On Mon, 25 May 2015 23:10:17 -0700, David Kastrup <d...@gnu.org> wrote:
Keith OHara <k-ohara5...@oco.net> writes:
If I can't get the dependencies worked out I'll be tempted to skip
the macro and use scm_call_1() through scm_call_3() in place of each
of the three macro expansions.
Why? Seriously. 10.04 is not even supported by Ubuntu itself any more.
Phil has the Ubuntu. I had an old RedHat installation with gcc updated as far
as I could to 4.6. In the next few weeks I'll find some reasonably-modern
linux.
The tricky bit about the function template in Smob_base
template <SCM (Super::*pmf)(void)> static SCM smob_trampoline (SCM self)
is the way it creates functions in Smob_base that call member functions of the
derived classes like Listener. Following what happens requires a lot of
flipping back and forth between header files.
It took me quite a while to figure out why you register with scm_set_smob_apply() a
static member function of Smob_base<Listener> rather rather than something in
Listener directly. After a while I concluded that the goal was to put the trampoline
code all in one place. This seemed odd as the general-case (four cases) trampoline
outnumbered the use cases.
You might want to expand the macro in-place, and follow each expansion with the
definition of the trampoline function -- or let the routine implementing "apply
smob" be a static member function, so it serves as its own trampoline. Hundreds of
times, even. Once for every Smob-derived class, even.
It's just the balance between code duplication and obfuscation.
I have a patch cooking that will convert hundreds of Scheme callbacks to
member functions with that technique. Part of the reason is to get
argument type checks in for stuff like
(ly:grob::stencil-height 0)
which just segfaults right now. Having a member function instead of a
static member makes the code simpler while the static template generated
by this technique does the typechecking while creating a this-pointer
from an SCM. And if you call the member function via C++ with an
existing instance pointer, you bypass the typechecking.
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