Pawn to king 23

Bugzilla Link	354
Created on	Apr 08, 2007 18:38
Resolution	INVALID
Resolved on	Apr 10, 2007 17:09
Version	1.00beta
OS	Linux
Architecture	PC
Attachments	indexerror.sac

Extended Description

SAC's array bounds checking is broken. Specifically, although it
may check that an array offset lies within the ravel of an array,
egregious programming errors can slip through. Consider an
array X, of shape [20,30]. These expressions produce results, instead
of index errors, even in the presence of -check b:
 X[ [4, 31] ]
 X[ [4, -3] ]
This behavior is, IM(oh, so H)O, unacceptable semantics for an array language.
Presumably, the bounds checking is being performed in idx_sel, when it should
be performed as an explicit operation earlier. If IVEO did not split 
vect2offset operations, then vect2offset would be an ideal place to 
do this.
One possible way to resolve this problem is to leave vect2offset along,
introduce an array-bounds Checker-O-Meter node, which can be optimized out
of existence when static information allows that.
The IVEO split problem remains, as does the "iv - cv" overflow-on-split 
problem. More coffee is required.