• Thorsten Kiefer <thorstenkiefer gmx.de> Mar 03 2007
• Lionello Lunesu <lio lunesu.remove.com> Mar 03 2007
• Stewart Gordon <smjg_1998 yahoo.com> Mar 04 2007

Thorsten Kiefer <thorstenkiefer gmx.de> writes:

Hi,
IMHO the compiler should be able to implicitly convert function-pointers into
delegate-pointers.
Before the delegate is passed as argument, the context-pointer is filled in.
Now when I pass a function, the context-pointer could simply be filled with
null.
A problem will be, where to store the context-pointer in a function, as it has
no context-pointer (to preserve compatibility with C).

Or the compiler could implicitly create an anonymous delegate around that
function.

Lionello Lunesu <lio lunesu.remove.com> writes:

Thorsten Kiefer wrote:
 Hi,
 IMHO the compiler should be able to implicitly convert function-pointers into
delegate-pointers.
 Before the delegate is passed as argument, the context-pointer is filled in.
 Now when I pass a function, the context-pointer could simply be filled with
null.


At the moment it can't, since delegates and function-pointers have 
incompatible calling conventions.

 A problem will be, where to store the context-pointer in a function, as it has
no context-pointer (to preserve compatibility with C).


There's another thread on that, "D 2.0 - dalegates to function"

 Or the compiler could implicitly create an anonymous delegate around that
function.


That would be a good transitional solution, but because it involves an 
extra function call, I'd still hope the delegate and function-pointer 
calling-convention can be made compatible.

L.

Stewart Gordon <smjg_1998 yahoo.com> writes:

Lionello Lunesu Wrote:

 Thorsten Kiefer wrote:
 Hi, IMHO the compiler should be able to implicitly convert 
 function-pointers into delegate-pointers.  Before the 
 delegate is passed as argument, the context-pointer is filled 
 in.  Now when I pass a function, the context-pointer could 
 simply be filled with null.


 At the moment it can't, since delegates and function-pointers 
 have incompatible calling conventions.


Well, it certainly used to work under at least some 
platform/compiler combinations.

I've looked, and it would appear to be a mere matter of whether 
a context pointer is pushed to the stack as well.  The ABI 
doesn't make it clear whether parameters/local variables are 
addressed from the bottom or the top of the stack frame.  From 
my experiment, it would appear to be the bottom.

<snip>
 That would be a good transitional solution, but because it 
 involves an extra function call, I'd still hope the delegate 
 and function-pointer calling-convention can be made compatible.


Indeed.  And one way that's been suggested is to pass the 
context pointer in a register rather than pushing it to the 
stack.

Stewart.