On 10/1/07, Greg Ewing email@example.com wrote:
Adam Olsen wrote:
Refcounting is fairly firmly ingrained in CPython, but there are conservative GCs for C that mostly work,
Unfortunately, "mostly works" isn't good enough for something to be incorporated into CPython. It needs to work completely reliably and very portably.
Indeed. An example of how they can fail would be python linking the boehm GC (which overrides malloc and free), then dynamically loading python from another app. By the time boehm overrides malloc and free they've already been used significantly.
Another example is any sort of custom allocator. At best the conservative GC will see their heap as a single giant object (and be unable to release objects within it). At worst (if they allocate the heap via mmap rather than the overridden malloc) it won't even know the heap exists, not include it in the root set, and prematurely free objects it references.
-- Adam Olsen, aka Rhamphoryncus