On 31 Jul '08, at 11:37 AM, JongAm Park wrote:
1. Whether the dataDesc is statically declared or not, although it is freed in the end of the "encode" action handler, it is still maintained and could be accessed from another message, "recover". And with the Memory browser, I could confirm that the memory content was still there. Why is it so? Does the NSData or NSArray just retains them?
The free( ) call doesn't immediately overwrite the block. It's added to a free-list and will be reused later in a future malloc( ) call. However, you can't rely on that of course; accessing any data from a freed block is a bug that can lead to random crashes.
2. However, when I intentionally bzero it, the content is nullified, and the recover message sees the content as zeros. So, it is not caches in the NSArray. It seems to me that it just uses by referencing.
That's bad. It sounds like the object you create doesn't contain a copy of the struct but just a pointer to it.
5. for the data, I used dataWithBytes: length: thinking that it will copy the contents, instead of just referencing the original. However, it turns out that it just references it. I figured that out by bzeroing the original, and how it is seen in the recover function.
No, +dataWithBytes: does copy the data. It's only the "...noCopy" variants that will [possibly] use your existing buffer.
Something's fundamentally wrong with your code, in that data you think you're copying is really just being referenced through a pointer. I'm sorry, but you posted a lot of stuff and I'm not going to read through it all to debug it for you. You need to do some code review on your own.
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