On Wed, Mar 20, 2019 at 09:53:33PM +0900, Sergey Senozhatsky wrote: > Not all compilers have __builtin_bswap16() and __builtin_bswap32(), > thus not all compilers are able to compile the following code: > > (__builtin_constant_p(x) ? \ > ___constant_swab16(x) : __builtin_bswap16(x)) > > That's the reason why bpf_ntohl() doesn't work on GCC < 4.8, for > instance: nack to fixes to support such old compilers.