digitalmars.D.learn - How to instantiate class object NOT in the GC heap
- Alexandr Druzhinin (5/5) Jul 15 2012 Hello,
- =?UTF-8?B?QWxleCBSw7hubmUgUGV0ZXJzZW4=?= (30/35) Jul 15 2012 This is how you do it in modern D:
- Alexandr Druzhinin (2/27) Jul 15 2012 how to pass arguments to ctor of class A?
- =?UTF-8?B?QWxleCBSw7hubmUgUGV0ZXJzZW4=?= (7/44) Jul 15 2012 You pass those after the 'mem' argument to emplace. So, for example:
- Alexandr Druzhinin (2/4) Jul 15 2012 thanks for your help!
- bearophile (7/8) Jul 15 2012 This seems fiddly and bug-prone (and eventually fit to go in the
- =?UTF-8?B?QWxleCBSw7hubmUgUGV0ZXJzZW4=?= (9/16) Jul 15 2012 malloc is guaranteed to allocate on a machine word boundary which I
- Jonathan M Davis (7/13) Jul 15 2012 It'll probably become easier to do once we have allocators, since it'll=
- Benjamin Thaut (91/103) Jul 15 2012 emplace has quite some issues especially when it can't find any
- Jonathan M Davis (14/34) Jul 15 2012 om
Hello, I need something like that - http://digitalmars.com/techtips/class_objects.html, but more portable. I saw it sometime ago, but now can not find anything. Could someone help me.
Jul 15 2012
On 15-07-2012 15:43, Alexandr Druzhinin wrote:Hello, I need something like that - http://digitalmars.com/techtips/class_objects.html, but more portable. I saw it sometime ago, but now can not find anything. Could someone help me.This is how you do it in modern D: import core.stdc.stdlib, std.conv; class A {} void main() { // allocate and initialize auto size = __traits(classInstanceSize, A); auto mem = malloc(size)[0 .. size]; auto a = emplace!A(mem); // a is now an instance of A in the libc heap. // finalize and deallocate clear(a); free(mem.ptr); // or free(cast(void*)a); } clear() calls the finalizer on the object you give it. In the case of A, there is no finalizer, so it doesn't matter. It would matter if you had something like: class A { private void* resource; ~this() { freeResource(resource); } } -- Alex Rønne Petersen alex lycus.org http://lycus.org
Jul 15 2012
15.07.2012 20:50, Alex Rønne Petersen пишет:This is how you do it in modern D: import core.stdc.stdlib, std.conv; class A {} void main() { // allocate and initialize auto size = __traits(classInstanceSize, A); auto mem = malloc(size)[0 .. size]; auto a = emplace!A(mem); // a is now an instance of A in the libc heap. // finalize and deallocate clear(a); free(mem.ptr); // or free(cast(void*)a); } clear() calls the finalizer on the object you give it. In the case of A, there is no finalizer, so it doesn't matter. It would matter if you had something like: class A { private void* resource; ~this() { freeResource(resource); } }how to pass arguments to ctor of class A?
Jul 15 2012
On 15-07-2012 16:46, Alexandr Druzhinin wrote:15.07.2012 20:50, Alex Rønne Petersen пишет:You pass those after the 'mem' argument to emplace. So, for example: auto a = emplace!A(mem, "foo", bar, 'b', 'a', 'z'); -- Alex Rønne Petersen alex lycus.org http://lycus.orgThis is how you do it in modern D: import core.stdc.stdlib, std.conv; class A {} void main() { // allocate and initialize auto size = __traits(classInstanceSize, A); auto mem = malloc(size)[0 .. size]; auto a = emplace!A(mem); // a is now an instance of A in the libc heap. // finalize and deallocate clear(a); free(mem.ptr); // or free(cast(void*)a); } clear() calls the finalizer on the object you give it. In the case of A, there is no finalizer, so it doesn't matter. It would matter if you had something like: class A { private void* resource; ~this() { freeResource(resource); } }how to pass arguments to ctor of class A?
Jul 15 2012
15.07.2012 22:03, Alex Rønne Petersen пишет:You pass those after the 'mem' argument to emplace. So, for example: auto a = emplace!A(mem, "foo", bar, 'b', 'a', 'z');thanks for your help!
Jul 15 2012
Alex Rønne Petersen:This is how you do it in modern D:This seems fiddly and bug-prone (and eventually fit to go in the D FAQ). Maybe it needs to use an aligned_malloc, to avoid aligning troubles in the class. Bye, bearophile
Jul 15 2012
On 15-07-2012 18:34, bearophile wrote:Alex Rønne Petersen:malloc is guaranteed to allocate on a machine word boundary which I think is sufficient. Bug-prone? Sure. But I don't think there's much we can do about that without language support... -- Alex Rønne Petersen alex lycus.org http://lycus.orgThis is how you do it in modern D:This seems fiddly and bug-prone (and eventually fit to go in the D FAQ). Maybe it needs to use an aligned_malloc, to avoid aligning troubles in the class. Bye, bearophile
Jul 15 2012
On Sunday, July 15, 2012 18:34:44 bearophile wrote:Alex R=C3=B8nne Petersen:It'll probably become easier to do once we have allocators, since it'll= =20 probably become possible to do something like auto alloc =3D getMallocAllator(); auto obj =3D alloc.make!T(args1, args2, args3); - Jonathan M DavisThis is how you do it in modern D:This seems fiddly and bug-prone (and eventually fit to go in the D FAQ). Maybe it needs to use an aligned_malloc, to avoid aligning troubles in the class.
