On Friday, 22 September 2017 at 03:26:36 UTC, Mike Parker wrote:
On Friday, 22 September 2017 at 02:22:46 UTC, Josh wrote:
src\mixer.d(80,22): Error: function pointer
Mix_ChannelFinished (extern (C) void function(int channel)) is
not callable using argument types (extern (C) void
delegate(int channel))
Code:
void unmuteAfterPlaySound()
{
Mix_ChannelFinished(&channelDone);
}
extern (C) void channelDone(int channel)
{
unmuteMusic();
}
The error message indicates that `channelDone` is a member of a
class or a struct. A pointer to a member function is a delegate
(or closure), not a function pointer. Free functions, static
nested functions, and static member functions all produce
function pointer. Non-static member functions and non-static
nested functions all produce delegates/closures. See the docs:
https://dlang.org/spec/function.html#closures
If you need to manipulate instance members from a C callback,
you'll need a way to implement a mechanism to work out which
instance you need.
Perfect, that's the info I needed. As these functions were in a
class, setting channelDone and unmuteMusic to static worked.
As an aside, in that doc it says "The .funcptr property of a
delegate will return the function pointer value as a function
type". So I also tried
Mix_ChannelFinished((&channelDone).funcptr); and this compiled,
but caused a segfault when
the callback ran. What would have caused this? Is it because it's
a C function?
