The newly introduced kenv() declaration in <unistd.h> causes compilation of plan9port to fail. The function is not yet in any FreeBSD release, having been added in January, 2024. Also reported upstream at https://github.com/9fans/plan9port/issues/648. 9c -O2 -pipe -march=znver1 -fstack-protector-strong -isystem /usr/local/include -fno-strict-aliasing sort.c sort.c:111:5: error: conflicting types for 'kcmp' /usr/include/unistd.h:522:6: note: previous declaration is here sort.c:205:28: error: too few arguments to function call, expected 5, have 2 /usr/include/unistd.h:522:6: note: 'kcmp' declared here sort.c:451:42: error: too few arguments to function call, expected 5, have 2 /usr/include/unistd.h:522:6: note: 'kcmp' declared here sort.c:470:46: error: too few arguments to function call, expected 5, have 2 /usr/include/unistd.h:522:6: note: 'kcmp' declared here sort.c:488:1: error: conflicting types for 'kcmp' /usr/include/unistd.h:522:6: note: previous declaration is here sort.c:514:41: error: too few arguments to function call, expected 5, have 2 /usr/include/unistd.h:522:6: note: 'kcmp' declared here mk: 9c -O2 -pipe ... : exit status=exit(1)