This reverts commit 755cc644cc.
This approach is problematic in several ways. First, `intptr_t` could
cause undefined behavior in the subtraction when the pointer converts to
a negative value. Except in weird cases where the sign of the pointer
identifies a memory domain (like kernel vs userspace) I'm unaware of any
valid use of `intptr_t`.
Second, this macro was created to address a special need that cannot
rely on defined behavior: i.e. to ensure that data definitions are
placed in contiguous space and access is provided through linker-defined
symbols, for which the language required alignment and continuity is not
guaranteed.
A macro that calculates the span between linker symbols has very
different semantics than one that calculates the difference between
pointers. Replace the global PTR_DIFF with a documented local macro
that tests what's necessary without risking integer overflow.
Signed-off-by: Peter A. Bigot <pab@pabigot.com>
765c06376c