Admittedly, I forgot about %f/%g and the decimal separator. I think the rest is fairly obscure (such as %lc for wide character to multibyte character translatio

Admittedly, I forgot about %f/%g and the decimal separator. I think the rest is fairly obscure (such as %lc for wide character to multibyte character translation). For integers you need %Id (variant digits) or %'d (grouping). The decimal separator is a bit of a problem for JSON generation, too. Some systems have snprintf_l, but it's not very widespread.