cc -pthread  -Wall -Wextra -Werror=implicit-function-declaration fcntl/posix_fadvise.c -o fcntl/posix_fadvise -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm -lpthread  -liconv
fcntl/posix_fadvise.c:14:16: error: call to undeclared function 'posix_fadvise'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
   14 |         if ( (errno = posix_fadvise(fileno(fp), 0, 2, POSIX_FADV_SEQUENTIAL)) )
      |                       ^
fcntl/posix_fadvise.c:14:48: error: use of undeclared identifier 'POSIX_FADV_SEQUENTIAL'
   14 |         if ( (errno = posix_fadvise(fileno(fp), 0, 2, POSIX_FADV_SEQUENTIAL)) )
      |                                                       ^
2 errors generated.