Below the warning for all occurrences of the iso codes.
/builds/php-8.4.14/ext/mbstring/libmbfl/filters/mbfilter_utf8.c:728:38: warning: initializer-string for array of ‘char’ truncates NUL terminator but destination lacks ‘nonstring’ attribute (3 chars into 2 available) [-Wunterminated-string-initialization]
728 | static const char nflags_s[10][2] = {"CN","DE","ES","FR","GB","IT","JP","KR","RU","US"};