On Thu, 3 Jul 2008, Chris Lattner wrote: > is much better than some mismash of version checking, which isn't guaranteed > to be right in the future. One disadvantage of this is that it will put even > more burden on the already overloaded preprocessor. It would be much nicer to > have a feature query system that doesn't rely on one macro per system. > Perhaps something like: > > #if __feature_supported(nested_functions) && > __feature_supported(transparent_union) && > __feature_supported(attribute_aligned) > ...
This looks rather like a reinvention of the #assert system (which is deprecated, or at least recommended against in the manual). > Taking an approach reduces startup time of the preprocessor, because it > doesn't have to populate the identifier table with tons of predefines. I'd hope this is not a significant cost (certainly not compared to the thousands of built-in functions on some target), though I haven't seen recent figures for startup costs. We have some existing practice for feature macros (__GNUC_GNU_INLINE__, __GNUC_STDC_INLINE__, __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1, ...). -- Joseph S. Myers [EMAIL PROTECTED]
