On 14/03/2013 09:47, Jonas Maebe wrote:
On 14 Mar 2013, at 01:48, Xiangrong Fang wrote:
The document said it is "deprecated"? Also, I want this to be cross
platform, not for unix only. The use case is:
try
buf := GetMemory(1024);
size := 10240;
stream.Read(buf^, size);
except
??
end;
That use case is a textbook example of why you should never try to
catch and handle access violations, except possibly if you then warn
the user that anything could happen if he continues (including erasing
all files on his hard drive, if he's very unlucky).
An access violation often indicates that memory has been corrupted.
Catching the access violation does not undo the memory corruption, it
just informs you about this fact. If you continue after catching the
exception in the above program, you will be working with corrupted
memory, which means that the behaviour of your program becomes
completely unpredictable afterwards.
@Xiangrong
In fact (after I saw the screenshot, that indeed the alloc mem is less
than the read), there is a possibility that the above good does NOT even
crash. Yet it corrupts memory and the app will crash at a random later
point.
If the 1024 bytes happen to be allocated in such way that they are
followed by other already alocated memory, then they can be accessed
without SigSegV.
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