--- gforth/except.fs	2006/10/08 11:30:56	1.11
+++ gforth/except.fs	2007/12/31 17:34:58	1.20
@@ -1,6 +1,6 @@
 \ catch, throw, etc.
 
-\ Copyright (C) 1999,2000,2003 Free Software Foundation, Inc.
+\ Copyright (C) 1999,2000,2003,2006,2007 Free Software Foundation, Inc.
 
 \ This file is part of Gforth.
 
@@ -20,14 +20,6 @@
 
 \ !! use a separate exception stack?           anton
 
-\ user-definable rollback actions
-
-Defer 'catch
-Defer 'throw
-
-' noop IS 'catch
-' noop IS 'throw
-
 \ has? backtrace [IF]
 Defer store-backtrace
 ' noop IS store-backtrace
@@ -76,10 +68,18 @@ Defer store-backtrace
 
 \ !! 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 ;
+
 : (try) ( ahandler -- )
+    first-throw on
     r>
     swap >r \ recovery address
-    rp@ 'catch >r
     sp@ >r
     fp@ >r
     lp@ >r
@@ -87,72 +87,78 @@ Defer store-backtrace
     rp@ handler !
     >r ;
 
-: try ( compilation  -- orig ; run-time  -- ) \ gforth
-    \ !! does not work correctly for gforth-native
+: try ( compilation  -- orig ; run-time  -- R:sys1 ) \ gforth
+    \G Start an exception-catching region.
     POSTPONE ahead here >r >mark 1 cs-roll POSTPONE then
     r> POSTPONE literal POSTPONE (try) ; immediate compile-only
 
-: (recover) ( -- )
+: (endtry) ( -- )
     \ normal end of try block: restore handler, forget rest
     r>
     r> handler !
     rdrop \ lp
     rdrop \ fp
     rdrop \ sp
-    r> rp!
     rdrop \ recovery address
     >r ;
 
-: recover ( compilation  orig1 -- orig2 ; run-time  -- ) \ gforth
-    \ !! check using a special tag
-    POSTPONE (recover)
-    POSTPONE else
+: 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
+    POSTPONE else handler-intro,
 ; immediate compile-only
 
-: endtry ( compilation  orig -- ; run-time  -- ) \ gforth
-    POSTPONE then ; immediate compile-only
+: restore ( compilation  orig1 -- ; run-time  -- ) \ gforth
+    \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
     try
 	execute 0
-    recover
-        nip
-    endtry ;
+    iferror
+	nip
+    then endtry ;
 is catch
 
 :noname ( y1 .. ym error/0 -- y1 .. ym / z1 .. zn error ) \ exception
     ?DUP IF
 	[ here forthstart 9 cells + ! ]
-	store-backtrace error-stack off
-	handler @ ?dup-0=-IF
-	    >stderr cr ." uncaught exception: " .error cr
-	    2 (bye)
-\	    quit
+	first-throw @ IF
+	    store-backtrace error-stack off
+	    first-throw off
 	THEN
-	rp!
-	r> handler !
-	r> lp!
-	r> fp!
-	r> swap >r sp! drop r>
-	rdrop 'throw r> perform
-    THEN ;
-is throw
-[IFDEF] rethrow
-:noname ( y1 .. ym error/0 -- y1 .. ym / z1 .. zn error ) \ exception
-    ?DUP IF
 	handler @ ?dup-0=-IF
 	    >stderr cr ." uncaught exception: " .error cr
 	    2 (bye)
 \	    quit
 	THEN
-	rp!
-	r> handler !
-	r> lp!
-	r> fp!
-	r> swap >r sp! drop r>
-	rdrop 'throw r> perform
+        dup rp! ( ... ball frame )
+        cell+ dup @ lp!
+        cell+ dup @ fp!
+        cell+ dup @ ( ... ball addr sp ) -rot 2>r sp! drop 2r>
+        cell+ @ perform
     THEN ;
-is rethrow
-[THEN]
\ No newline at end of file
+is throw