What free and commercial garbage collection libraries are available for C++, and what are the pros and cons of each?
I am interested in hard-won lessons from actual use in the field, not marketing or promotional blurb.
There is no need to elaborate on the usual trade offs associated with automatic garbage collection, but please do mention the algorithms used (reference counting, mark and sweep, incremental, etc.) and briefly summarise the consequences.
I use boehm-gc a lot. It is straight-forward to use, but the documentation is really poor. There is a C++ page, but its quite hard to find.
Basically, you just make sure that every class inherits from their base class, and that you always pass gc_allocator to a container. In a number of cases you want to use libgccpp to catch other uses of new and delete. These are largely high-level changes, and we find that we can turn off the GC at compile-time using an #ifdef, and that supporting this only affects one or two files.
My major problem with it is that you can no longer use Valgrind, unless you turn the collector off first. While turning the collector off is easy to do, and doesn't require recompiling, it's obviously impossible to use it if you start to run out of memory.
You can also use Microsoft's Managed C++. The CLR and the GC are very solid and used in server products, but you have to use CLR types for the GC to actually collect - you can't just recompile your existing code and remove all the delete statements.
I would rather use C# to write brand new code, but Managed C++ lets you evolve your code base in a more progressive manner.