My humble apologies. When I was writing this I was not thinking
straight.

What I actually meant was a long double, not a long pointer. So for
something declared as

long double ld;

or

void foo(long double);

what is the corresponding type specification in FFI?

On Feb 20, 12:46 pm, Wayne Meissner <wmeiss...@gmail.com> wrote:

> Do you mean, a C function with a signature something like:
>     void foo(long *l):
>
> In that case, the corresponding ruby-ffi would be:
> module MyLib
>     extend FFI::LIbrary
>     ffi_lib 'mylib'
>     attach_function :foo, [ :pointer ], :void
> end
>
> and you would invoke it like so:
>
>     ptr = FFI::MemoryPointer.new(:long)
>     ptr.write_long(0xdeadbeef)
>     MyLib.foo(ptr);
>
>     # now extract the value the C code filled in
>     l = ptr.read_long