On 07/06/2011 08:45 AM, Eric Blake wrote:
#define _SDT_ARGARRAY(x) (__builtin_classify_type (x) == 14 \ || __builtin_classify_type (x) == 5)
Too bad gcc doesn't document this builtin.
It's documented in the Internals manual: http://gcc.gnu.org/onlinedocs/gccint/Varargs.html http://gcc.gnu.org/viewcvs/trunk/gcc/typeclass.h?view=markup
So perhaps you could copy that macro and let your compatibility casting do something like this:
#define _SDT_CAST(x) \ __builtin_choose_expr (_SDT_ARGARRAY(x), (uintptr_t)(x), (x))
That depends on gcc - so we'd have to provide a fallback define to a plain cast for other compilers. I'll keep that in mind if the current patch for libvirt (which doesn't use any gcc extensions) proves to be problematic.
Well, sdt.h itself uses such extensions, so you may not get far with very different compilers anyway. But FWIW, it seems to work fine on F15's clang-2.8.
And we may still end up defining away the problem, by just stating that libvirt requires systemtap 1.4 or newer before libvirt will use systemtap.
I wouldn't blame you, if you can get away with that. We think the current version of SDT is more sane overall, with better flexibility as well as better resulting metadata. Josh