From: Helge Deller
Sent: 19 September 2017 21:08
...
quoted
Using 'unsigned long' for any kind of pointer is an accident
waiting do happen.
It also makes it difficult to typecheck the function calls.
Using 'void *' isn't any better.
Either a pointer to an undefined struct, or a struct containing
a single 'char' member, is likely to be safest.
=20
David, you might be right in most cases, but in this case I'd prefer
unsigned long too. I think this will create the least amount of
typecasts here.
I've not looked at the specifics case...
Another option is using a struct with a single member and
passing it by value.
This could be used for things like user-space pointers or
even errno values.
The only problem is old ABI where even small structures are
always passed by reference.
David