Regarding mark-sweep ( lazy approach ) for garbage collection in C++? -

-

i know reference counter technique never heard of mark-sweep technique until today, when reading book named "concepts of programming language".
according book:

the original mark-sweep process of garbage collection operates follow: runtime system allocates storage cells requested , disconnects pointers cells necessary, without regard of storage reclamation ( allowing garbage accumulate), until has allocated available cells. @ point, mark-sweep process begun gather garbage left floating-around in heap. facilitate process, every heap cells has indicator bit or field used collection algorithm.

from limited understanding, smart-pointers in c++ libraries use reference counting technique. wonder there library in c++ using kind of implementation smart-pointers? , since book purely theoretical, not visualize how implementation done. example demonstrate idea valuable. please correct me if i'm wrong.

thanks,

there 1 difficulty using garbage collection in c++, it's identify pointer , not.

if can tweak compiler provide information each , every object type, you're done, if cannot, need use conservative approach: scanning memory searching pattern may pointer. there difficulty of "bit stuffing" here, people stuff bits pointers (the higher bits unused in 64 bits) or xor 2 different pointers "save space".

now, in c++0x standard committee introduced standard abi implementing garbage collection. in n3225 can find @ 20.9.11 pointer safety [util.dynamic.safety]. supposes people implement functions types, of course:

void declare_reachable(void* p); // throw std::bad_alloc template <typename t> t* undeclare_reachable(t* p) noexcept;  void declare_no_pointers(char* p, size_t n) noexcept; void undeclare_no_pointers(char* p, size_t n) noexcept;  pointer_safety get_pointer_safety() noexcept;

when implemented, authorize plug garbage collection scheme (defining functions) application. of course require work of course provide operations wherever needed. 1 solution override new , delete not account pointer arithmetic...

finally, there many strategies garbage collection: reference counting (with cycle detection algorithms) , mark , sweep main different systems, come in various flavors (generational or not, copying/compacting or not, ...).


Comments

Post a Comment

Popular posts from this blog

c# - How to set Z index when using WPF DrawingContext? -

-
how set z-index drawing object when using drawingcontext.drawxxx() methods? the object drawn last have higher z index. can't change index of drawn objects. way draw in order. if using wpf (as placed tag), can use, example, canvas control. create shapes need like polyline obj = new polyline(); //... // ... set properties of obj and add them canvas uielementcollection: yourcanvasname.children.add(obj); //or yourcanvasname.children.insert(i, obj); first items of collection have higher z index. advantages in way: no need redraw on window changes, can anytime move objects , change order.
Read more

razor - Is this a bug in WebMatrix PageData? -

-
i think may have found bug in webmatrix's pagedata, not sure. concerns how pass data partial page calling page. in webmatrix documentation (tutorials, e.g. " 3 - creating consistent look ", , example code), pagedata recommended mechanism pass data between pages (e.g. content page layout page, or partial page). however have found not work other way, pass data partial page calling page. modifying or adding entries in pagedata in partial page, not seem calling page. cutting right down simplest possible example, in test page may have this: @{ pagedata["test"] = "initial entry"; } <p>before calling partial page, test value @pagedata["test"]</p> @renderpage("_testpartial.cshtml") <p>after returning calling page, test value @pagedata["test"]</p> and in _testpartial.cshtml page might have this: @{ pagedata["test"] = "modified entry"; } <p>in partial page...
Read more

visual c++ - Using relative values in array sorting ( asm ) -

-
i need sort through array , sort each individual row in array in ascending order. doesn't seem going (surprise!) keep getting hit 2 errors: a2101: cannot add 2 relocatable labels , a2026: constant expected here's sort, makes sense me, think i'm still trying implement high-lvl language techniqes assembly. there way around not being able use relative values? (the array 7 rows 9 columns, btw). mov cx, 7; cx = number of rows outer: ; outer loop walk through rows push cx mov cx, 9 mov row, cx ;rows middle: ; middle-loop walk through columns push cx sub cx, 1 ;cx = cx-1 mov column, cx ;columns inner: ;inner loop - compare , exchange column values cmp marray[row*9 + column], marray[row*9 + column+1] xchg marray[row*9 + column+1], marray[row*9 + column] ; compare , exchange values marray table inc column loop inner pop cx loop mid...
Read more