Re: Garbage Collection - The Trash Begins To Pile Up

Walter Bright <>
29 Dec 2006 19:34:06 -0500
Ion Gazta?aga wrote:

That's not my case (I generally spend more time designing and fixing
logic errors than fixing memory leaks) but couldn't this be fixed with
an integrated leak detector? If C++ offers an standard leak detector
for special debug builds (saying where and when was memory allocated
and not freed, or reused after being freed) you can solve most of your
problems and also detect logic errors (for example if calling delete[]
frees more resources like sockets, files...). IBM/Rational Purify
(garbage collection based, I think) is a good example for this
(although it's very slow). ?Will garbage collection will fix buffer
overruns or access to uninitialized memory? If the main purpose is to
avoid leaks, let's have a leak detector.

I've used leak detectors with C/C++ for 20+ years. The first generally
available (and still available) one is one I wrote and gave away 20
years ago: They certainly help debug
memory allocation problems - but they don't make it any easier to
*design* robust memory management. They also don't guarantee correctness:

1) if you don't have a 100% comprehensive test suite
2) for every path an exception might take through your code
3) for threading issues
4) for code you have to work with that cannot be instrumented
5) for code you have to work with that uses different memory management

If we also need some memory allocation with uncertain lifetime, let's
have a garbage collected allocation method/pointer. But that's not the
same as making the whole language (new/delete) garbage collected.

I'm not suggesting that C++ be made gc. There's too much water under
that bridge. What I'm doing is countering the false notions that GC is
only for the incompetent programmer, that correct explicit memory
management is easy, that GC has nothing to offer for elite programmers, etc.

P.S. I've implemented malloc and friends, malloc debuggers, multiple
garbage collectors, garbage collector debuggers, and more custom
allocators than I can recall.

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