Diff for /gforth/except.fs between versions 1.4 and 1.25

version 1.4, 2002/09/24 17:57:28 version 1.25, 2010/12/31 18:09:02
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 \ catch, throw, etc.  \ catch, throw, etc.
   
 \ Copyright (C) 1999,2000 Free Software Foundation, Inc.  \ Copyright (C) 1999,2000,2003,2006,2007,2010 Free Software Foundation, Inc.
   
 \ This file is part of Gforth.  \ This file is part of Gforth.
   
 \ Gforth is free software; you can redistribute it and/or  \ Gforth is free software; you can redistribute it and/or
 \ modify it under the terms of the GNU General Public License  \ modify it under the terms of the GNU General Public License
 \ as published by the Free Software Foundation; either version 2  \ as published by the Free Software Foundation, either version 3
 \ of the License, or (at your option) any later version.  \ of the License, or (at your option) any later version.
   
 \ This program is distributed in the hope that it will be useful,  \ This program is distributed in the hope that it will be useful,
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 \ GNU General Public License for more details.  \ GNU General Public License for more details.
   
 \ You should have received a copy of the GNU General Public License  \ You should have received a copy of the GNU General Public License
 \ along with this program; if not, write to the Free Software  \ along with this program. If not, see http://www.gnu.org/licenses/.
 \ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.  
   
 \ !! use a separate exception stack?           anton  \ !! use a separate exception stack?           anton
   
 \ user-definable rollback actions  
   
 Defer 'catch  
 Defer 'throw  
   
 ' noop IS 'catch  
 ' noop IS 'throw  
   
 \ has? backtrace [IF]  \ has? backtrace [IF]
 Defer store-backtrace  Defer store-backtrace
 ' noop IS store-backtrace  ' noop IS store-backtrace
 \ [THEN]  \ [THEN]
   
 : (try) ( -- )  \ Ok, here's the story about how we get to the native code for the
     \ inline argument: address of the handler  \ recovery code in case of a THROW, and why there is all this funny
   \ stuff being compiled by TRY and RECOVER:
   
   \ Upon a THROW, we cannot just return through the ordinary return
   \ address, but have to use a different one, for code after the
   \ RECOVER.  How do we do that, in a way portable between the various
   \ threaded and native code engines?  In particular, how does the
   \ native code engine learn about the address of the native recovery
   \ code?
   
   \ On the Forth level, we can compile only references to threaded code.
   \ The only thing that translates a threaded code address to a native
   \ code address is docol, which is only called with EXECUTE and
   \ friends.  So we start the recovery code with a docol, and invoke it
   \ with PERFORM; the recovery code then rdrops the superfluously
   \ generated return address and continues with the proper recovery
   \ code.
   
   \ At compile time, since we cannot compile a forward reference (to the
   \ recovery code) as a literal (backpatching does not work for
   \ native-code literals), we produce a data cell (wrapped in AHEAD
   \ ... THEN) that we can backpatch, and compile the address of that as
   \ literal.
   
   \ Overall, this leads to the following resulting code:
   
   \   ahead
   \ +><recovery address>-+
   \ | then               |
   \ +-lit                |
   \   (try)              |
   \   ...                |
   \   (recover)          |
   \   ahead              |
   \   docol: <-----------+
   \   rdrop
   \   ...
   \   then
   \   ...
   
   \ !! explain handler on-stack structure
   
   Variable first-throw
   : nothrow ( -- ) \ gforth
       \G Use this (or the standard sequence @code{['] false catch drop})
       \G after a @code{catch} or @code{endtry} that does not rethrow;
       \G this ensures that the next @code{throw} will record a
       \G backtrace.
       first-throw on ;
   
   : (try0) ( -- aoldhandler )
       first-throw on
       handler @ ;
   
   [undefined] (try1) [if]
   : (try1) ( aoldhandler arecovery -- anewhandler )
       r>
       swap >r \ recovery address
       sp@ cell+ >r
       fp@ >r
       lp@ >r
       swap >r \ old handler
       rp@ swap \ new handler
       >r ;
   [endif]
   
   : (try2)
       handler ! ;
   
   : (try) ( ahandler -- )
       first-throw on
     r>      r>
     dup @ >r \ recovery address      swap >r \ recovery address
     rp@ 'catch >r  
     sp@ >r      sp@ >r
     fp@ >r      fp@ >r
     lp@ >r      lp@ >r
     handler @ >r      handler @ >r
     rp@ handler !      rp@ handler !
     backtrace-empty on      >r ;
     cell+ >r ;  
   
