"Larry Evans" <cppljevans@cox-internet.com> wrote in message news:dq3b38$sme$1@sea.gmane.org...
On 01/11/2006 09:56 AM, Achilleas Margaritis wrote:
"Larry Evans" <cppljevans@cox-internet.com> wrote in message [snip]
gc_ptr() { if this not within last created object then {
This test, IIUC, requires access to a global object (pointer to last created object or something similar). Wouldn't this then require synchronization between threads; hence, cause a big slowdown for each gc_ptr creation?
If the pointer stack is thread-specific storage, then synchronization is not be needed.
Ah, yes. I failed to remember you first post mentioned:
a) each garbage-collected thread shall have its own pointer stack allocated as thread-local-storage. The size of the pointer stack shall be analogous to the size of the hardware stack for the size of pointer of the machine.
Now, wouldn't this require the gc_ptr::CTOR to *never* take a raw pointer? This is because to test:
this not within last created object
within gc_ptr::CTOR, the pointee to the last created object would have to be stored in some thread-local-storage by another gc_ptr, and the only way this could happen is if the first gc_ptr first:
1) allocated the storage for the pointee 2) stored the last-created-pointer in some thread-local-storage 3) created the pointee with placement new (this requiring knowlege about the pointee's CTOR) 4) then zeroed the last-created-pointer
Does this make sense? [snip]
No, the new object will be placed in a thread-local-storage list by operator new. Here is the sequence of operations: 1) operator new is invoked: it allocates memory for the new block and places the block in a thread-local-storage object list. 2) gc_ptr::CTOR is invoked: it looks at the last entry of the thread-local-storage object list. If not inside that block, it adds itself to the thread-local-storage pointer stack.
_______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost