Messages in this thread | | | From | David Brownell <> | Subject | Re: [PATCH] ptrdiff_t is not uintptr_t, damnit | Date | Sun, 19 Aug 2007 17:57:56 -0700 |
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On Sunday 19 August 2007, Anton Altaparmakov wrote: > > > > ISTR we don't *have* a uintptr_t on all architectures, or that would > > be the appropriate thing to use in these 32/64 bit ABI scenarios. > > > > > >> Use unsigned long or uintptr_t instead. > > > > I suspect you mean "unsigned long long"... > > No he doesn't. "unsigned long" is guaranteed to be large enough to > hold a pointer (at least on Linux anyway).
And yet when I used that, I got compiler warnings on some systems.
ISTR that was the first solution I tried, but GCC really wanted to issue warnings. Either about casting 64-bit to pointer, or about casting it to "unsigned long", either way lost precision.
> On a 32-bit arch "unsigned long" is 32-bit and pointers are 32-bit. > > On a 64-bit archi "unsigned long" is 64-bit and pointers are 64-bit.
So with 32 bit userspace "unsigned long long" is the type to use when talking to a 64-bit kernel; and with pure 64-bit code, it's enough to write "unsigned long".
I'm fairly sure that's the root cause of the pain I recall here; but I'd have to run experiments again to verify that.
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