 : try ( compilation  -- orig ; run-time  -- ) \ gforth  \ : try ( compilation  -- orig ; run-time  -- R:sys1 ) \ gforth
     POSTPONE (try) >mark ; immediate compile-only  \     \G Start an exception-catching region.
   \     POSTPONE ahead here >r >mark 1 cs-roll POSTPONE then
   \     r> POSTPONE literal POSTPONE (try) ; immediate compile-only
   
   : try ( compilation  -- orig ; run-time  -- R:sys1 ) \ gforth
       \G Start an exception-catching region.
       POSTPONE ahead here >r >mark 1 cs-roll POSTPONE then
       POSTPONE (try0) r> POSTPONE literal POSTPONE (try1) POSTPONE (try2)
   ; immediate compile-only
   
 : (recover) ( -- )  
   : (endtry) ( -- )
     \ normal end of try block: restore handler, forget rest      \ normal end of try block: restore handler, forget rest
     r>      r>
     r> handler !      r> handler !
     rdrop \ lp      rdrop \ lp
     rdrop \ fp      rdrop \ fp
     rdrop \ sp      rdrop \ sp
     r> rp!  
     rdrop \ recovery address      rdrop \ recovery address
     >r ;      >r ;
   
 : recover ( compilation  orig1 -- orig2 ; run-time  -- ) \ gforth  : handler-intro, ( -- )
       docol: here 0 , 0 , code-address! \ start a colon def 
       postpone rdrop                    \ drop the return address
   ;
   
   : iferror ( compilation  orig1 -- orig2 ; run-time  -- ) \ gforth
       \G Starts the exception handling code (executed if there is an
       \G exception between @code{try} and @code{endtry}).  This part has
       \G to be finished with @code{then}.
     \ !! check using a special tag      \ !! check using a special tag
     POSTPONE (recover)      POSTPONE else handler-intro,
     POSTPONE else ; immediate compile-only  ; immediate compile-only
   
 : endtry ( compilation  orig -- ; run-time  -- ) \ gforth  : restore ( compilation  orig1 -- ; run-time  -- ) \ gforth
     POSTPONE then ; immediate compile-only      \G Starts restoring code, that is executed if there is an
       \G exception, and if there is no exception.
       POSTPONE iferror POSTPONE then
   ; immediate compile-only
   
   : endtry ( compilation  -- ; run-time  R:sys1 -- ) \ gforth
       \G End an exception-catching region.
       POSTPONE (endtry)
   ; immediate compile-only
   
   : endtry-iferror ( compilation  orig1 -- orig2 ; run-time  R:sys1 -- ) \ gforth
       \G End an exception-catching region while starting
       \G exception-handling code outside that region (executed if there
       \G is an exception between @code{try} and @code{endtry-iferror}).
       \G This part has to be finished with @code{then} (or
       \G @code{else}...@code{then}).
       POSTPONE (endtry) POSTPONE iferror POSTPONE (endtry)
   ; immediate compile-only
   
 :noname ( x1 .. xn xt -- y1 .. ym 0 / z1 .. zn error ) \ exception  :noname ( x1 .. xn xt -- y1 .. ym 0 / z1 .. zn error ) \ exception
     try      try
         execute 0          execute 0
     recover      iferror
         nip          nip
     endtry ;      then endtry ;
 is catch  is catch
   
   [undefined] (throw1) [if]
   : (throw1) ( ... ball frame -- ... ball )
       dup rp! ( ... ball frame )
       cell+ dup @ lp!
       cell+ dup @ fp!
       cell+ dup @ ( ... ball addr sp ) -rot 2>r sp! drop 2r>
       cell+ @ perform ;
   [endif]
       
 :noname ( y1 .. ym error/0 -- y1 .. ym / z1 .. zn error ) \ exception  :noname ( y1 .. ym error/0 -- y1 .. ym / z1 .. zn error ) \ exception
     ?DUP IF      ?DUP IF
         [ here forthstart 9 cells + ! ]          [ here forthstart 9 cells + ! ]
         store-backtrace          first-throw @ IF
               store-backtrace error-stack off
               first-throw off
           THEN
         handler @ ?dup-0=-IF          handler @ ?dup-0=-IF
             cr ." uncaught exception: " .error cr              >stderr cr ." uncaught exception: " .error cr
             2 (bye)              2 (bye)
             quit  \           quit
         THEN          THEN
         rp!          \ cr .s dup 64 dump
         r> handler !          (throw1)
         r> lp!  
         r> fp!  
         r> swap >r sp! drop r>  
         rdrop 'throw  
     THEN ;      THEN ;
 is throw  is throw
   

Removed from v.1.4  
changed lines
  Added in v.1.25


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