On Fri, 15 Apr 2011 18:36:17 -0400, Tomek Sowiński <j...@ask.me> wrote:
Don napisał:
LEAKY FUNCTIONS
Define a 'leaky' pure function as a pure function which can return
heap-allocated memory to the caller, ie, where the return value or a
parameter passed by reference has at least one pointer or reference
type. This can be determined simply by inspecting the signature. (Note
that the function does not need to be immutably pure).
The interesting thing is that heap allocation inside non-leaky pure
functions behaves like stack allocation. When you return from that
function, *all* those variables are unreachable, and can be discarded en
masse. Here's an idea of how to exploit this.
THE PURE HEAP
[snip]
I'm far from being a GC expert but I think Java having identified such
cases with escape analysis just puts locally allocated objects on the
stack.
Full escape analysis requires a non-stanard object format and a
non-standard linker. Simply because, escape analysis must be a
compiler-added attribute, and the linker has to understand that. We can
get away with certain things reusing the C linker by doing things like
name mangling, but escape analysis must add far more annotations
(essentially tell how parameters and return values are linked).
I think at some point, I'd prefer D to use it's own object format and
linker, to allow both escape analysis, and to use the object format as the
import database. But that isn't likely to come from Walter, I think
someone would have to build a new compiler.
-Steve
