Re: [Blitz-support] Bug(?) -- index placeholders and non-base-zero arrays

[Patrik J. <co...@fa...>]

Hi Christopher,

Yeah, found it. It turns out the 1-D index unit-stride evaluator used
data()+lbound() which is incorrect since data() already points to the
lbound() object. So they were written into memory at the wrong place,
which also explains the memory error. This Could you do me a favor and
add this as a bug in the issue tracker so I can refer to it in the
commit. Assuming this doesn't break anything else I can push the fix
asap.

thanks for finding that,

/Patrik

On Wed, Nov 23, 2011 at 11:07 PM, Christopher Subich
<cs...@ma...> wrote:
> I've encountered a bug in the latest hg versions of Blitz, index
> placeholders are not working properly when an array is non-base-zero.
>  From what I can tell, they begin operating from the "zero element" of
> the array rather than the base, and this will lead to out-of-bounds
> memory writes.
>
> This error is not caught by -DBZ_DEBUG.
>
> Test code:
>
> int main() {
>    Array<double,1> bar(3); // c-Array
>    Array<double,1> qux(3,fortranArray); // fortran
>    Array<double,1> foo(Range(5,7)); // custom
>    blitz::firstIndex ii;
>    // Indexed assignment from 0
>    bar = ii;
>    cout << bar;
>    // FortranArray
>    qux = ii;
>    cout << qux;
>    // Indexed assignment on non-base-0
>    foo = ii;
>    cout << foo;
>    return 0;
> }
>
> Expected output (older version of Blitz, $Id: indexexpr.h,v 1.7
> 2005/05/07 04:17:56 julianc Exp $)
> (0,2)
> [ 0 1 2 ]
> (1,3)
> [ 1 2 3 ]
> (5,7)
> [ 5 6 7 ]
>
>
> Current output: (hg checkout on 23 Nov 2011)
> (0,2)
> [ 0 1 2 ]
> (1,3)
> [ 0 1 2 ]
> (5,7)
> [ 0 0 0 ]
>
> Those last two assignments also cause memory errors.  Valgrind will
> scream, and re-ordering the source statements can cause a segfault.
>
> I'm not too familiar with the innards of Blitz, so I can't begin to
> debug this myself.  Unfortunately, this bug is a show-stopper for me
> since my code relies on the proper working of this bit.
>
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