svn commit: r290711 - head/sys/ofed/drivers/infiniband/core

[David Chisnall]

On 13 Nov 2015, at 08:35, Konstantin Belousov <kostikbel at gmail.com> wrote:
> 
> On Fri, Nov 13, 2015 at 09:18:54AM +0100, Hans Petter Selasky wrote:
>> Hi,
>> 
>> On 11/12/15 18:17, Conrad Meyer wrote:
>>> These should cast through (u)intptr_t rather than unsigned long.
>>> 
>> 
>> This is Linux code, and they use "unsigned long" for pointer casts 
>> everywhere, trying to not break their style.
>> 
>> BTW: I added to linux_compat.c:
>> 
>> CTASSERT(sizeof(unsigned long) == sizeof(uintptr_t));
>> 
>> And it survived my "tinderbox" build and I was surprised!
> 
> FreeBSD (at least currently) runs on two kinds of ABIs: ILP32 and LP64.
> ILP32 means that sizeof(int) == sizeof(long) == sizeof(void *) == 4.
> For LP64, sizeof(long) == sizeof(void *) == 8, while sizeof(int) == 4.
> We do not support anything else.

Note that this is not true of all downstreams.  We currently have 128 and 256-bit void*s with 64-bit longs on CHERI, and I believe that bde’s version has 32-bit longs on all platforms.  This kind of code *is* broken for us and we’d greatly appreciate people not writing new code that intentionally relies on undefined behaviour (round tripping a pointer via any integer type other than intptr_t is undefined in C), when a well-defined mechanism exists, just because Linux decides to do the wrong thing.

David