KennyTM~ wrote:
The best solution I can think of, without compiler modification is a
struct/class that contains a static array member T[1024] and a dynamic
array member T[] initialized to null; and the code chooses which member
to use in the constructor. But this always occupies 1024*T.sizeof bytes
and there will always be a conditional (if) sticked to all access methods.
This entire discussion gets me thinking - could an alternate stack be a
good (or even better) solution? Consider a global per-thread
"superstack" - a growable region that allocates memory in large chunks
and makes sub-chunks accessible in a strictly LIFO manner. The
primitives of the superstack are as follows:
void* SuperStack.allocate(size_t bytes);
void SuperStack.free(size_t bytes);
size_t SuperStack.slack();
The SuperStack's management is a singly-linked list of large blocks. The
slack function returns how many bytes are left over in the current
chunk. If you request more than slack bytes, a new chunk is allocated
etc. A SuperStack can grow indefinitely (and is susceptible to leaks).
Some convenience functions complete the picture:
T[] SuperStack.array(T)(size_t objects);
enum Uninitialized { yeahIKnow }
T[] SuperStack.array(T)(size_t objects, Uninitialized);
Freeing chunks should not be done immediately in order to avoid
pathological behavior when a function repeatedly allocates and frees a
chunk just to fulfill some small data needs.
With the SuperStack in place, code could look like this:
void foo(in size_t s)
{
auto a = SuperStack.array(int)(s, Uninitialized.yeahIKnow);
scope(exit) SuperStack.free(s);
... play with a ...
}
Is there interest for such a thing?
Andrei
