garbage collector c++

Question

I've been trying to create a garbage collector in c++, i've designed it as a base class to all of mine, called garbageCandidate, which holds a static vector containing pointers to garbageCandidate with every garbageCollector instance pushing "this" on the vector.

Then a static function comes and delete all the pointers in the static vector.

At the very begining of the deleting function (delete on first pointer) i get an error stating delete was used on invalid pointer...

Does this have to do with static/dynamic binding? I mean : is the delete operator unable to act as expected since i call delete on a "father" class and it is in fact a child ?

Could a way of avoiding this be to create virtual destructors? (or a virtual delete function)?

or did i completely missed something?

ps:all objects used for test where created dynamically.

Did you make the dtor virtual in your `garbageCandidate` class? — Jerry Coffin, Apr 09 '13 at 22:05
That would only be a problem if the destructor is not `virtual`. But it's hard to say without seeing any code. Can you come up with an [SSCCE](http://sscce.org/)? — Joseph Mansfield, Apr 09 '13 at 22:05
If you are deleting derived objects through pointers-to-base, then the base destructor must be virtual. — Oliver Charlesworth, Apr 09 '13 at 22:06
Make sure you *never* create garbage-collected objects on the stack. — David Schwartz, Apr 09 '13 at 22:08

score 0 · Accepted Answer · edited May 23 '17 at 12:12

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Is there a reason you're rolling your own custom garbage collector? If all your objects are created dynamically, then why aren't you using boost's smart pointers (like boost::shared_ptr) which essentially uses RAII to give you a well tested garbage collection solution?

I ask because usually in the course of software development life cycle of a project, you end up fixing bugs in the code you wrote yourself (most of the time, at least). So is there a reason you're re-inventing the wheel?

edited May 23 '17 at 12:12

Community

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answered Apr 09 '13 at 22:37

Carl

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Because he wants to make something better. – peterh Dec 02 '13 at 22:18
We should know this mentality and help it - or at least let it in peace - even if we have other ideals. – peterh Dec 05 '13 at 16:44
shared_ptr is not a "garbage collection solution". – xryl669 Sep 12 '14 at 14:56

score 0 · Answer 2 · edited May 23 '17 at 12:21

Rather than rolling your own GC, I think you should be using the Boehm Conservative GC or smart pointers. Neither is perfect:

The Boehm Collector requires you to use special allocate and (if you use it) deallocate methods, and getting existing libraries to play along can require some effort:
- C++ standard library and Boehm garbage collector
- Is it possible to use Boehm garbage collector only for the part of the program?
Smart pointers add an overhead each time that you assign a pointer to a variable. They don't deal with object networks that have pointer cycles in them. You need to manually break the cycles to allow the objects reachable from them to be collected.

In spite of this, either of Boehm GC or Smart pointers would be less implementation and maintenance effort than rolling your own solution.

Boehm GC periodically crawls the whole stack & heap to find occurrences of our malloced pointers. It will think a memory fragment is allocated, even if its pointer is only a random composition of some nonpointer data. And it crawls data, too. I think, the only reason behind BoehmGC is that there is currently no better opensource c/c++ garbage collector. It needs to be written. — peterh, Dec 05 '13 at 16:51

garbage collector c++

2 Answers2