cc -pthread   -Wall -Wextra -Werror=implicit-function-declaration PATH_MAX_XOPEN.c -o PATH_MAX_XOPEN -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE -lm -lpthread -lrt  -lgdbm_compat -lcrypt -latomic
PATH_MAX_XOPEN.c: In function ‘main’:
PATH_MAX_XOPEN.c:9:25: error: ‘_XOPEN_PATH_MAX’ undeclared (first use in this function)
    9 |         if ( PATH_MAX < _XOPEN_PATH_MAX )
      |                         ^~~~~~~~~~~~~~~
PATH_MAX_XOPEN.c:9:25: note: each undeclared identifier is reported only once for each function it appears in