Re: Moving data into dynamic storage

[Barbara Morris <bmorris@xxxxxxxxxx>]

Rich Duzenbury wrote:
>
> At 01:52 PM 11/22/02, you wrote:
>
> >Clearly, MOVEL is inappropriate since you don't often really know
> >how much storage is actually allocated.
>
> Not so clearly to me.  I ran a test and set the length of 'entry' to be one
> byte, thinking that the movel might overrun the buffer, but it does
> not.  Only the first byte of storage got loaded, according to debug.
>

MOVEL will copy data up to the declared length of the result.

D fld2          s        50a
D result        s       100a  based(p)
c        alloc    10       p
c        movel    fld2     result

This will copy all 50 bytes of fld2 to 'result'.  The 40 bytes following
your 10 allocated bytes could be something important, and overwriting
them could cause many different bad things to happen.

Declaring the based result-field to be 1 byte would not cause this kind
of storage-corruption problem, since you can't allocate less than 1
byte.