Re: array bounds checking

glen herrmannsfeldt <gah@ugcs.caltech.edu>
3 Dec 2005 16:23:39 -0500

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Re: array bounds checking sudeshc@noida.hcltech.com (Sudesh Chandna, Noida) (2005-11-29)
Re: array bounds checking gah@ugcs.caltech.edu (glen herrmannsfeldt) (2005-12-03)
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From: glen herrmannsfeldt <gah@ugcs.caltech.edu>
Newsgroups: comp.compilers
Date: 3 Dec 2005 16:23:39 -0500
Organization: Compilers Central
References: 05-11-121 05-11-135
Keywords: code, debug
Posted-Date: 03 Dec 2005 16:23:39 EST

Sudesh Chandna, Noida wrote:


> This can be easily done by having a data structure commonly known as
> "descriptor" for pointer which can hold lower bound, upper bound, stride
> corresponding to all dimensions of the array. Also descriptor should have rank
> ( dimension ) and address of the array. Now for languages such as FORTRAN
> where its possible to say


> Ptr => ary(1:10:2)


> Descriptor values lower bound would be 1
> Upper bound would be 5
> Stride would be say 8 (2*size of element)
> Rank would be 1
> And addr will hold starting address.


Ones I know store the virtual origin, the address of element (0,...,0).
It makes it easy to do the calculation, multiply the strides by the
subscripts and add. (After checking bounds.)


-- glen

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