On Wed, 03 Mar 2010 10:34:48 -0500, Steve Teale
<[email protected]> wrote:
On Wed, 03 Mar 2010 01:38:58 -0500, Robert Jacques wrote:
On Wed, 03 Mar 2010 01:00:46 -0500, Steve Teale
<[email protected]> wrote:
* Binding a delegate to a function pointer will always need a
(dynamic) thunk, because the function will have been invoked without
any context pointer and it's the thunk's responsibility to assign the
correct context pointer.
At present, D's way of handling delegates requires patching GCC for the
GDC implementation. If an ABI change was made it would be nice if it
fitted into the GCC trampoline model.
Steve
Um, how exactly? I just read the wikipedia page on GCC trampoline and it
a) targeted only at nested functions b) utilizes self-modifying code
which is disabled on any sensible platform c) would require dynamic
allocation and d) actually uses more memory than D's method. Some time
ago there was a link to an excellent article (by Walter? Don?) on
different ways to do this. I remember d's way coming out the best, but
I've seemed to have lost the link.
I'm just quoting from something I noticed a couple of days ago. In David
Friedman's make file for GDC there is:
# Enables correct implementation of delegates. This requires patching
GCC.
D_EXTRA_DEFINES += -DD_NO_TRAMPOLINES=1
Steve
I think that's because GCC's internal nested function AST construct would
normally use trampolines, but D defines them as delegates (IIRC). As this
hack is around GCC's AST handling and not D's ABI, it would be required
regardless. BTW nested function support is a language extension specific
to GCC.
