pointer <-> integer conversion warnings (bogus -Wall warnings)

[Tom Lord <lord at emf dot net>]

So, there's a warning about:

	cast to pointer from integer of a different size

which gets set off even if there is an explicit cast.  rth suggests:

	x = (void *)(size_t)y

and I think that's pretty nice.  One can safely assume that `size_t'
is small enough not to overflow a pointer type and the double cast
(aside from being easy to grep for) means "Yes, I really mean to
truncate the integer if necessary before casting it to a pointer."

Now, what about this one:

	cast from pointer to integer of a different size

The code in question, once again, has an explicit cast:

	x = (int)p;

I am assured by the flow through my program that the value stored in
`p' was first cast from an integer and that it's range is sufficiently
constrained that it won't cause a problem on any even vaguely sane
architecture.   I added the cast to the code precisely to eliminate
the warnings and to signal that there's a possible value truncation
here that can't be disproven by the compiler -- but I want that
well-defined conversion anyway.

There is no integer type guaranteed to be wide enough to hold values
from pointers.  So unlike the first warning I asked about, I don't see
any reasonable "double cast" that solves the problem.

Have I overlooked something or is -Wall giving a bogus warning?

-t