for Break Key No Work? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-07-26 04:38 -0500
                Re: What for Break Key No Work? Bernd Paysan <bernd.paysan@gmx.de> - 2014-07-26 15:56 +0200
                Re: What for Break Key No Work? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-07-27 13:27 +0000
                Re: What for Break Key No Work? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-07-27 09:36 -0500
                Re: What for Break Key No Work? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-07-28 11:38 +0000
                Re: What for Break Key No Work? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-07-28 10:42 -0500
                Re: What for Break Key No Work? "Rod Pemberton" <dont_use_email@xnothavet.cqm> - 2014-07-25 16:56 -0400
                Re: What for Break Key No Work? "Elizabeth D. Rather" <erather@forth.com> - 2014-07-26 09:33 +0000
                Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-24 19:40 -0400
                Re: What for Break Key No Work? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-07-25 00:00 +0000
                Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-24 22:17 -0400
                Re: What for Break Key No Work? bruce.mcfarling@gmail.com - 2014-07-25 06:54 -0700
                Re: What for Break Key No Work? "Elizabeth D. Rather" <erather@forth.com> - 2014-07-25 13:13 -0400
                Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-25 13:24 -0400
                Re: What for Break Key No Work? bruce.mcfarling@gmail.com - 2014-07-25 14:37 -0700
                Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-25 19:01 -0400
                Re: What for Break Key No Work? bruce.mcfarling@gmail.com - 2014-07-25 16:20 -0700
                Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-25 22:02 -0400
                Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-25 22:17 -0400
                Re: What for Break Key No Work? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-07-26 09:09 +0000
                Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-26 05:36 -0400
                Re: What for Break Key No Work? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-07-26 04:41 -0500
                Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-26 22:50 -0400
                Re: What for Break Key No Work? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-07-27 02:49 -0500
                Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-27 15:08 -0400
                Re: What for Break Key No Work? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-07-27 14:11 -0500
                Re: What for Break Key No Work? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-07-28 12:00 +0000
                Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-28 10:41 -0400
                Re: What for Break Key No Work? Bernd Paysan <bernd.paysan@gmx.de> - 2014-07-27 14:31 +0200
                Re: What for Break Key No Work? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-07-27 13:08 +0000
                Re: What for Break Key No Work? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-07-27 19:37 +0000
                Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-27 16:35 -0400
                Re: What for Break Key No Work? "Elizabeth D. Rather" <erather@forth.com> - 2014-07-27 22:24 +0000
                Re: What for Break Key No Work? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-07-28 13:14 +0000
                Re: What for Break Key No Work? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-07-28 03:41 -0500
                Re: What for Break Key No Work? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-07-28 12:09 +0000
                Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-28 10:48 -0400
                Re: What for Break Key No Work? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-07-28 15:29 +0000
                Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-28 14:30 -0400
                Re: What for Break Key No Work? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-07-29 08:12 +0000
                Re: What for Break Key No Work? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-07-28 13:10 +0000
                Re: What for Break Key No Work? bruce.mcfarling@gmail.com - 2014-07-27 11:33 -0700
                Re: What for Break Key No Work? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-07-28 11:55 +0000
                Re: What for Break Key No Work? "Alex McDonald" <blog@rivadpm.com> - 2014-07-28 14:03 +0100
                Re: What for Break Key No Work? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-07-27 13:02 +0000
                Re: What for Break Key No Work? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-07-26 08:57 +0000
                Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-26 05:05 -0400
                Re: What for Break Key No Work? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-07-26 09:20 +0000
            Re: What for Break Key No Work? "Alex McDonald" <blog@rivadpm.com> - 2014-07-23 23:48 +0100
            Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-24 04:53 -0400
              Re: What for Break Key No Work? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-07-24 10:59 +0000
                Re: What for Break Key No Work? mhx@iae.nl - 2014-07-24 04:23 -0700
          Re: What for Break Key No Work? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-07-24 19:28 +0000
            Re: What for Break Key No Work? "Elizabeth D. Rather" <erather@forth.com> - 2014-07-24 13:01 -1000
              Re: What for Break Key No Work? Roelf Toxopeus <rt4all@notthis.hetnet.nl> - 2014-07-25 10:13 +0200
      Re: What for Break Key No Work? "Elizabeth D. Rather" <erather@forth.com> - 2014-07-22 17:11 -1000
        Re: What for Break Key No Work? Jason Damisch <jasondamisch@yahoo.com> - 2014-07-23 09:59 -0700
  Re: What for Break Key No Work? David Schultz <abuse@127.0.0.1> - 2014-07-22 17:47 -0500
    Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-22 19:12 -0400
      Re: What for Break Key No Work? Jason Damisch <jasondamisch@yahoo.com> - 2014-07-22 16:21 -0700
        Re: What for Break Key No Work? rickman <gnuarm@gmail.com> - 2014-07-22 22:51 -0400
  Re: What for Break Key No Work? Matthias Trute <matthias.trute@gmail.com> - 2014-07-23 02:18 -0700
  Re: What for Break Key No Work? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-07-23 13:21 +0000
    Re: What for Break Key No Work? Jason Damisch <jasondamisch@yahoo.com> - 2014-07-23 10:02 -0700
    Re: What for Break Key No Work? Bernd Paysan <bernd.paysan@gmx.de> - 2014-07-24 04:10 +0200
  Re: What for Break Key No Work? mhx@iae.nl - 2014-07-23 13:45 -0700
  Re: What for Break Key No Work? BruceMcF <agila61@netscape.net> - 2014-07-23 16:37 -0700
  Re: What for Break Key No Work? "Clyde W. Phillips Jr." <cwpjr02@gmail.com> - 2014-07-30 16:13 -0700
  Re: What for Break Key No Work? francois.ganza@wanadoo.fr - 2014-07-30 22:55 -0700

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