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/