Hi Michael, [[ SYNOPSIS #include <stdlib.h> int clearenv(void); Feature Test Macro Requirements for glibc (see fea‐ ture_test_macros(7)): clearenv(): /* Glibc since 2.19: */ _DEFAULT_SOURCE || /* Glibc <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE ]] [[ SYNOPSIS #include <time.h> int dysize(int year); Feature Test Macro Requirements for glibc (see fea‐ ture_test_macros(7)): dysize(): Since glibc 2.19: _DEFAULT_SOURCE Glibc 2.19 and earlier: _BSD_SOURCE || _SVID_SOURCE ]] Which one do you prefer? Thanks, Alex -- Alejandro Colomar Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/ http://www.alejandro-colomar.es/