Array question

[Henry Spencer]

In article <EbhAAgG00WBNM2PIt_ at andrew.cmu.edu> rg2c+ at andrew.cmu.edu (Robert Nelson Gasch) writes:
>What happens if I do the following? Basically I don't really understand
>*why* this works:
>
>    int *this_ptr;
>    this_ptr [0] = 1;
>    this_ptr [1] = 2;
>    . . . 
>    this_ptr [9] = 10;
>
>This works fine, but I really don't know why?? It seems you're using
>memory to store an array which was never really allocated...

Precisely correct.  What is happening is that on your machine, whatever
value this_ptr happens to get as its initial value happens to point to
some memory that you are allowed to write on.  You're scribbling on a
random piece of memory, and random things could happen as a result.

Well-designed machines try to make this a catastrophic error.
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"Read the OSI protocol specifications?  | Henry Spencer @ U of Toronto Zoology
I can't even *lift* them!"              |  henry at zoo.toronto.edu  utzoo!henry