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digitalmars.D.learn - Is there a way to combine "Free Lists" and "Explicit Class Instance Allocation"

Try my luck here.

== Repost the article of z (z gg.com)
== Posted at 2008/08/15 20:36 to digitalmars.D

== Quote from z (z gg.com)'s article
 Hi,
 I'm reading http://digitalmars.com/d/2.0/memory.html
 and try to combine "Free Lists" and "Explicit Class Instance Allocation".
 So instead of:
 void test()
 {
     Foo f = Foo.allocate();
     ...
     Foo.deallocate(f);
 }
 I can just write as normal:
 void test()
 {
     Foo f = new Foo();
     ...
     delete Foo;
 }
 But the simple code I wrote seg faults. Is this a compiler bug? or I'm doing
 something wrong? or can this thing be done at all?
 Thanks.
  << custom.d >>

the code: $ cat custom.d import std.stdio; import std.c.stdlib; import std.outofmemory; import std.gc; class Bar { public void fun() { printf("Bar\n"); } } class Foo : Bar { string name; this() { printf("my ctor\n"); } ~this() { printf("my dtor\n"); // suppose I don't do anything here } public override void fun() { writeln(name); } new(size_t sz) { printf("my new\n"); Foo f; if (freelist) { f = freelist; freelist = f.next; return cast(void*)f; // I know that ctor will be called again on f. Is there any way to skip :-) ? } void* p; p = std.c.stdlib.malloc(sz); if (!p) throw new OutOfMemoryException(); //std.gc.addRange(p, p + sz); return p; } delete(void* p) { printf("my del\n"); // suppose I just save it for reuse, instead of free memory Foo f = cast(Foo)p; deallocate(f); printf("saved!\n"); // try to call some method, see if it still works: f.fun(); // Segmentation fault here. Is there any way to make this work? // I run thru the debugger, and found f's attritube is not changed. // so what's going wrong? // is this because even after I provided my own 'delete' and '~this', // compiler still inserted some extra cleanup code? } static Foo freelist; // start of free list static void deallocate(Foo f) { f.next = freelist; freelist = f; } Foo next; // for use by FooFreeList } int main() { Foo foo; foo = new Foo(); foo.name = "old-guy"; foo.fun(); delete foo; foo = new Foo(); foo.fun(); return 0; }
Aug 16 2008