Hi Alex,

On 1/7/21 6:04 PM, Alejandro Colomar (man-pages) wrote:

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?

Probably the latter, since it is a little easier to read.

The former form has crept in as a result of my attempts
to keep the FTM info somewhat compact. See, for example:

       chroot():
           Since glibc 2.2.2:
               _XOPEN_SOURCE && ! (_POSIX_C_SOURCE >= 200112L)
                   || /* Since glibc 2.20: */ _DEFAULT_SOURCE
                   || /* Glibc <= 2.19: */ _BSD_SOURCE
           Before glibc 2.2.2:
               none


       waitid():
           Since glibc 2.26:
               _XOPEN_SOURCE >= 500 || _POSIX_C_SOURCE >= 200809L
           Glibc 2.25 and earlier:
               _XOPEN_SOURCE
                   || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
                   || /* Glibc <= 2.19: */ _BSD_SOURCE

The latter could be rewritten (I hope I got the expansion right) 
as:
       waitid():
           Since glibc 2.26:
               _XOPEN_SOURCE >= 500 || _POSIX_C_SOURCE >= 200809L
           Glibc 2.20 to 2.25
               _XOPEN_SOURCE ||  _POSIX_C_SOURCE >= 200809L
           Glibc 2.12 to 2.19
               _XOPEN_SOURCE ||  _POSIX_C_SOURCE >= 200809L
                   || _BSD_SOURCE
           Glibc 2.11 and earlier:
               _XOPEN_SOURCE || _BSD_SOURCE

 
That's more verbose, but perhaps also easier to read, now that
I look at it.

I'm not sure whether you are thinking of doing some global edit,
but if you are, perhaps we need to discuss this more.

Thanks,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/