From: Dan Gohman (dgohman_at_[hidden])
Date: 2002-08-07 12:53:30
As a solution to asserts on pointers with 64-bit platforms, I've used
a function like the following:
bool is_dereferenceable_pointer(void const* p)
unsigned long v = reinterpret_cast<unsigned long>(p);
v != -1ul // -1 is sometimes used as a special non-dereferenceable
// pointer value, for example in the return value of mmap
v >= 0x1000 // Many platforms define specific address ranges
// for valid pointers.
// For platforms without a custom check defined, we
// just check for NULL.
return p != 0;
assert(is_dereferenceable_pointer(p)); // for some pointer p
In addition to avoiding warnings with 64-bit pointers, it is
more readable IMHO than `assert(p != 0)' and it can be more
aggressive on platforms with documented address spaces.
On MIPS/IRIX, for example, pointer values start at 0x400000 and
go to 0x80000000 in 32-bit ABIs and 0x10000000000 in 64-bit ABIs.
-- Dan Gohman dgohman_at_[hidden]
Boost list run by bdawes at acm.org, gregod at cs.rpi.edu, cpdaniel at pacbell.net, john at johnmaddock.co.uk