Jul 15 2012
Am 15.07.2012 21:06, schrieb Jonathan M Davis:On Sunday, July 15, 2012 18:34:44 bearophile wrote:emplace has quite some issues especially when it can't find any constructor to call you have no clue whats happening. Here is my custom new which does quite some special case handling: auto New(T,ARGS...)(ARGS args) { return AllocatorNew!(T,StdAllocator,ARGS)(StdAllocator.globalInstance, args); } string ListAvailableCtors(T)() { string result = ""; foreach(t; __traits(getOverloads, T, "__ctor")) result ~= typeof(t).stringof ~ "\n"; return result; } auto AllocatorNew(T,AT,ARGS...)(AT allocator, ARGS args) { static if(is(T == class)) { size_t memSize = __traits(classInstanceSize,T); static assert(!__traits(compiles, { T temp; bool test = temp.outer !is null; }), "inner classes are not implemented yet"); } else { size_t memSize = T.sizeof; } void[] mem = allocator.AllocateMemory(memSize); debug { assert(mem.ptr !is null,"Out of memory"); auto address = cast(size_t)mem.ptr; auto alignment = T.alignof; assert(address % alignment == 0,"Missaligned memory"); } //initialize static if(is(T == class)) { auto ti = typeid(StripModifier!T); assert(memSize == ti.init.length,"classInstanceSize and typeid(T).init.length do not match"); mem[] = (cast(void[])ti.init)[]; auto result = (cast(T)mem.ptr); static if(is(typeof(result.__ctor(args)))) { scope(failure) { AllocatorDelete(allocator, result); } result.__ctor(args); } else { static assert(args.length == 0 && !is(typeof(&T.__ctor)), "Don't know how to initialize an object of type " ~ T.stringof ~ " with arguments:\n" ~ ARGS.stringof ~ "\nAvailable ctors:\n" ~ ListAvailableCtors!T() ); } static if(is(AT == StdAllocator)) { allocator.SetIsClass(mem.ptr); } static if(is(T : RefCounted)) { result.SetAllocator(allocator); return ReturnRefCounted!T(result); } else { return result; } } else { *(cast(T*)mem) = T.init; auto result = (cast(T*)mem); static if(ARGS.length > 0 && is(typeof(result.__ctor(args)))) { result.__ctor(args); } else static if(ARGS.length > 0) { static assert(args.length == 0 && !is(typeof(&T.__ctor)), "Don't know how to initialize an object of type " ~ T.stringof ~ " with arguments " ~ args.stringof ~ "\nAvailable ctors:\n" ~ ListAvailableCtors!T() ); } return result; } } Kind Regards Benjamin ThautAlex Rønne Petersen:It'll probably become easier to do once we have allocators, since it'll probably become possible to do something like auto alloc = getMallocAllator(); auto obj = alloc.make!T(args1, args2, args3); - Jonathan M DavisThis is how you do it in modern D:This seems fiddly and bug-prone (and eventually fit to go in the D FAQ). Maybe it needs to use an aligned_malloc, to avoid aligning troubles in the class.
Jul 15 2012
On Sunday, July 15, 2012 21:14:40 Benjamin Thaut wrote:Am 15.07.2012 21:06, schrieb Jonathan M Davis:t'llOn Sunday, July 15, 2012 18:34:44 bearophile wrote:Alex R=C3=B8nne Petersen:=20 It'll probably become easier to do once we have allocators, since i=This is how you do it in modern D:This seems fiddly and bug-prone (and eventually fit to go in the D FAQ). Maybe it needs to use an aligned_malloc, to avoid aligning troubles in the class.omprobably become possible to do something like =20 auto alloc =3D getMallocAllator(); auto obj =3D alloc.make!T(args1, args2, args3); =20 - Jonathan M Davis=20 emplace has quite some issues especially when it can't find any constructor to call you have no clue whats happening. Here is my cust=new which does quite some special case handling:Well, if you have suggestions on how to improve emplace, then please cr= eate an=20 enhancement request and/or a pull request. And with properly written cu= stom=20 allocators, all of the special casing should then be _in_ the allocator= where=20 you won't have to deal with it, making it so that you'd only really nee= d=20 emplace directly when you're doing something that none of the custom=20= allocators will do (or you're writing your own custom allocator). - Jonathan M Davis
Jul 15 2012