[Digikam-devel] [Pkg-kde-extras] Bug#396747: FTBFS (alpha): attempt to use output operater '<<' on va_list

Steve Langasek vorlon at debian.org
Fri Nov 3 22:29:22 GMT 2006

On Fri, Nov 03, 2006 at 06:17:36PM +0000, Mark Purcell wrote:
> Also, i suspect than va_list type is unknow on Alpha. This type is defined by 
> libtiff. Perhaps header files from this library are different between i386 
> and Alpha. 

This is wrong.  Falk already explained why it was failing: va_list is an
*opaque type* per the C standard, you are not allowed to cast it, print it,
dereference it, or assign to it in standards-compliant code.  The only legal
operations are va_copy(), va_start(), va_end(), and va_arg().

The reason that non-standard operations work on some other architectures
but not on alpha has to do with the C function calling conventions on the
different archs, but that's not all that relevant; the bottom line is that
you will never have a << operator for va_list that works on alpha.  Which
means that the proposed workaround -- eliminating the debug statements that
try to output va_list -- is actually the correct fix.

Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
vorlon at debian.org                                   http://www.debian.org/

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