>>105923245indeed indeed.
but I prefer to macro guard my code to make sure missing extensions are diagnosed nicely (not that I have ever released code of mine into the wild)
what I wonder in your example: why the computed gotos, wouldn't a simple switch have sufficed?
picrel is the latest switch I've written, interpreting strings as integers on my little endian machine for quick string comparison. kw is a union with fields char [8] and uint64_t.
so I guard the programme with CHAR_BIT == 8 and __LITTLE_ENDIAN