Ok, I think I understand…
So if the hardware was say an IBM 370, the
code would be something like:
ENTRY MAIN
MAIN DS 0A
DC A(SETUP)
DC A(PERFORMA)
DC A(PERFORMB)
END
PERFORMA DS 0A
DC A(CALL)
DC A(MYRTN)
DC A(P1)
DC A(P2)
DC A(NULL)
. . .
Plus much much more detail.
Then your “inner interpreter” would basically
trip thru the code calling routines and passing parameters as required for
things like MOVE, COMPUTE, CALL, READ/WRITE etc…
Do I have it right?
From: Jeff Chimene [mailto:address@hidden
Sent: May 25, 2009 2:47 PM
To: Ron
Norman
Subject: Re: [open-cobol-list]
Proposed addition to OpenCOBOL: an object module generator
HI Ron:
For future, I'd prefer to keep this discussion on the list.
Other comments in line.
On 05/25/2009 11:32 AM, Ron Norman
wrote:
The module format COFF vs ELF is a minor issue compared to which machine
instruction set would be used.
Agreed. That's why I omitted it from the proposal.
In the proposed model, the executable code is all C.
As for the proposed object file, when decoded to assembler, it might look
something like:
.entry MAIN
.extern SETUP
.extern PERFORMA
.extern PERFORMB
.end
The concept is that a C routine (aka the "inner interpreter") calls
the routines (also written in C, in the current cob1 library and a TBD
library). There needs to be additional code that replaces the current C code
emitted by the COBOL compiler, The new C code will handle branching and data
structures (data definition, working storage). That new code would be in the
TBD library.
To reiterate, all code that must be portable is written in GNU C. The object
file output by the COBOL compiler contains no executable code, only pointers to
routines in cob1 and another TBD library. The organization of these pointers
is commonly referred to as a "thread".
Cheers,
jec
-----Original Message-----
From: Jeff Chimene [mailto:address@hidden]
Sent: May 25, 2009 11:16 AM
To: Ron Norman
Subject: Re: [open-cobol-list] Proposed addition to OpenCOBOL: an
objectmodule generator
On Mon, May 25, 2009 at 6:15 AM, Ron Norman <address@hidden> wrote:
Just my 2 cents, but GNU C does generate object modules on the
platform in
use.
Agreed. One of the proposal's goals is to generate object files that
represent compiled COBOL code as opposed to compiled C code.
If OpenCOBOL generated the object module directly then it needs to
deal with
the many different hardware platforms, Intel x86, Itanium, PA-Risc,
PowerPC,
SPARC, etc...
The object module format would be COFF. That /should/ be portable
across those systems.
GNU C does have some internal features which seem to allow GOTO and
computed
GOTO to be implemented.
Agreed. However, I don't suggest transforming the current C code into
threaded C code. I am suggesting using the theaded model in object
files. The run-time system uses the GNU C syntax for indirect jumps to
follow the thread.
Roger While would know better than I.
I waiting for feedback from him on this proposal.