>> bin[x][y] = 0;
>
>don't you mean bin[x]->[y] ? after all, this is a pointer to an array of
No, the original is correct. bin[x]->[y] is not legal syntax.
When you have a pointer, you can use it in a few different ways:
Suppose you have "char *p;"
*p is the value at the address that p points at
p[x] treats the address in p as the base of an array, and extracts
element x. p[0] is the same thing as *p.
p[x] is the same as *(p+x) but remember that x is multiplied by the size of the
data type to get a real address. So, if you have "int *p", p[0], p[1], etc
are the successive integers in the array.
p->y is a structure reference. y can only be a field name from the structure.
It cannot be an expression.
So, what we have here is "unsigned char **bin;"
The type of bin is unsingned char **.
The type of bin[x] is unsigned char *. It is element x of the array of
pointers.
The type of bin[x][y] is unsigned char. It is element y of the array
based at the address stored in bin[x].
>> Thanks for all the responses. You have given me a lot to think about.
>> The applicable code I am using looks similar to below. The array being
>> used is a 2D array and I used a routine I found on the internet to
>> create the array using malloc. Any further comments that might show
>> problems would be appreciated. The code shown runs most of the time
>> without problems. I have never had a crash during creation of the
>> array of during initialisation. Problems (seg. faults) seem to happen
>> at later stages after the array has been used a few times. Perhaps the
>> problem is in another area and the array is an easy target (because of
>> the size) for another code messing with the memory??
I don't see anything obviously wrong with the code snippet. The symptoms
described here are typical of something going wrong somewhere else and
corrupting the pointers in the array.
Mark S.
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