version 1.1, 2000/07/24 13:48:36
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version 1.11, 2006/10/08 11:30:56
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\ catch, throw, etc. |
\ catch, throw, etc. |
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\ Copyright (C) 1999 Free Software Foundation, Inc. |
\ Copyright (C) 1999,2000,2003 Free Software Foundation, Inc. |
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\ This file is part of Gforth. |
\ This file is part of Gforth. |
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Line 16
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\ 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, write to the Free Software |
\ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. |
\ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA. |
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\ !! use a separate exception stack? anton |
\ !! use a separate exception stack? anton |
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Line 33 Defer store-backtrace
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Line 33 Defer store-backtrace
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' noop IS store-backtrace |
' noop IS store-backtrace |
\ [THEN] |
\ [THEN] |
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: (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 |
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\ stuff being compiled by TRY and RECOVER: |
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\ Upon a THROW, we cannot just return through the ordinary return |
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\ address, but have to use a different one, for code after the |
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\ RECOVER. How do we do that, in a way portable between the various |
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\ threaded and native code engines? In particular, how does the |
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\ native code engine learn about the address of the native recovery |
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\ code? |
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\ On the Forth level, we can compile only references to threaded code. |
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\ The only thing that translates a threaded code address to a native |
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\ code address is docol, which is only called with EXECUTE and |
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\ friends. So we start the recovery code with a docol, and invoke it |
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\ with PERFORM; the recovery code then rdrops the superfluously |
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\ generated return address and continues with the proper recovery |
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\ code. |
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\ At compile time, since we cannot compile a forward reference (to the |
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\ recovery code) as a literal (backpatching does not work for |
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\ native-code literals), we produce a data cell (wrapped in AHEAD |
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\ ... THEN) that we can backpatch, and compile the address of that as |
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\ literal. |
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\ Overall, this leads to the following resulting code: |
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\ ahead |
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\ +><recovery address>-+ |
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\ | then | |
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\ +-lit | |
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\ (try) | |
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\ ... | |
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\ (recover) | |
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\ ahead | |
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\ docol: <-----------+ |
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\ rdrop |
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\ ... |
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\ then |
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\ ... |
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\ !! explain handler on-stack structure |
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: (try) ( ahandler -- ) |
r> |
r> |
dup dup @ + >r \ recovery address |
swap >r \ recovery address |
rp@ 'catch >r |
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 ; |
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: try ( compilation -- orig ; run-time -- ) \ gforth |
: try ( compilation -- orig ; run-time -- ) \ gforth |
POSTPONE (try) >mark ; immediate compile-only |
\ !! does not work correctly for gforth-native |
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POSTPONE ahead here >r >mark 1 cs-roll POSTPONE then |
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r> POSTPONE literal POSTPONE (try) ; immediate compile-only |
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: (recover) ( -- ) |
: (recover) ( -- ) |
\ normal end of try block: restore handler, forget rest |
\ normal end of try block: restore handler, forget rest |
Line 63 Defer store-backtrace
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Line 106 Defer store-backtrace
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: recover ( compilation orig1 -- orig2 ; run-time -- ) \ gforth |
: recover ( compilation orig1 -- orig2 ; run-time -- ) \ gforth |
\ !! check using a special tag |
\ !! check using a special tag |
POSTPONE (recover) |
POSTPONE (recover) |
POSTPONE else ; immediate compile-only |
POSTPONE else |
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docol: here 0 , 0 , code-address! \ start a colon def |
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postpone rdrop \ drop the return address |
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; immediate compile-only |
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: endtry ( compilation orig -- ; run-time -- ) \ gforth |
: endtry ( compilation orig -- ; run-time -- ) \ gforth |
POSTPONE then ; immediate compile-only |
POSTPONE then ; immediate compile-only |
Line 79 is catch
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Line 125 is catch
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: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 |
store-backtrace error-stack off |
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! |
rp! |
r> handler ! |
r> handler ! |
r> lp! |
r> lp! |
r> fp! |
r> fp! |
r> swap >r sp! drop r> |
r> swap >r sp! drop r> |
rdrop 'throw |
rdrop 'throw r> perform |
THEN ; |
THEN ; |
is throw |
is throw |
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[IFDEF] rethrow |
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:noname ( y1 .. ym error/0 -- y1 .. ym / z1 .. zn error ) \ exception |
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?DUP IF |
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handler @ ?dup-0=-IF |
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>stderr cr ." uncaught exception: " .error cr |
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2 (bye) |
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\ quit |
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THEN |
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rp! |
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r> handler ! |
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r> lp! |
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r> fp! |
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r> swap >r sp! drop r> |
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rdrop 'throw r> perform |
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THEN ; |
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is rethrow |
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[THEN] |
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