Why uninitialized pointers cause mem access violations close to 0?

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Category:Languages

It is said that often (but not always) when you get an AV in a memory location close to zero (like $89) you have an uninitialized pointer.
But I have seen this also in Delphi books... Hm... or they have been all written by the same author(s)???


Update:
Quote from "C++ builder 6 developers guide" by Bob Swart et all, page 71:

When the memory address ZZZZZZZZZ is close to zero, the cause is often an uninitialized pointer that has been accessed.

Why is it so? Why uninitialized pointers contain low numbers? Why not big numbers like $FFFFFFF or plain random numbers? Is this urban myth?

 


This is confusing "uninitialized pointers" with null references or null pointers. Access to an object's fields, or indexes into a pointer, will be represented as an offset with respect to the base pointer. If that reference is null then the offsets will generally be addresses either near zero (for positive offsets) or addresses near the maximum value of the native pointer size (for negative offsets).

Access violations at addresses with these characteristic small (or large) values are a good clue that you have a null reference or null pointer, specifically, and not simply an uninitialized pointer. An uninitialized reference can have a null value, but may also have any other value depending on how it is allocated.

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