Re: static member functions vs. member function pointers
* James Kanze:
On Apr 30, 4:07 am, "Alf P. Steinbach" <al...@start.no> wrote:
* James Kanze:
As I said, I've never seen it used in correct code, period.
In pure C++, there are two widespread solutions: a callback
interface, using virtual functions, from which the client
code derives, and functional objects passed to a template.
About the only time I've seen anything else has been when
interfacing to legacy API's, in C, and in such cases, you
can't pass a static member function either, because the
callback function must have "C" linkage.
Well you can. Just not with standard's blessing. I think it
would be difficult to find a compiler that with the proper
option (usually default) doesn't support it.
Sun CC generates a diagnostic, and as far as I know, you can't
turn the diagnostic off.
Have you tried
-erroff=badargtype2w
?
And I've used C++ compilers where it
simply didn't work;
Well I still think it would be difficult to find such a compiler!
the reason the standard doesn't allow it is
because there are cases where it won't work.
Yes. But aren't those are the cases where you (or someone else) have chosen for
C++ and C to have different calling conventions?
Note that Windows, or at least VC++, is a bit special here,
because the compiler doesn't use the standard mechanism for
linkage specification. Rather, it separates linkage into two
separate parts: name mangling (specified by ``extern "..."'')
and calling conventions (specified by Microsoft extensions, e.g.
__cdecl, __stdcall, __fastcall, etc.). These extensions do
apply to static member functions. Also, the compiler does
require that a pointer to a function and the function have the
same calling conventions. And the system functions, at least,
requre different calling conventions than the default, so you
have to use Microsoft's extensions if you're going to use a
function as a callback for Windows.
Yes. I've always thought that both the standard's approach and Microsoft's
approach are horrible, in this regard. It would be nice to be able to specify
such things via C++0x attribute notation. :-)
Cheers,
- Alf
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