On Mon, Nov 1, 2021 at 9:30 AM Shanshan He <he83...@gmail.com> wrote: > > Hello, I'm reading the GC code recently, but I didn't find any code about > analyzing whether an object is reachable or not (or say whether a pointer is > live), can someone give me some hints? > > I see that each heap word corresponds to a heapBits. By doing & operation > with bitscan and bitPointer we can judge whether it has more pointers and > whether it is a pointer, but do we need to judge whether a pointer is live? > For example, we apply for a piece of memory in a function, do some > calculations through a pointer, and then return from the function, assuming > that this piece of memory is useless. In the next GC, how to determine that > the pointer in this function is dead and we can reclaim this memory?
To answer your last question first, the GC determines that a pointer is dead by marking all live pointers. Once that is done, any unmarked pointer is dead. The process of marking live pointers is done by marking memory starting from roots, where roots are global variables and live pointers on goroutine stacks. The code for this is complex, of course, but all the key steps can be found in the source file runtime/mgcmark.go. Hope that helps. Ian -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/CAOyqgcX3ig7880w6d6dvpz5idDu%2BmhCToR6ik1c%3D_rpSUwgJeA%40mail.gmail.com.
