[libvirt] [PATCH] MacOS: Handle changes to args in xdrproc_t

[Doug Goldstein]

On Tue, Oct 29, 2013 at 6:28 PM, Eric Blake <eblake at redhat.com> wrote:
> On 10/28/2013 12:05 PM, Doug Goldstein wrote:
>> With Mac OS X 10.9, xdrproc_t is no longer defined as:
>>
>> typedef bool_t (*xdrproc_t) (XDR *, void *, ...);
>>
>> but instead as
>>
>> typedef bool-t (*xdrproc_t) (XDR *, void *, unsigned int);
>>
>> The rationale explained in the header is that using a vararg is
>> incorrect and has a potential to change the ABI slightly. They decided
>> to specify the exact number of parameters and for compatibility with old
>> code decided to make the signature require 3 arguments. The third
>> argument is ignored for cases that its not used and its recommended to
>> supply a 0.
>> ---
>>  configure.ac            | 41 +++++++++++++++++++++++++++++++++++++++++
>>  src/rpc/virnetmessage.c | 10 ++++++++--
>>  2 files changed, 49 insertions(+), 2 deletions(-)
>>
>
> I'd like some feedback from someone else who can actually test this on
> MacOS, as well as FreeBSD, but it does seem reasonable to get in 1.1.4.

Gave this a change a whirl on FreeBSD 9.2 and it was fine. But
obviously more testing is better.

>> +      AC_DEFINE_UNQUOTED([XDRPROC_T_ARG_COUNT], [$lv_cv_xdrproc_t_args],
>> +                         [number of arguments that xdrproc_t func ptr takes])
>
> Seems reasonable; but I'm a bit worried about accepting args=2 in the
> cases where we actually needed the varargs to pass 3.  It may be safer
> to pass 3 always, unless we have empirical evidence that uclibc will
> fail to compile if we don't limit to exactly 2 (and not just a thread
> archives where they were contemplating forcing just 2, but where I don't
> know if the thread was actually applied as a patch).

fwiw, it appears that uclibc master [1] has not gone that route so I'm
not sure what became of that thread. Hard coding our implementation to
always pass 3 arguments was my other approach that I had mentioned on
IRC but I wasn't sure about any negative repercussions on other
platforms.

[1] http://git.uclibc.org/uClibc/tree/include/rpc/xdr.h#n149

-- 
Doug Goldstein