Uninitialized Arrays and GC

Mr. Anonymous mailnew4ster at gmail.com
Fri Dec 23 12:36:45 PST 2011

On 23.12.2011 21:51, bearophile wrote:
> Mr. Anonymous:
>> http://dlang.org/memory.html#uninitializedarrays
>> It's said here ^ that:
>> "The uninitialized data that is on the stack will get scanned by the
>> garbage collector looking for any references to allocated memory."
>> With the given example of: byte[1024] buffer = void;
>> So does the GC really scan this byte array? Or (sounds more logical to
>> me) does it scan only reference types?
>> If the latter is true, I think the example should use some kind of a
>> pointer array. Also, in this case, I can't see why "Uninitialized data
>> can be a source of bugs and trouble, even when used correctly."?
>> If the former is true, then, well, I'll ask more questions.
> The current D GC is not precise, so I think the current DMD+GC scan this array. Future better compilers/runtimes probably will be able to avoid it (with a shadow stack the gives precise typing information at runtime, used by a precise GC).

Well, if that's really so, then it's not 100% reliable.
e.g. you generate an array of random numbers, and one of them appears to 
be an address of an allocated array. This array won't free even if not 
used anymore.

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