Re: memory management and productivity

[Martin Krischik <krischik@users.sourceforge.net>]

Bjï¿œrn Persson wrote:

> David Starner wrote:
> 
>> The only library garbage collectors I know about are conservative; they
>> assume that every pointer-size chunk of accessible memory is a pointer,
>> (unless it's in a block of data that was allocated with a special
>> function that tells the GC there are no pointers in that data.) They
>> don't move memory because you can't adjust pointers if you can't tell
>> pointers from integers. A garbage collector that was part of the compiler
>> could tell integers from pointers (that is, be a precise collector
>> instead of a conservative collector) and could move items in memory
>> (which many high-performance GCs do.) This makes easier, for example, for
>> a compiler to scan only the new stuff, which has a shorter live time than
>> the stuff the program has kept around for a while. The first may be more
>> important; a misplaced integer could potentially hold several megabytes
>> of garbage in memory.
> 
> I see. For a language like Ada, something that can't tell a pointer from
> an integer clearly isn't as good as it could be. I knew there had to be
> some drawback with a garbage collector that works for C. :-)

BTW: In an Ada dialect with a precise collector Unchecked_Convertion between
Access and Address/Integer are likely not to work any more.

And if you use Unchecked_Deallocation you need to use pragma Controlled as
well.

Both of which will break existing code :-(.

Martin

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