\ CRASH-PROOFING TEST RESULTS (1997-08-21, updated 2007-04-27)

\ Find a value not likely to be an execution token.
1 ALIGNED CONSTANT NotAnXT
\ Find an address likely to be outside the data space.
-4 ALIGNED CONSTANT NotADataAddress
\ Find an address which is likely to be unaligned.
HERE ALIGNED 1+ CONSTANT NotAligned
\ Create a : word which cannot be a macro.
: _DROP DROP ;

: BadExecute ( -- ) NotAnXT EXECUTE ;
: BadAddress ( -- ) NotADataAddress @ DROP ;
: BadAlign ( -- ) NotAligned @ DROP ;
: BadReturn ( -- ) NotAnXT >R ;
: BadCode ( -- ) ['] _DROP 20 0 FILL 0 ['] _DROP EXECUTE ; \ Try executing it
: BadRes1 ( -- n1 n2 ) 9 0 /MOD ; \ Divide by zero
: BadRes2 ( -- ) 0 1 1 UM/MOD ; \ Out of range
: BadBreak ( -- u1 u2 ) BEGIN AGAIN ; \ Try to interrupt loop
: BadNumb ( -- ) 1 1 BASE ! . ; \ Loops forever?

Result Codes 0 harmless, no need to detect action.
-2 prevents action, reports cause and location, continues at Forth prompt.
-3 prevents action, reports cause only, continues at Forth prompt.
-4 prevents action, reports "Error found", continues at Forth prompt.
-6 executes action, but values returned are incorrect.
-7 prevents action, reports cause only, empties dictionary, continues at Forth prompt.
-10 prevents action, reports cause and location, exits Forth.
-11 prevents action, reports cause only, exits Forth.
-12 prevents action, reports "Error found", exits Forth.
-14 no message, exits Forth.
-16 no message, hangs Forth but computer need not be re-booted.
-18 no message, hangs Forth and computer must be re-booted.
-20 no message, corrupts Forth which hangs at some later time.


Compiler Bad Execute Bad Address Bad Align Bad Return Bad Code Bad Res1 Bad Res2 Bad Break Bad Numb
F-PC for DOS v3.5 (from Chris Jakeman) -18 0 0 -18 0 -4 -6 -18 -18
Win32Forth v3.5 -2 -2 0 -2 -18 -2 -2 -16 -6
GForth for Unix v0.3.0 (from Bernd Paysan) -4 -4 0 -4 -16 -3 -6 -3 -6
GForth for Win32 v0.3.0(1) -16 -16 0 -16 -16 -16 -6 -16 -6
GForth for DOS v0.3.0 -4 -4 0 -4 -18 -3 -6 -3 -6
iForth v1.07 Linux (from Marcel Hendrix) -3 -3 0 -3 -20 -3 -3 -11(2) -11
mxForth v2.4 Linux (from Marcel Hendrix) -7 -7 0 -7 -20 -7 -7 -11(2) -11
4tH v3.5a (from Hans Bezemer) -2 -2 0 -2 0 -2 -6 -14 -2

The Win32 results are much worse than the Unix ones due to a bug in the cygwin32 library, not GForth.
Under NT it is not possible to achieve -11, but only -14.