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	2014-07-28 10:48 -0400
Organization	A noiseless patient Spider
Message-ID	<lr5ns2$igh$1@dont-email.me> (permalink)
References	(8 earlier) <2c176e57-2f20-47df-8293-c2b7860365dd@googlegroups.com> <lqv284$kae$1@dont-email.me> <2014Jul27.150857@mips.complang.tuwien.ac.at> <lr3nrk$bcb$1@dont-email.me> <2014Jul28.140927@mips.complang.tuwien.ac.at>

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On 7/28/2014 8:09 AM, Anton Ertl wrote:
> rickman <gnuarm@gmail.com> writes:
>> 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
>
> Yes, plus more: The engine() function contains all the primitives of
> the Forth system.  When you invoke it with a given IP, it starts
> executing the Forth code at this IP and continues executing Forth code
> until it happens upon (BYE) or until a signal handler is invoked.
>
>>> 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?
>
> For the data and return stacks, it uses dedicated memory space,
> because it does not know where the data and return stack pointers of
> the engine point to, anyway.  Later, THROW sets these stack pointers
> to the values they had when the innermost CATCH was called.

Why would the signal handler not know this?  It should be running in the 
same context.  The data and return stacks are just register values which 
should be the same as in the user code, no?  If not, what values do the 
registers have, arbitrary?


> For the C stack, in most cases it is sufficient to use the existing C
> stack in the signal handler, but, as explained in another posting, we
> have had cases where the C stack pointer was corrupted before the
> exception, and to cater for such cases we also use a separate stack
> area for the C stack.
>
>> 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.
>
> Yes, something like that.
>
>>   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.
>
> Following fig-Forth, I call the Forth interpreter's thing IP.
> Following 6502 usage, I call the CPU's thing PC.
>
> Unfortunately, Intel chooses to call the PC IP.

I think I am on track enough to understand what is happening.  Thanks.

-- 

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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