How can this possibly work?!

BlitzMax Forums/BlitzMax Programming/How can this possibly work?!

Leiden

(Posted 2006) [#1]

Local t:Byte Ptr = MemAlloc(1024)
t[0] = 100
t[1027] = 10

Print t[1027]

Again, its referencing outside of whats allocated. And it doesn't give any warnings in debug.

A pointer just points to the first block of memory of a certain size, an array just points to the first element right? So I'm indexing the pointer, so shouldnt t[1027] be out of bounds?

ziggy

(Posted 2006) [#2]

T has no 'maximum size' or bounds, you're using array indexing as a memory offset (it is a real pointer). Not a very elegant practicle, spetially in managed languages as BlitzMax. It can even be dangerous if you modify anynithing.

tonyg

(Posted 2006) [#3]

I think it's for the same reason given to you 10 months ago here .

Leiden

(Posted 2006) [#4]

I thought it was something like that. But how come debug wont warn you about it at least. I'm sure Visual Studio would.

Brendane

(Posted 2006) [#5]

No, Visual Studio (in which I presume you mean the VC++ runtime libraries) won't warn you either. (although there are 3rd party bounds checking systems available).

The issue with using a pointer is that you as the programmer are responsible to know what you are pointing at and how much of that memory is valid.