Hi ALex,

On 1/8/21 12:14 PM, Alejandro Colomar (man-pages) wrote:

Hi Michael,

On 1/8/21 11:50 AM, Michael Kerrisk (man-pages) wrote:

quoted

Hi Alex,

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

quoted

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.

Well, I'm not thinking of a global edit right now (we've had enough of
those for now I think :), but more as something to think for the future.
So yes, a discussion about if we prefer to have a single way of
expressing FTM or if there are times when the other way is better would
be good.
Your thoughts?

On reflection, I think the final form that I have shown may be
preferable.

Thanks,

Michael


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